Adrenoleukodystrophy: a rare metabolic disorder characterized by damage of the myelin sheaths in the nervous system and degeneration of the “adrenal glands.” It leads to progressive neurologic disorders, adrenal insufficiency and death. (NCIt) An “X-linked” disorder characterized by the accumulation of saturated very long chain “fatty acids” in the “lysosomes” of the “adrenal cortex” and the “white matter” of the “central nervous system.” This disease occurs almost exclusively in males. (MeSH) Lack of a “peroxisome” "enzyme" gradually prevents processing of fats needed to make “myelin” which somehow affects “microglia.” “Gene therapy” fixes “bone marrow” cells outside the body, which are then injected into the bloodstream. They find their way to the brain, where they give rise to corrected microglia. The “viral vector” is “HIV,” stripped of the genes that cause “AIDS.” (Lewis, 402)

Agraphia: an acquired inability to write, although the strength and coordination of the hand remains normal. Related to disorders of “language” and caused by disease in the ”parietal lobe.” (OxfordMed) Loss or impairment of the ability to write (letters, syllables, words, or phrases) due to an injury to a specific cerebral area or occasionally due to emotional factors. This condition rarely occurs in isolation, and often accompanies “aphasia.” (MeSH) Also referred to as "dysgraphia."

Alice in Wonderland Syndrome: a disorder in which people experience a distorted sense of their hands or faces. (Blakeslee, 211) Characterized by disturbances in visual "perception," most often of “body schema,” time perception and “hallucinations.” It is associated with migraine, “infections,” "fever," “epilepsy,” and other neurological and psychiatric disorders. (MeSH)

Alien Hand Syndrome: disorder in which a person’s hand seems to have a mind of its own. (Blakeslee, 24) Feeling that the limb is not one’s own and is being controlled by someone else. (Hawkins, 200) The feeling that one’s hand is possessed by an uncontrollable outside force resulting in its actual movement. Usually stems from an injury to the “corpus callosum” or “anterior cingulate.” (RamachandranTTB, 294) The hand is running on its own inaccessible programs, and that is why it’s branded as ‘alien’ because the conscious part of the patient seems to have no predictive power over it. (Eagleman, 131) Also referred to as ‘alien limb syndrome.’

Amnesia: systematic and extensive loss of “memory” caused by organic or psychological factors.The loss may be temporary or permanent, and may involve old or recent memories. (NCIt) A condition in which memory is impaired or lost. (OxfordMed) Abnormal forgetting caused by various forms of brain disease. (Goldberg, 109) Unusual forgetfulness. One may not be able to remember new events, recall one or more memories of the past, or both. Normal aging may cause some forgetfulness. It's normal to have some trouble learning new material, or needing more time to remember it. However, normal aging does not lead to dramatic memory loss. Such memory loss is due to other diseases. Sometimes, memory loss may be seen with “depression.” It can be hard to tell the difference between memory loss and confusion due to depression. (PubMedHealth2) Also referred to as ‘memory loss.’

Anterograde Amnesia: the inability to acquire new memories. (OxfordMed) Loss of ability to learn new information (Goldberg, 117) A condition in which people can remember the distant past and learn new skills, but they cannot form new memories for facts and events. (Chudler, 55) The most famous case of anterograde amnesia is that Henry Gustav Molaison (1926-2008), referred to as ‘HM.’ (Hockenbury, 248) Also referred to as ‘fugue amnesia.’

Retrograde Amnesia: loss of preexisting memories. (OxfordMed) Loss of ability to recall information acquired before the damage took place. (Goldberg, 118) Loss of the ability to recall information that had been previously encoded in memory prior to a specified or approximate point in time. May be associated with trauma, accidents, “seizures,”  “dementia,” and a wide variety of other conditions that impair cerebral function. (NCIt) People who have retrograde amnesia are unable to remember some or all of their past. (Hockenbury, 248)

Temporal Gradient of Retrograde Amnesia: the concept that when memory suffers, relatively recent memories will be more affected than memories for a very distant past. (Goldberg, 11)

Anosmia: loss of the sense of smell. (Oxford) This can be temporary, as with a cold, or it can be permanent, following certain viral infections, head injuries, and "tumors" affecting the “olfactory nerve.” (OxfordMed) Affects perhaps as many as 5 percent of people (and) causes many problems. People with anosmia cannot smell gas, smoke, or rancid food. They cannot enjoy the good smells of the world, either, and they cannot enjoy many of the subtler flavors of food. (Sacks6, 83) Mutations in genes encoding “receptors” for various chemicals can lead to deficits or differences in the detection of specific odors, or the ability to taste specific compounds. (Mitchell, 134) Temporary loss of the sense of smell is common with colds and nasal allergies, such as hay fever. It may occur after a viral illness. Some loss of smell occurs with aging. In most cases, there is no obvious cause, and there is no treatment. The sense of smell is often lost with disorders that prevent air from reaching the part of the nose where smell receptors are located. (PubMedHealth2) The neurological interconnection between the sense of smell and "emotion" is uniquely intimate. The emotional health of ‘anosmic’ patients typically continues to deteriorate with passing time, in some cases requiring hospitalization. (Herz, 3-5) Without a sense of smell, our ability to know ourselves and others is obscured, our emotional world becomes deadened or disturbed, our ability to enjoy food is lost, our heath may decline, and our sexual desire is severely weakened. (Herz, xv) Also referred to as ‘smell blindness.’

