Glossary: Commonly Used Terms Found in Medical Literature — D-H

A - C  •  D - H  •  I - M  •  N - P  •  Q - Z

DC inhibitors: Drugs that block decarboxylase, one type of enzyme that breaks down dopamine. Also called AADC inhibitors, they include carbidopa and benserazide.

Decarboxylase: A category or subclass of enzymes that removes or eliminates a molecule of carbon dioxide from a carboxylic group. Carbidopa is an inhibitor of the decarboxylation of levodopa.

Degenerative: Marked by or pertaining to deterioration; particularly, deterioration of the function or structure of tissue or changes from a higher to a lower or less functionally active form.

Deglutition: The act of swallowing

Delayed echolalia: when someone repeats the speech of somebody else hours, days, or weeks after they hear it, in an involuntary and meaningless way. People with delayed echolalia may repeat a word, phrase, or entire sentences.

Delayed on phenomenon:  A phenomenon experienced by individuals that take levodopa.  Typically this phenomenon is felt after one initially takes the levodopa and that person does not feel the immediate effects of the medication.  The effect of the medication is therefore delayed, but still felt.

Delusion: a persistent false belief that is strongly held despite clear evidence that the belief is actually false. There are many different types of delusions, depending on what the delusion is about. An example would be a person's belief that the FBI was following him/her to put him/her in jail. This is called a delusion of persecution because the person believes he/she is being persecuted against. Delusion comes from the Latin word "deludo" meaning "to play false."

Dementia: A neurological condition characterized by a progressive decline in intellectual functioning, resulting in impaired judgment, memory, and abstract thinking; disorientation; and personality disintegration. Dementia may result due to various underlying conditions, including certain neurodegenerative diseases, such as Alzheimer's disease or Huntington's disease; brain injury or tumors; inflammation of the brain (encephalitis); successive strokes; or a condition known as normal-pressure hydrocephalus, which is characterized by enlargement of cavities (ventricles) of the brain, with cerebrospinal fluid (CSF) pressure at the upper end of normal. (CSF flows through and protects the ventricles of the brain, the spinal canal, and the space between layers of the membrane [meninges] enclosing the brain and spinal cord.) Normal-pressure hydrocephalus is associated with dementia, gait disturbances, and an inability to control urination (urinary incontinence).

Dendrites: The relatively narrow, branching projections that extend from the cell bodies of neurons. Nerve cells may contain multiple dendrites, which are stimulated by neurotransmitters, receive impulses from the nerve fibers (axons) of other neurons, and convey them toward their nerve cell bodies.

Dentatorubropallidoluysian atrophy: A rare genetic disorder that is most commonly described in Japan. Associated symptoms may become apparent in adolescence or adulthood. Early-onset disease may be characterized by rapidly progressive neurodegenerative changes, including seizures, cognitive impairment, and brief, "shock-like" muscle spasms of certain muscles or muscle groups (myoclonus). Late-onset disease may be associated with progressively impaired control of voluntary movement (ataxia) and symptoms often seen in Huntington's disease (HD), including chorea and gradual loss of thought processing and acquired intellectual abilities (dementia). Brain imaging studies typically reveal degenerative changes of the globus pallidus and specialized nerve cell clusters within the cerebellum (dentate nucleus). Similar to HD, the disorder may result from abnormally long sequences or "repeats" of particular coded instructions (unstable expanded CAG repeats) within a gene (located on chromosome 12).

Detrusor: The outer muscle of the bladder wall that assists in urine output.

Detrusor hyperreflexia: Overactive bladder

Diaphragm: The dome-shaped muscle that separates the chest and abdomen. The diaphragm plays an essential role in breathing, contracting when air is drawn into the lungs and relaxing upon exhalation.

Differential diagnosis: Distinguishing between two or more diseases and conditions with similar symptoms by systematically comparing and contrasting their clinical findings, including physical signs, symptoms, as well as the results of laboratory tests and other appropriate diagnostic procedures.

Diplegia: is paralysis (loss of movement and/or sensation) of the same body part on both sides of the body or of two similar parts on opposite sides of the body. Examples of diplegia would be when both hands are paralyzed or two similar parts of the face on both sides of the body are paralyzed. There are several specific types of diplegia, depending on the body part affected.

Diuretics: Medications that promote the excretion of urine. Such medications are often prescribed to help reduce excess fluid levels in the body, such as associated with chronic heart failure, high blood pressure (hypertension), or certain kidney (renal) or liver (hepatic) disorders. Diuretics help to remove excess water from the body by increasing the amount that is excreted as urine.