Anosognosia: a patient’s lack of awareness of a brain deficit or problem. Usually caused by damage to the right hemisphere. (Goldberg, 31) Greek for ‘denial of illness.’  A syndrome in which a person who suffers a disability seems unaware of, or denies the existence of, the disability. (RamachandranTTB, 294) A total lack of awareness about an impairment. Typical example is a patient who completely denies their very obvious paralysis. (Eagleman, 135)

Aphasia: loss or impairment of the power to use or comprehend words. (Koch, 15) "Language" disorder. Includes speech disorders. Usually caused by damage to the “left temporal lobe,” “left parietal lobe,” or “left frontal lobe.” (Goldberg, 26) Commonly accompanied by difficulties in reading and writing. (OxfordMed) This condition is caused by diseases which affect the language areas of the dominant hemisphere. Clinical features are used to classify the various subtypes of this condition. General categories include ‘receptive,’ ‘expressive,’ and ‘mixed’ forms of aphasia. (MeSH)

Anomia: a particular form of aphasia which results in the loss of the use of words. Early indicator of Alzheimer’s disease. Usually caused by damage to the left hemisphere. (Goldberg, 29) The patient is unable to recall the names of everyday objects. (Oxford) A language dysfunction characterized by the inability to name people and objects that are correctly perceived. The individual is able to describe the object in question, but cannot provide the name. This condition is associated with lesions of the dominant hemisphere involving the language areas, in particular the “temporal lobe.” (NCIt)

Broca’s Aphasia: difficulty in producing language. (OxfordMed) Difficulty with “grammar,” more specifically the deep structure of language. (RamachandranTTB, 295) An aphasia characterized by impairment of expressive language (speech, writing, signs) and relative preservation of receptive language abilities (i.e., comprehension). This condition is caused by “lesions” in the frontal lobe. The deficits range from almost complete muteness to a reduction in the fluency and rate of speech. (NCIt) Paul Broca and Carl Wernicke, two physicicans, discovered that specific neurological disorders can be traced to specific regions of the brain… thus laying the groundwork for modern brain science. In the early 1860’s, Broca encountered (nine) patients… with difficulty producing language and found that they all had damage in the same area in the left side of the brain, a region that became known as Broca’s Area. (Kandel4, 10-11) Also referred to as ‘expressive aphasia,’ and ‘motor aphasia.’

Wernicke’s Aphasia: difficulty with the comprehension of the spoken word. (OxfordMed) Difficulty with comprehension and expression of meaning. (RamachandranTTB, 295) Impairment in the comprehension of speech and meaning of words, both spoken and written, and of the meanings conveyed by their grammatical relationships in sentences. (PubMedHealth) In 1875, Carl Wernicke observed the mirror image (of Broca’s Aphasia). He encountered a patient whose words flowed freely but who could not understand language (spoken to him). Wernicke tracked this deficit in language comprehension to damage in the back of the left hemisphere, a region that became known as Wernicke’s area. (Kandel4, 11) Also referred to as ‘receptive aphasia,’ and ‘sensory aphasia.’

Apraxia: a disorder characterized by the loss of the ability to carry out learned purposeful movements, despite knowing what is expected and having the physical ability and desire to do so. (RamachandranTTB, 295) Usually caused by damage, related to stoke or Alzheimer’s, to the parietal lobe - mostly in the left hemisphere. (Blakeslee, 211) Disorder of the “cerebral cortex” resulting in the patients inability to organize movements rather than clumsiness due to weakness, sensory loss, etc. (OxfordMed) A group of cognitive disorders characterized by the inability to perform previously learned skills that cannot be attributed to deficits of motor or sensory function. Apraxias are generally associated with “lesions” of the dominant “parietal lobe” and “supramarginal gyrus.” (MeSH)

Dressing Apraxia: loss of the ability to put clothes on correctly (commonly seen in dementia). (Goldberg, 25) Dressing apraxia may result from an inability to mentally formulate the act of placing clothes on the body. (MeSH)

Gait Apraxia: difficulty in walking. (OxfordMed) Impaired ambulation not attributed to sensory impairment or motor weakness. Frontal lobe disorders; Parkinsonian disorders; “dementia,” Alzheimer’s disease; and other conditions may be associated with gait apraxia. (MeSH)

Ideational Apraxia: the loss of the ability to use common objects according to their function. (Goldberg, 27) Loss of the ability to mentally formulate the processes involved with performing an action. (MeSH)

Ataxia: disorders in coordination and balance. (Blumenfeld, 34) Lack of coordination of muscle movements resulting in the impairment or inability to perform voluntary activities. Causes include peripheral nerve disorders, posterior column injuries, cerebral and cerebellar disorders, “basal ganglia” disorders, and ‘thalamic’ disorders. (NCIt) Impairment of the ability to perform smoothly coordinated voluntary movements. This condition may affect the limbs, trunk, eyes, “pharynx,”  “larynx,” and other structures. (MeSH)

Wobblers: patients who cannot stand well due to disorders in their “vestibular apparatus.” Associated with excessive dose of 'gentamicin,' an "antibiotic" that can poison inner ear structures. (Doidge, 2)

Atrophy: the wasting away of a normally developed organ or tissue due to “degeneration” of cells. (OxfordMed) Any weakening or degeneration, especially through lack of use. (NCIt) Occurs from a lack of physical activity. In most people, ‘muscle atrophy’ is caused by not using the muscles enough. People with seated jobs, medical conditions that limit their movement, or decreased activity levels can lose muscle tone and develop atrophy. (PubMedHealth2)

Audition Disorders: disorders characterized by the partial or complete loss of the ability to detect sounds due to damage to the ear structures or inability of the brain to properly interpret or process the auditory signals it receives from the anatomic structures of the ear. (NCIt)

Deafness: a general term for the complete loss of the ability to hear from both ears. (MeSH) An inherited or acquired condition characterized by a partial or complete loss of hearing in one or both ears. The level of impairment varies from a mild but important loss of sensitivity to a total loss of hearing. (NCIt) Hearing depends on specialized hair cells in the cochlea of the inner ear, which sense air vibrations and transmit that signal to the brain. Movement of these (hair) cells is detected by a complex molecular apparatus of proteins inside each cell, and other proteins forming links between cells. Some mutations that cause deafness specifically affect these proteins, while others have indirect effects on the development or survival of the hair cells or the formation of the auditory nerve. (Mitchell, 134)

Conduction Deafness: poor transfer of sounds from the eardrum to the inner ear. (Coon, 173) A (pathology) that may result if the tiny bones of the “middle ear” are damaged or become brittle, as they sometimes do in old age. Can be helped by a hearing aid, which amplifies “sounds.” (Hockenbury, 97) Occurs because of a mechanical problem in the outer or middle ear. The three tiny bones of the ear may not conduct sound properly, or, the eardrum may not vibrate in response to sound. (PubMedHealth2) Also referred to as ‘conductive hearing loss.’

Nerve Deafness: hearing loss caused by a problem in the inner ear or “auditory nerve.” Often affects a person's ability to hear some frequencies more than others. This means that sounds may be appear distorted, even with the use of a hearing aid. (NCIt) Occurs from damage to the inner ear, the auditory nerve, or the brain. The inner part of the ear contains tiny hair cells (nerve endings), that change sounds into electric signals. The nerves then carry these signals to the brain. (Nerve deafness) is caused by damage to these special cells, or to the nerve fibers in the inner ear. A “cochlear implant” may be recommended for certain people with very severe hearing loss. Surgery is done to place the implant. The implant makes sounds seem louder, but does not restore normal hearing. (PubMedHealth2) Cannot be helped by a hearing aid. Can be caused by exposure to loud noise. (Hockenbury, 98) Also referred to as ‘acquired hearing loss’ and ‘sensorineural deafness.’

Tinnitus: ringing in the ears. (Blakeslee, 84) Medical term for ‘hearing’ noises in your ears when there is no outside source of the sounds. Tinnitus is common. Almost everyone notices a mild form of tinnitus once in a while that only lasts a few minutes. However, constant or recurring tinnitus is stressful and make it harder to focus or sleep. It is not known exactly what causes a person to ‘hear’ sounds with no outside source of the noise. However, tinnitus can be a symptom of almost any ear problem. (PubMedHealth2) An almost nonstop hissing or ringing sound that often goes with hearing loss, and may be intolerably loud at times. (Sacks6, 110) A disorder in which a person hears noises such as buzzing, ringing, clicking, or the sound of a pulse, when no outside sound is causing them. Tinnitus may have many different causes, and may be a symptom of another disease or condition. It may be caused by certain tumors and anticancer drugs. (NCIt) A sensation of noise (as a ringing or roaring) that is caused by a bodily condition (as a disturbance of the auditory nerve or wax in the ear) and typically is of the subjective form which can only be heard by the one affected. (GHR) A nonspecific symptom of hearing disorder characterized by the sensation of buzzing, ringing, clicking, pulsations, and other noises in the ear. (MeSH)

Gaze Tinnitus: when patients with this disorder look to the left (or right), they hear a ringing sound. When they look straight ahead, nothing happens. (Ramachandran, 37)

Objective Tinnitus: refers to noises generated from within the ear or adjacent structures that can be heard by other individuals. (MeSH)

Subjective Tinnitus: when the sound is audible only to the affected individual. (MeSH)

Autoscopy: an experience of disembodiment in which people see themselves as doubles. (Blakeslee, 212) Illusion of a person’s own body appearing in front of them. (Blakeslee, 105)

Body Integrity Identity Disorder: condition in which people desperately want to amputate perfectly healthy limbs. (Blakeslee, 212) Neurological disorder in which an otherwise mentally competent person desires to have a healthy limb amputated in order to 'feel whole.' (RamachandranTTB, 295) Also referred to as ‘amputee wannabe’ and ‘apotemnophilia.’

Somatoparaphrenia: (characterized by) the patient’s vehement denial of ownership of her own left arm and insistence that it belongs to someone else. (RamachandranTTB, 19)

Canavan Disease: a rare neurodegenerative condition of infancy or childhood characterized by “demeylination.” (An enzyme) deficiency leads to an accumulation of ’N-acetylaspartic acid.’  “Inheritance” may be “autosomal recessive” or the illness may occur sporadically. This illness occurs more frequently in individuals of Ashkenazic Jewish descent. (MeSH) Robs neurons of their “myelin sheaths” so that the brain slowly degenerates. (Lewis, 388) Lack of the enzyme (‘aspartoacylase’) disrupts the interaction between neurons and “oligodendrocytes.” Without the enzyme, N-acetylaspartatic acid builds up and destroys the oligodendrocytes. (Lewis, 400) Symptoms usually begin in the first year of life. Parents tend to notice when a child is not reaching certain developmental milestones, including head control. Symptoms include poor muscle tone, especially of the neck muscles, poor visual tracking or blindness, and severe intellectual disability (PubMedHealth2)

Chronic Fatigue Syndrome (CFS): unexplained persistent or relapsing chronic fatigue that is of at least six months' duration, is not the result of ongoing exertion, is not substantially alleviated by rest, and results in substantial reduction of previous levels of occupational, educational, social, or personal activities. (NCIt) Severe, continued tiredness that is not relieved by rest and is not directly caused by other medical conditions. There is currently no cure for CFS. The goal of treatment is to relieve symptoms. Many people with CFS have "depression" and other psychological disorders that may improve with treatment (PubMedHealth2) A disabling, relentless exhaustion (which) usually begins with a flu-like illness, and lasts at least six months. People with CFS make too little of the stress hormone “cortisol,” and too much of the nervous system chemical “serotonin,” which induces sleep and calms mood. Hormones from the “hypothalamus,”  “pituitary gland,” and “adrenal glands,” control responses to trauma. Three genes have variants that differ in people with CFS. One gene encodes the receptor that binds stress hormones, and the other two affect the availability of serotonin. (Lewis, 149)