DNA: Deoxyribonucleic acid. DNA is a spiraling, ladder-like (helical) molecule that is the carrier of the genetic code. Nucleic acids are the primary components of the chromosomes within the nuclei of cells. DNA is also found in mitochondria, the rod-like structures outside the nuclei of cells that function as a primary source of cellular energy.

Dopamine: A neurotransmitter that controls movement and balance and is essential to the proper functioning of the central nervous system (CNS). Dopamine assists in the effective transmission of electrochemical signals from one nerve cell (neuron) to another.

Dopamine agonist (DA): A drug that acts like dopamine. DAs combine with dopamine receptors to mimic dopamine actions. Such medications stimulate dopamine receptors and produce dopamine-like effects.

Dopamine autoreceptor: A type of dopamine receptor that acts like a thermostat, preventing excess dopamine release as levels rise.

Dopamine receptor: A molecule on a receiving nerve cell (neuron) that is sensitive (or receptive) to stimulation (arousal) by dopamine or a dopamine agonist. At least five types have been identified including D1, D2, D3 receptors and the dopamine autoreceptor.

Dopamine receptor antagonist: A pharmacologic agent that binds to and blocks the action of dopamine receptors, essentially hindering receptor activity by preventing stimulation by dopamine.

Dopaminergic dysfunction: Malfunction of dopamine receptors.

Dysarthria: Disruption in speech. Disordered or impaired articulation of speech due to disturbances of muscular control, usually resulting from damage to the central or peripheral nervous system. Dysarthria is associated with certain neurodegenerative disorders, such as Parkinson's disease or Huntington's disease; cerebral palsy; brain tumors or stroke; or certain types of brain surgery.

Dysarthrophonia: speech dysfunction that affects respiration, phonation, articulation and prosody of speech.

Dysautonomia: Any disease or malfunction of the autonomic nervous system (system that we cannot consciously control. Such as heart rate, breathing, sweating, salivation, etc.). Common symptoms of dysautonomia would include orthostatic hypotension (feeling lightheaded if one rises from a chair to quickly), hypertension, or impotence.

Dysesthesias: Unpleasant sensations that are produced in response to normal stimuli.

Dyskinesias: Abnormal neuromuscular conditions characterized by disorganized or excessive movement (also known as hyperkinesia). Forms of dyskinesia include sudden, brief, "shock-like" muscle contractions (myoclonus); involuntary, rhythmic, oscillatory movements of a body part (tremor); rapid involuntary jerky movements (chorea); relatively slow writhing motions (athetosis); or abrupt, purposeless, simple or complex muscle movements or vocalizations (motor or vocal tics).

Dyskinesias while awake (DWA): Uncontrolled, sporadic movements of the legs and, in some cases, the arms. These movements may be very rapid (myoclonic) or quite slow and prolonged (dystonic); they usually disappear upon voluntary action. Some researchers suspect that these movements may represent a wakeful form of periodic limb movements in sleep (PLMS).

Dyspepsia:  Indigestion or upset stomach.

Dysphagia: Difficulty in swallowing. Dysphagia may be associated with esophageal obstruction as well as certain neurodegenerative or motor disorders involving the esophagus.

Dyspraxia: Partial loss of the ability to coordinate and perform certain purposeful movements and gestures in the absence of motor or sensory impairments.

Dystonia: 1. A state of abnormal (either hypo – little movement- or hyper – excessive movement) tonicity in any of the tissues resulting in impairment of voluntary movement. 2. A neurologic movement disorder characterized by sustained muscle contractions, resulting in repetitive, involuntary, twisting or writhing movements and unusual postures or positioning. Dystonia may be limited to specific muscle groups (focal dystonia), such as dystonia affecting muscles of the neck (cervical dystonia or spasmodic torticollis) or the eyes, resulting in closure of the eyelids (blepharospasm). 3. Dystonia is associated with certain underlying genetic disorders, such as dystonia musculorum deformans, dopa-responsive dystonia, and paroxysmal kinesigenic and paroxysmal non-kinesigenic dystonic choreoathetosis. The condition may result from the use of certain medications, lack of oxygen during or immediately after birth, or other causes of brain trauma.

Dystonic: Referring to dystonia; sudden jerky or repetitive movements and muscle spasms due to impaired muscle tone and abnormal muscle rigidity.

Dystopia: Malposition is a faulty, wrong, or abnormal position or placement of a body part or organ.

Echoacousia: a disturbance in someone's hearing in which a sound appears to be repeated.

Echolalia: when someone repeats the speech of somebody else in an involuntary and meaningless way. People with echolalia may repeat a word, phrase, or entire sentences.

Edema: An accumulation of an excessive amount of watery fluid in cells or intercellular tissues.

Effector organs: Organs that produce a nerve-stimulated effect, such as a muscle contraction or glandular secretion.

Electrical stimulation (ES): A test in which a small electrical charge is applied to a muscle via a needle to determine the level of muscle responsiveness.

Electrocardiogram (ECG, EKG): A noninvasive, diagnostic test that assesses the electrical activity of the heart muscle (myocardium). The heart's conduction system transmits electrical impulses that serve to coordinate contractions of the heart. During an ECG, the electrical activity of the cardiac conduction system is translated into recordings that assist in evaluating any abnormal alterations. The test may be administered while a patient is at rest or performing certain designated exercises. ECGs may help to detect or characterize cardiac conduction defects, abnormal heart rhythms (arrhythmias), enlargement (cardiac hypertrophy), or localized damage in heart muscle.

Electroencephalography (EEG): A noninvasive, diagnostic technique that records the electrical impulses produced by brain cell activity. An EEG reveals characteristic brain wave patterns that may assist in the diagnosis of particular neurologic conditions, such as seizure disorders, impaired consciousness, and brain lesions or tumors.

Electromyography (EMG): A diagnostic test that records the electrical responses of skeletal muscles while at rest and during voluntary action and electrical stimulation. During this test, a small needle is inserted into a muscle to record the level of activity.

Electrophysiologic studies: The study of the electrical activity associated with a specific body function (e.g., EMG, EEG, etc.).

Encephalalgia: is the same thing as headache.

Encephalitis: Inflammation of the brain. Encephalitis is most commonly caused by certain viral infections or may occur subsequent to prior infection due to immune reactions that indirectly result in inflammation (postinfectious encephalitis). Although associated symptoms and findings may be variable, features may include fever, headache, irritability, listlessness (lethargy), and weakness. Some affected individuals may also develop confusion, disturbances of speech and memory, abnormal involuntary movements, paralysis of one side of the body, seizures, and/or coma. For those with involvement of the protective membranes enclosing the brain and spinal cord (meningitis), characteristic findings may include nausea, vomiting, stiffness of the neck, abnormal sensitivity to light (photophobia), and/or other symptoms.

Encephalopathy: any disease or disorder of the structure or function of the brain, especially those that are destructive, worsening, or chronic.

Endogenous opiate system: Endorphins - a morphine-like substance that is produced within the body.

Enzyme: A protein produced by cells that accelerates the rate of or "catalyzes" a specific chemical reaction in the body without being consumed or permanently changed in the process. A chemical substance that is acted upon by an enzyme is called a "substrate." In many cases, enzymes are named by adding the suffix "-ase" to the name of the substrate upon which the enzyme exerts its action.

Epidemiological study: examination of the distribution of disease as well as the determining factors related to specific diseases or health-related problems in a specific population.

Ergot-derived medication: A medication that has a chemical structure based on ergot, a plant alkaloid produced by a fungus called Claviceps purpurea. Permax® and Parlodel® are examples of ergot-derived medications that may be used to treat certain neurologic movement disorders.

Erythematosus inflamed skin: redness of the skin.

Erythromelalgia: intermittent burning and throbbing in the extremities.

Esophageal atony: Lack of normal muscle tone within the esophagus, the muscular tube that transports food from the throat to the stomach.

Essential tremor (ET): A common, slowly and variably progressive neurologic movement disorder characterized by involuntary, rhythmic, "back and forth" movements (i.e., tremor) of a body part or parts. In ET patients, tremor is primarily a "postural" or "kinetic" tremor or may be a combination of both types: i.e., tremor occurs while voluntarily maintaining a fixed position against gravity (postural tremor) and/or when conducting self-directed, targeted actions (kinetic intention tremor). In many individuals with ET, both hands are affected, although the condition may sometimes initially be noted in the dominant hand. ET also frequently affects the head, with tremor occurring in a "no-no" horizontal pattern in about three quarters of patients and the remainder affected by vertical "yes-yes" tremors. Less commonly, patients have tremor involving the voice, tongue, or roof of the mouth (palate), leading to impaired articulation of speech (dysarthria). Rarely, tremor may affect the trunk or lower limbs, particularly with advanced stages of disease. ET may appear to occur randomly for unknown reasons (sporadically) or be transmitted as an autosomal dominant trait.

Estrogen: 1. Any of several, naturally occurring female sex hormones that promote the development of female secondary sexual characteristics and the proper functioning of the reproductive system; 2. synthetically produced agents used in birth control pills (oral contraceptives) or in the treatment of symptoms of menopause; osteoporosis, which is a bone disorder characterized by a progressive loss of bone mass; particular types of advanced postmenopausal breast cancer and prostate cancer; and other conditions.