Chronic Traumatic Encephalopathy (CTE): the progressive brain degeneration seen in people who have suffered repeated concussions. (Kandel4, 168) A very rare disorder that is not yet well understood. CTE has a complex relationship to head traumas such as post-concussion syndrome and second impact syndrome that occur earlier in life. Experts are still trying to understand how repeated head traumas — including how many head injuries and the severity of those injuries — and other factors might contribute to the changes in the brain that result in CTE. Has been found in the brains of people who played football and other contact sports, including boxing. It may also occur in military personnel who were exposed to explosive blasts. Some signs and symptoms of CTE are thought to include difficulties with thinking (cognition), physical problems, emotions and other behaviors. It's thought that these develop years to decades after head trauma occurs. CTE cannot be made as a diagnosis during life except in those rare individuals with high-risk exposures. Researchers do not yet know the frequency of CTE in the population and do not understand the causes. There is no cure for CTE. (Mayo)

Cognitive Disorders: interference or disruption of cognitive processes. This term encompasses a large number of problems and issues associated with intellectual functioning and information processing. Also, a category of psychiatric disorders which are characterized by a deficit in cognition or memory. (NCIt) It is important to note that many of the aspects of cognitive functions that don’t require memory mature quite well. Wisdom and perspective certainly increase with age. Anxiety tends to decrease. (Kandel4, 117) Also referred to as ‘cognitive dysfunction.’

Age-Related Memory Loss: a disorder that is distinct from Alzheimer’s disease—it acts on different processes in a different region of the brain. Some weakening of memory, beginning around age forty, is normal. “Implicit memory” is often well preserved in old age, even in the early stages of Alzheimer’s disease. That’s because the disease does not affect the amygdala, the cerebellum, or other areas important for implicit memory until quite late in its course. It also explains why people who are unable to recall the names of loved ones can still ride a bicycle, read a sentence, and play the piano. In contrast, “explicit memory” degrades early in people with Alzheimer’s disease. Involves the “dentate gyrus,” a structure within the hippocampus. It is likely that ‘osteocalcin’ (a hormone) released by the bones, ameliorates age-related memory loss in people. (Kandel4, 115-117) Also referred to as ‘benign senescent forgetfulness.’

Dementia: loss of the ability to think, remember, learn, make decisions, and solve problems. (NCIt) Chronic and progressive deterioration of behavior and higher intellectual function due to organic brain disease. Marked by memory disorders, changes in personality, deterioration in personal care, impaired reasoning ability, and disorientation. (OxfordMed) A condition in which a person loses the ability to think, remember, learn, make decisions, and solve problems. Symptoms may also include personality changes and emotional problems. Dementia usually gets worse over time. (NCI1) Acquired and persistent syndrome of intellectual impairment characterized by memory and other cognitive deficits and impairment in social and occupational functioning. (Kolb, 590) The dysfunction is multifaceted and involves memory, behavior, personality, judgment, attention, spatial relations, language, abstract thought, and other executive functions. The intellectual decline is usually progressive. (MeSH) Author’s note - includes Alzheimer’s Disease.

Frontotemporal Dementia: a syndrome caused by progressive degeneration of the frontal or temporal lobes of the brain. It is manifested with personality changes and deterioration of the language skills. (NCIt) Alzheimer’s disease is not the only common dementia. Another common form is frontotemporal dementia. We now know that it and Alzheimer’s disease account for most cases of dementia in people over the age of sixty-four. Generally begins at a younger age and progresses more rapidly than Alzheimer’s disease. (Kandel4, 125) A tragic disease in which the frontal and temporal lobes degenerate. With the loss of the brain tissue, patients lose the ability to control hidden impulses. These patients unearth an endless variety of ways to violate social norms; shoplifting, removing clothes in public, running stop signs, eating food scraps found in public trash cans, or being physically aggressive. (Eagleman, 155) Commonly results in profoundly disordered social behavior and moral reasoning. People may commit uncharacteristic antisocial acts, such as shoplifting. Such behavior is not characteristic of people with Alzheimer’s disease. Also affects the parts of the brain that allow us to relate to others. People with this disorder who were once loving and kind may become indifferent to those around them. They also become vulnerable to addiction. This dementia has a huge impact on families because it affects people in midlife, many of whom have children. The biological mechanism is the same as that of Alzheimer’s disease. But some of the genes responsible for the protein misfolding are different in each disorder. The three mutated genes responsible for frontotemporal dementia are the gene that codes for the ‘tau protein,’ the ‘C90RF72 gene,’ and the gene that codes for ‘progranulin,’ a protein with several roles in the brain. Each mutated gene damages the same region of the brain, and each does it by means of abnormal protein folding. (Kandel4, 126-127)

Senile Dementia: a dementia of old age. (OxfordMed) Loss of intellectual abilities in an elderly person, interfering with this person's activities. (NCIt) Adjective - ‘senile.’ Also referred to as ‘senility.’

Mild Cognitive Impairment: memory or other impairments that prevent (individuals) from sustaining an independent lifestyle.  Well before an individual receives an MCI label, their brain is already well down the path of growing the Alzheimer's disease pathology. (Merzenich, 5) A phase of cognitive decline that may precede the emergence of Alzheimer’s disease and other “dementias. It may include impairment of cognition, such as impairments in “language,” (visual and spatial) "awareness," “attention” and memory. (MeSH)

Cotard Syndrome: a disorder in which a patient asserts that he or she is dead, even claiming to smell rotting flesh or worms crawling over the skin. It may be an exaggeration of the “Capgras syndrome,” in which not just one sensory area (such as face recognition) but all sensory areas are cut off from the “limbic system,” leading to a complete lack of emotional contact with the world and with oneself. (RamachandranTTB, 298) Also referred to as ‘walking corpse syndrome.’

Demyelination: the state resulting from the loss or destruction of myelin; also: the process of such loss or destruction. (GHR) Loss or dysfunction of myelin in the central or peripheral nervous system. (MeSH) Damage to the myelin sheath, the protective covering that surrounds nerve cells. When this nerve covering is damaged, nerve signals slow down or stop. (PubMedHealth2)

Dyscalculia: loss of computational skills. (Goldberg, 27) Struggling to do math. (Fischer, 32) Many patients with dyscalculia also have an associated brain disorder called “finger agnosia.” (Ramachandran, 19) Impaired ability in numerical concepts. These inabilities arise as a result of (a) primary neurological lesion, or (are) acquired due to brain damage. (MeSH) Also referred to as ‘acalculia.’

Dysfunction: an abnormality or impairment of function. (Oxford) Used with organs and diseases for disordered function in disease states. (MeSH) A state of not functioning normally. Disturbance, impairment or abnormality of function. (NCIt)

Dyslexia: a developmental disorder marked by difficulty in reading, or in understanding written words. (Oxford) Trouble reading or spelling. (Fischer, 32) People struggle with linking either the visual shapes of letters to the sounds they make, or the visual shapes of words to the meanings or concepts of the words. It’s not that this can’t be done, just that it remains effortful for people with dyslexia. The heritability of dyslexia is about 50% though the genetic variants that contribute to it remain largely elusive. As with most disorders affecting neural development, what is most likely inherited is a certain probability to develop the condition. (Mitchell, 143) Selectively affects a child’s ability to learn to read and write. (OxfordMed) A learning disorder characterized by an impairment in processing written words. Reading difficulties can include distortions, omissions or substitutions of characters. Oral and silent reading difficulties can include faulty and slow comprehension. (NCIt)  Also referred to as ‘specific dyslexia,’  'developmental reading disorder,’ and ‘developmental word blindness.’

Dysphoria: a state of unease or discomfort; especially an unpleasant state of mind marked by malaise, depression, or "anxiety." The opposite of "euphoria.”  (Oxford)

Dysplasia: abnormal growth or development of body tissue. (Oxford) 

Dystonia: body map disorders involving abnormal muscle movements. Includes putting yips. (Blakeslee, 212) Syndrome dominated by involuntary, sustained or spasmodic, patterned, and repetitive muscle contractions; frequently causing twisting, flexing or extending, and squeezing movements or abnormal postures. (GHR) It most often affects the large axial muscles of the trunk and limb. (MeSH) Adjective – 'dystonic.'

Focal Dystonia: dystonia specifically confined to a small region such as the eyelids or the hand. (Blakeslee, 73)

Occupational Dystonia: experienced by players from a wide variety of sports. Experienced by musicians. Experienced by writers (‘writers cramp’). Included Alex Rodrigues and Chuck Knoblauch, (baseball), and Sam Sneed (golf). (Blakeslee, 78) 

Familial Dysautonomia: a congenital disorder caused by mutations in the ‘IKBKAP’ gene. It is characterized by damage of the “sympathetic” and “parasympathetic nervous system.” (NCIt) An “inherited” disorder that affects nerves throughout the body. A person must inherit a copy of the defective gene from each parent to develop the condition. This condition is seen most often in people of Eastern European Jewish ancestry (Ashkenazi Jews). It is rare in the general population. (PubMedHealth2) Rare genetic disorder. Reduces sensation of pain, heat, and cold. Causes “pneumonia,” (skin) rashes, and seizures. Usually results from “exon” skipping in the gene encoding an enzyme necessary for the survIval of certain neurons that control sensation and involuntary responses. (Lewis, 221-222) Also referred to as ‘Riley-Day syndrome.’

Fasciculation: brief spontaneous contraction of a few muscle fibers, which is seen as a flicker of movement under the skin. Often associated with disease of the lower motor neurons. (OxfordMed) Involuntary contraction of the muscle fibers innervated by a motor unit. Fasciculations can often be visualized and take the form of a muscle twitch or dimpling under the skin, but usually do not generate sufficient force to move a limb. They may represent a benign condition or occur as a manifestation of motor neuron disease or peripheral nervous system diseases. (MeSH) Caused by minor muscle contractions in the area, or uncontrollable twitching of a muscle group that is served by a single motor nerve fiber. Muscle twitches are minor and often go unnoticed. Some are common and normal. Others are signs of a nervous system disorder. (PubMedHealth2) Also referred to as ‘muscle twitching.’

Giant Axonal Neuropathy: (characterized by) giant "axons" (that) stifle nerve transmission, affecting the ability to move. An affected individual is wheelchair-bound by adolescence, and does not survive his or her twenties. Caused by (mutations in a gene coding for) a key protein, ’gigaxonin,’ that is not dismantled and recycled, and instead builds up in axons, distending them. (Lewis, 29) Gigaxonin is involved in a cellular function that destroys and gets rid of excess or damaged proteins. Neurons without functional gigaxonin accumulate excess neurofilaments in the axon, causing the axons to become distended. These giant axons do not transmit signals properly and eventually deteriorate, resulting in problems with movement and other nervous system dysfunction. (GHR) Characterized by the presence of abnormally large nerve cell axons. Signs and symptoms include difficulty walking, sensory disturbances, lack of motor coordination and abnormal reflexes in the limbs. (NCIt)

Hemiballismus: violent, flailing movements of a limb. (S.Goldberg, 95) Abnormal involuntary movements which primarily affect the extremities, trunk, or jaw that occur as a manifestation of an underlying disease process. (MeSH)