Exacerbation: an increase in the seriousness of a disease or any of its signs and symptoms.

Exogenous: 1. Outside of the body. 2. Produced or beginning outside of an organism or outside one of the organism's parts. Some infections are described as exogenous if they arise from causes outside the body.

Extrapyramidal system: Refers to central nervous system structures (i.e., outside the cerebrospinal pyramidal tracts) that play a role in controlling motor functions. The extrapyramidal system includes substructures of the basal ganglia and the brainstem and interconnections with certain regions of the cerebellum, cerebrum, and other areas of the central nervous system. Extrapyramidal disturbances may result in postural and muscle tone abnormalities as well as the development of certain involuntary movements.

Eyelid-opening apraxia: Difficulty opening the eyelid.

Fecal softener: the same thing as stool softener.

Fibrosis: abnormal formation of tissue.

FIM: is an abbreviation for Functional Independence Measure. Functional Independence Measure refers to a scale that is used to measure one's ability to function with independence.

Flaccid: being weak, relaxed, soft, and flabby. When muscles are flaccid, it means that their normal tone (tension) is decreased. Thus, the muscles will appear weak, relaxed, soft, and flabby. A flaccid state can be caused by a prolonged loss of breathing, so that oxygen is not brought into the body and carbon dioxide is not brought out of the body.

Festination: involontary shortening of stride and quickening of gait that occurs in some diseases (e.g., Parkinson’s disease). It is most commonly used to describe gait disturbance, but it is also used to describe speech. For example, ones expression of words can accelerate while talking, and the space between words will become shorter and shorter. This happens to such a degree that it can be difficult to understand the individual who has festinating speech.

Flexion: The act of bending (as opposed to extending) a joint.

Fovea: A part of the eye. The fovea is responsible for sharp central vision, which is necessary in humans for reading, watching television or movies, driving, and any activity where visual detail is of primary importance.

Free radicals: Unstable molecular fragments that can damage cells. One hypothesis holds that free radical formation in the substantia nigra causes the loss of nigral cells (leading to Parkinson's disease).

Frequency: number of cycles or repetitions within a fixed unit of time such as the number of cycles per second (Hertz or Hz). For example, essential tremor is typically 4 to 12 Hz.

Friedreich's ataxia: Friedreich's ataxia is the most common autosomal recessively inherited type of ataxia. Like the autosomal dominant spinocerebellar ataxias, the main symptoms are loss of coordination and unsteadiness of gait. Other systems may also be affected and people with Friedreich's ataxia should be monitored for heart disease and diabetes. The affected protein is called frataxin, and is thought to be involved in iron metabolism.

Froment's sign: Increased resistance to passive movements of a limb that may be detected upon voluntary activity of another body part.

Functional Independence Measure: a scale that is used to measure one's ability to function with independence.

Functional Magnetic Resonance Imaging (fMRI): A noninvasive, diagnostic scanning procedure that produces detailed, computerized images. The use of a "contrast agent" or dye enhances the detail of the images. Sequencing of these images may help physicians visualize the body's functioning, thus aiding differential diagnosis.

Ganglion cell: A type of neuron located in the retina of the eye that receives visual information.

Gait: The style or manner of walking. Gait disturbances may be associated with certain neurologic or neuromuscular disorders, orthopedic conditions, inflammatory conditions of the joints (i.e., arthritic changes), or other abnormalities.

Gait apraxia: Loss of the ability to consciously sequence and execute the movements required to coordinate walking. Gait apraxia may result in unsteady walking patterns; "toe-walking"; a widely based, jerky gait; and balance difficulties.

Gamma knife radiosurgery: a highly specialized technique using a device that produces ionizing radiation to produce a lesion in the target tissue. This device focuses a beam of high intensity irradiation to a targeted area and is used as localized therapy to treat individuals with certain brain diseases (e.g., brain tumors, certain movement disorders, etc.).

Gamma-aminobutyric acid (GABA): a chemical messenger in the brain, spinal cord, heart, lungs, and kidneys, which sends messages telling the body to slow down. GABA is the primary inhibitory neurotransmitter in the brain.

Gastroesophageal reflux: Backflow of stomach contents into the esophagus. This condition may be chronic and cause weakness of the lower esophageal sphincter, the ring-shaped muscle located at the junction of the esophagus and stomach.

Gastroparesis:  Slowed or delayed movement of food through the stomach into the small intestine due to damage to the vagus nerve (cranial nerve) which causes paralysis of the stomach muscles.  There are many diseases, including PD that can cause this condition while many times the cause is unknown.  Symptoms may include heartburn, difficult to control blood glucose levels, nausea, bloating, decreased appetite, etc.