Huntington’s Disease: a hereditary disease with progressive brain-cell degeneration, causing spasmodic body movements and progressive dementia. (Oxford) Characterized by the progressive loss of brain and muscle function. Symptoms usually begin during middle age. The disease is inherited as an “autosomal dominant” trait, meaning that a single mutated copy of the responsible gene is sufficient to cause the disease. (NHGRI) Symptoms include uncontrolled movements, clumsiness, balance problems, difficulty walking, talking, or swallowing. The disease has a progressive course with a decline in mental abilities, and the development of psychiatric problems. (NCIt) First described in 1872 by George Huntington, a physician, who noted the hereditary nature, involuntary movements, and changes in personality and cognitive functioning that characterize the disorder. Unlike Parkinson’s disease, Huntington’s disease can lead to cognitive as well as motor defects, including sleep disorders and dementia. It primarily affects the “basal ganglia,” but it also affects the cerebral cortex, the hippocampus, the hypothalamus, the thalamus, and occasionally the cerebellum. (Kandel4, 165) Caused by a genetic defect on chromosome 4. The defect causes a part of DNA, called a ‘CAG repeat,’ to occur many more times than it is supposed to. (PubMedHealth2) The word ‘CAG’ codes for the amino acid glutamine and calls for it to be inserted into a protein when that protein is being synthesized. In Huntington’s disease a portion of the mutant gene repeats the word ‘CAG’ again and again, resulting in the insertion of too many glutamines. This expanded string of glutamines causes the protein to clump inside the neuron, killing the cell. (Kandel4, 167) (Considered a) ‘gain of function’ disorder because the “mutant” “allele” encodes a protein that prevents the normal protein from functioning in certain brain cells. (Lewis, 79) “Positional cloning” discovered the genes behind Huntington disease. (Lewis, 424)

Hyperkinetic Movement Disorder: characterized by dancelike, involuntary movements. For example, Huntington’s disease. (Blumenfeld, 34) Excessive movement of muscles of the body as a whole, which may be associated with organic or psychological disorders. (MeSH) Also referred to as ‘hyperkinesis.’

Hypokinetic Movement Disorder: characterized by movements that are infrequent, slow, and rigid. For example, Parkinson's Disease. (Blumenfeld, 34)

Multiple Sclerosis: a disorder of the central nervous system marked by weakness, numbness, a loss of muscle coordination, and problems with vision, speech, and bladder control. Multiple sclerosis is thought to be an autoimmune disease in which the body's immune system destroys “myelin.” (NCIt) A condition characterized by areas of damage (lesions) on the brain and spinal cord. These “lesions” are associated with, destruction of the covering that protects nerves and promotes the efficient transmission of nerve impulses (the myelin sheath), and damage to nerve cells. (GHR) Causes paralysis, blindness, and other sensory-motor and cognitive disabilities. Caused by defective electrical communication between neurons that results when the body’s immune system attacks the myelin sheath, stripping the electrical insulation from an axon. (Fields, 37) Because nerves in any part of the brain or spinal cord may be damaged, patients with multiple sclerosis can have symptoms in many parts of the body. (PubMedHealth2) An estimated 1.1 to 2.5 million people worldwide have multiple sclerosis. Although the reason is unclear, this condition is more common in regions that are farther away from the equator. In Canada, parts of the northern United States, western and northern Europe, Russia, and southeastern Australia, the condition affects approximately 1 in 2,000 to 2,400 people. It is less common closer to the equator, such as in Asia, sub-Saharan Africa, and parts of South America, where about 1 in 20,000 people are affected. For unknown reasons, most forms of multiple sclerosis affect women twice as often as men. (GHR)

Neuropathy: a disease or dysfunction of one or more peripheral nerves, typically causing numbness and weakness. (Oxford) Peripheral nerves carry information to and from the brain. They also carry signals to and from the spinal cord to the rest of the body. Peripheral neuropathy means these nerves don't work properly. Peripheral neuropathy may be damage to a single nerve. It may be damage to a nerve group. It may also affect nerves in the whole body. (PubMedHealth2) A nerve problem that causes pain, numbness, tingling, swelling, or muscle weakness in different parts of the body. It usually begins in the hands or feet and gets worse over time. Neuropathy may be caused by physical injury, infection, toxic substances, disease (such as cancer, diabetes, kidney failure, or malnutrition), or drugs, including anticancer drugs. (NCIt)

Neuropathic: of, pertaining to, or caused by neuropathy. (Oxford)

Neurotoxic Syndromes: the tendency of some treatments to cause damage to the nervous system. Examples of neurotoxins include chemotherapy agents, radiation treatment, heavy metals, pesticides, and food additives. (NCIt) Poisonous or harmful to nerve cells. (OxfordMed) Neurologic disorders caused by exposure to toxic substances through ingestion, injection, cutaneous application, or other method. This includes conditions caused by biologic, chemical, and pharmaceutical agents. (MeSH)

Phantom Limbs: (after loss of a limb, a patient continues) to feel a phantom (limb) with vivid sensations of movement. (Ramachandran, 1) Perception of painful and non-painful phantom sensations that occur following the complete or partial loss of a limb. The majority of individuals with an amputated extremity will experience the impression that the limb is still present, and in many cases, painful. (MeSH)

Phenylketonuria (PKU): a disorder characterized by the body's inability to break down and utilize the essential amino acid ‘phenylalanine.’ (NCIt) Results in a buildup of phenylalanine which affects the brain. (Lewis, 193) A rare condition passed down through families. Both parents must pass on the defective gene in order for a baby to have the condition. (PubMed Health2) People with the disease have two abnormal copies of the gene that is ultimately responsible for breaking down the “amino acid” phenylalanine, a component of protein in the foods we eat. If the body can’t break down phenylalanine, it builds up in the blood, leading to the production of a toxic substance that interferes with normal brain development. (Kandel4, 46) Hundreds of different “mutant” alleles pair causing profound intellectual disability. (Lewis, 91) Classical phenylketonuria presents in infancy with developmental delay; seizures; skin hypopigmentation; eczema; and demyelination in the central nervous system. (MeSH)

Prion: a protein-like structure that causes 'spongiform' brain diseases such as 'mad cow.' Recently discussed in connection with long-term memory retention. (SAM, Oct/Nov 2007, 37) Prions are formed when normal “precursor” proteins misfold. Neurons, like other cells, have internal mechanisms that monitor the shape of proteins. Usually these mechanisms compensate for mutations or damage to the cell, but as we age the mechanisms become weaker and less effective at preventing shape changes. When that happens, a mutant gene, or damage to the cell, can cause normal precursor proteins to misfold into a lethal prion conformation. The prions form insoluble clumps inside the neuron, disrupting its function and eventually killing it. What makes prions so… dangerous, is their ability to self-propagate. Prions do not need genes in order to replicate. As a result these misfolded proteins are essentially “infectious.” They can be released by affected neurons and taken up by neighboring cells, where they induce normal precursor proteins to fold abnormally, becoming prions (themselves) and ultimately killing the cells. (Kandel4, 169) Small infectious particle that lacks nucleic acids; pathogen of animals, and apparently man. (GHR) Proteins that can maintain themselves through self-perpetuation. The reason they maintain themselves is because they cause death and destruction. (However) the self-propagating form is not a killer form, but it is the good, healthy, functional form of the protein that allows (implicit) memory to be carried forward in time. (Kandel5, 13)

Rasmussen’s Encephalitis: a rare, chronic inflammatory disease. Affects to just a small bit of the brain but an entire half. Only one known treatment— a “hemispherectomy.” (Eagleman, 5)

Seizures: the physical findings or changes in behavior that occur after an episode of abnormal electrical activity in the brain. (PubMedHealth2) A brief discharge of a small group of hyper-excitable brain cells (neurons). (RamachandranTTB, 303) Seizures may be categorized according to the severity of symptoms. If seizures occur repeatedly and cannot be controlled by drug treatments, surgery may be performed. The goal of surgery is to remove damaged or scarred tissue that serves as the focal point of a seizure. (Kolb, 112)

Grand Mal Seizure: a generalized seizure disorder characterized by recurrent major motor seizures. (MeSH) A seizure resulting in lack of "consciousness." Begins in late teens. Often "familial." (RamachandranTTB, 303) The patient falls to the ground unconscious with the muscles in a state of spasm. This - the 'tonic phase' - is replaced by convulsive movements (the 'clonic phase') when the tongue may be bitten. Movements gradually cease and the patient may rouse in a state of confusion. (OxfordMed) Also referred to as 'major seizure' and 'tonic-clonic' seizure.

Petit Mal Seizure: generalized seizure that manifests in a form of a brief episode of impairment of consciousness with or without accompanying motor phenomena. (NCIt) Seen in children as a brief absence. Such seizures are completely benign and the child almost always outgrows them. (RamachandranTTB, 303) Consists of brief spells of unconsciousness lasting for a few seconds, during which posture and balance are maintained. The eyes stare blankly and there may be fluttering movements of the lids. As the stream of thought is completely interrupted, children with frequent seizures may have learning difficulties. (OxfordMed) Also referred to as 'absence seizure.'

Sensory Deprivation: prolonged perceptual isolation. In the early 1960’s, sensory deprivation tanks were designed to intensify the effect of isolation by floating the body in a darkened tank of warm water. Such immersion chambers could produced ‘altered states.’ At the time, such sensory deprivation tanks were sought out as avidly as ‘consciousness-expanding’ drugs. The tanks… produced not only visual deprivation but every other sort of deprivation— hearing, touch, “proprioception,” “movement,” and “vestibular” sensation. While the romantic use of sensory deprivation… has diminished since the 1960’s, it's political use is still horrifyingly common in the treatment of prisoners. Hallucinations (associated with sensory deprivation) can be magnified sometimes to madness, especially when combined with social isolation, sleep deprivation, hunger, thirst, torture, or the threat of death. (Sacks6, 67,70-76)

Synesthesia: condition in which a person literally perceives something in a sense besides the sense being stimulated, such as tasting shapes or seeing colors in sounds or numbers. (RamachandranTTB, 304) A disorder that blurs the distinction between the senses. (Hawkins, 198) A congenital cross-wiring of the senses that may, for example, unite perceptions of colors with tones, or images with words, or textures with tastes. (Blakeslee, 215) Condition in which normally separate sensations are joined. Tastes have shapes, numbers or letters have colors, voices have flavors, red has a smell. Some sounds can look like glass shards. In ‘emotion color synesthesia’ patient sees auras around people. (Blakeslee, 119) People with synesthesia experience additional ‘percepts’ in response to stimulation of one sense or other. They may, for example, see flashes of light or color when they hear sounds—either general sounds or specific types, like music. There are many different types—over 80 recognized so far. (They) involve different combinations of inducing stimuli (sounds, tastes, words, numbers, music, people) and different concurrent percepts (colors, sounds, tastes, odors, touch, etc. (Mitchell, 144) A congenital (and often familial) condition where there are fixed sensory equivalences that last a lifetime. The perceptual transformations and hallucinations induced by mescaline, LSD, and other hallucinogens… are creations of the moment. In this way they are quite different from true synesthesia. (Sacks6, 165)

Tay-Sachs Disease: rare inherited disorder that progressively destroys nerve cells (neurons) in the brain and spinal cord. (GHR) A life-threatening disease of the nervous system passed down through families.The disease occurs when the body lacks a protein that helps break down a chemical found in nerve tissue. Without this protein, (the chemical) builds up in cells, especially nerve cells in the brain. Tay-Sachs disease is caused by a defective gene on chromosome 15. When both parents carry the defective Tay-Sachs gene, a child has a 25% chance of developing the disease. Anyone can be a carrier of Tay-Sachs, but the disease is most common among the Ashkenazi Jewish population. About 1 in every 27 members of the Ashkenazi Jewish population carries the Tay-Sachs gene. (PubMedHealth2) Signs and symptoms include progressive deterioration of the mental and physical abilities early in life, accompanied by blindness, deafness, muscle atrophy, and paralysis. (NCIt)

Tremor: rhythmical and alternating movement that may affect any part of the body. (Oxford) The shaking movement of the whole body or just a certain part of it, often caused by problems of the neurons responsible for muscle action. (NCIt) Most often noticed in hands and arms. It may affect any body part, even (the) head or voice box. Tremors can happen at any age. They are more common in older people. Everyone has some tremor when they move their hands. Stress, fatigue, anger, fear, caffeine, and smoking may make this type of tremor worse. A tremor that does not go away over time may be a sign of a medical problem. (PubMedHealth2)

Vision Disorders: visual impairments limiting one or more of the basic functions of the eye: visual acuity, dark adaptation, color vision, or peripheral vision. These may result from eye diseases, optic nerve diseases, visual pathway diseases, occipital lobe diseases, ocular motility disorders' and other conditions. (NCIt)

Astigmatism: an abnormally curved eyeball that results in blurry vision for lines in a particular direction. (Hockenbury, 90) A hereditary condition that affects the shape of the eyeball and impairs the ability to focus visual images on the retina. This affects the spatial resolution of vision. Commonly corrected with glasses or contact lenses. (Mitchell, 135) A type of refractive error of the eye. Refractive errors cause blurred vision and are the most common reason why a person goes to see an eye professional. People are able to see because the front part of the eye is able to refract (bend) light and focus it onto the back surface of the eye, called the retina. If the light rays are not clearly focused on the retina, the images (seen) may be blurry. With astigmatism, the “cornea” is abnormally curved, causing vision to be out of focus. The cause of astigmatism is unknown. It is usually present from birth, and often occurs together with “nearsightedness” or “farsightedness.” (PubMedHealth2)

Blindness: the inability to see or the loss or absence of “perception” (visual information). (MeSH) The lack of vision. Caused by neurological or physiological factors. (NCIt) Many genetic conditions (can) cause blindness, some from birth, but more due to a progressive degeneration of the “photoreceptor cells.” (Mitchell, 135)

Charles Bonnet Syndrome: disorder causing either partial or complete blindness. Usually caused by damage to the “visual pathway.” Extremely common, affecting millions of people worldwide whose vision has become compromised by glaucoma, cataracts, macular degeneration or diabetic retinopathy. Includes cartoonist James Thurber. (Ramachandran, 87)

Color Blindness: one of several inherited forms of color deficiency or weakness in which an individual cannot distinguish between certain colors. (Hockenbury, 95) Inherited through a gene located on the X-chromosome. Females with their two X chromosomes are less likely to become color deficient because only one normal gene is required for normal color vision. (Goldstein, 212) Individuals with red-green color blindness either lack the red or green cone pigments or have them in an abnormal form. A single recessive allele from the mother will result in red-green color blindness, even though the mother herself is not color blind. (Brooker, 964) Mutations in (genes that make the protein) ’opsin’ cause three different types of colorblindness. About 8 percent of males of European ancestry are colorblind, as are 4 percent of males of African descent. Only 0.4 percent of females in both groups are colorblind. (Lewis, 117)

Farsightedness:  greater difficulty seeing near objects than distant objects. It may be caused by the eyeball being too small or the focusing power being too weak. Farsightedness is often present from birth, but children have a very flexible eye lens, which helps make up for the problem. As aging occurs, glasses or contact lenses may be required to correct the vision. (PubMedHealth2) Objects near the eyes appear blurry because light reflected off the objects is focused behind the retina. (Hockenbury, 89) Also referred to as ‘hyperopia.’

Hemispatial Neglect: difficulty attending to information appearing in one-half of the visual field. (Goldberg, 30) Where the patient loses awareness of the left half of visual space. (Caused by) damage to the left parietal lobe. (RamachandranTTB, 19) A disorder caused by damage to the parietal lobe in which one looses the ability to perceive the left half of space, the left half of his or her body, or both. (Blakeslee, 207, 213) A condition that often follows strokes in the right brain, especially in the right parietal lobe. Neglect is not blindness. Neglect patients are profoundly indifferent to objects and events in the left side of the world, sometimes including the left side of their own bodies. (Ramachandran, 114) A patient afflicted with visual neglect has difficulty attending to the information appearing in one half of the visual field – the half opposite to the hemisphere where there has been brain damage. Visual neglect is even more severe as one half of the visual field is completely ignored. (Goldberg, 30) Also referred to as ‘neglect,’ ‘one-side neglect,’ ‘visual neglect,’  hemineglect,’ ‘hemiinattention,’ an ’hemispatial inattention.’

Leber Congenital Amaurosis: an eye disorder that primarily affects the retina, which is the specialized tissue at the back of the eye that detects light and color. People with this disorder typically have severe visual impairment beginning in infancy. Leber congenital amaurosis is also associated with other vision problems, including an increased sensitivity to light (photophobia), involuntary movements of the eyes (nystagmus), and extreme farsightedness (hyperopia). The pupils, which usually expand and contract in response to the amount of light entering the eye, do not react normally to light. Instead, they expand and contract more slowly than normal, or they may not respond to light at all. Additionally, the clear front covering of the eye (the cornea) may be cone-shaped and abnormally thin. (GHR) At least eighteen different genes cause Leber. (Lewis, 89) The different forms of the disease arise because there are many ways that a mutation can disrupt the function of the cells that provide vision. (Lewis, 95) Editor’s note - Leber congenital amaurosis is an example of “genetic heterogeneity.”

Nearsightedness: the condition in which the individual does not see far distances clearly. (NCIt) Affects the properties of the lens. (Like astigmatism, this hereditary condition) impairs the ability to focus visual images on the retina and affects the spatial resolution of vision. Commonly corrected with glasses or contact lenses. (Mitchell, 135) When light entering the eye is focused incorrectly, making distant objects appear blurred. Nearsightedness is a type of refractive error of the eye. (PubMedHealth2) Distant objects appear blurry because the light reflected off the objects focuses in front of the retina. (Hockenbury, 89) Visual images come to a focus in front of the retina of the eye because of defects in the refractive media of the eye or of abnormal length of the eyeball resulting especially in defective vision of distant objects. (GHR) Also referred to as ‘myopia.’