Gastrostomy tube: A plastic tube inserted into the stomach through a surgical incision in the abdomen. A gastrostomy tube is used to deliver liquified food to the digestive system when swallowing becomes dangerous or difficult.

Genetic anticipation: A phenomenon in which the onset of symptoms of a hereditary disease appears to occur at a progressively earlier age in successive generations. Genetic anticipation has been demonstrated in a number of hereditary disorders (such as Huntington's disease, dentatorubropallidoluysian atrophy, etc.) in which the gene mutation consists of abnormally long sequences or "repeats" of particular coded instructions (e.g., unstable expansion of CAG repeats). With other disorders in which genetic anticipation has previously been suggested (e.g., essential tremor), studies have indicated that increased awareness of the condition in affected families may be responsible for earlier recognition of symptom onset.

Genetic heterogeneity: Manifestation of similar or the same observable characteristics or traits (i.e., phenotype) resulting from different genetic mechanisms, such as changes (mutations) of different genes or a combination of genes.

Genitourinary:  Referring to the bladder and genital areas.

Germline mosaicism: The presence of a gene mutation for a disease trait in some yet not all of an individual's sexual reproductive cells (germ cells) within the ovaries or testes (gonads). Germline mosaicism is sometimes suspected when parents have more than one child with a genetic disorder transmitted as a dominant trait yet neither parent appears to be affected by the condition.

Gliosis: A proliferation of astrocytes in damaged areas of the central nervous system (CNS). Astrocytes are relatively large glial cells, which are the connective tissue cells of the CNS. Astrocytes have various functions, including accumulating in areas where nerve cells (neurons) have been damaged. Gliosis and neuronal loss in certain brain regions are findings seen in various neurodegenerative disorders.

Globus pallidus: A major substructure of the basal ganglia deep within the brain. Specialized groups of nerve cells in the globus pallidus function as an "intermediate relay system." This system processes and transmits information from the basal ganglia by way of the thalamus to areas of the brain that regulate complex motor functions (e.g., motor cortex, premotor area of frontal lobe).

Glottis: 1. The slit-like opening between the vocal cords; the region of the voice box (larynx) consisting of the vocal cords and the opening between them. 2. Thin strips of muscle inside the throat that produce sound by moving slightly as air travels over them.

Glutamate: An amino acid that is a primary excitatory neurotransmitter in the central nervous system. This chemical agent plays an essential role in initiating and transmitting nerve impulses, crossing synapses to stimulate postsynaptic neurons.

Gray matter: Nerve tissue that primarily consists of nerve cell bodies, dendrites, and unmyelinated axons, thus having a gray appearance. In contrast, white matter predominantly contains myelinated nerve fibers.

Hallervorden-Spatz disease: A slowly progressive hereditary disorder characterized by abnormal accumulations of iron pigments in certain regions of the basal ganglia (e.g., globus pallidus and substantia nigra). This autosomal recessive disorder typically becomes apparent during late childhood or adolescence. Associated symptoms may include progressive stiffness and resistance to movement (rigidity); increasing difficulties speaking and eating; sustained muscle contractions that result in repetitive twisting motions or unusual postures or positions (dystonia); the presence of multiple, irregular, jerky motions that may combine to appear flowing or writhing in nature (choreoathetosis); and/or other abnormalities.

Hallucinations: The apparent, often strong subjective perception of an object or event when no such stimulus or situation is present; may be visual, auditory, olfactory, gustatory, or tactile. Perceptions that occur in the absence of external stimuli and while an individual is awake. Hallucinations may occur with high-dose administration of certain medications or the abuse of particular drugs (hallucinogens) that cause increased stimulation or excitation of the central nervous system. They may also be caused by chronic alcohol abuse; sensory deprivation; certain types of seizures due to impairment or damage of a limited area of the brain (e.g., temporal lobe epilepsy); psychotic illnesses characterized by disturbances in thought, behavior, and emotional reactions (schizophrenia); or certain organic disorders, such as Huntington's disease.

Hemiballismus: Throwing of the limbs to one side of the body.

Hemichorea: Irregular, abrupt, relatively rapid involuntary (i.e., choreic) movements that are unilateral or involve muscle groups on one side of the body.

Hemihyperhidrosis: excessive sweating on one side of the body. This condition is known to occur in some patients who have experienced a stroke. A stroke is a burst artery (a type of blood vessel that carries blood away from the heart) or a blockage of an artery in the brain. Strokes in an area of the lower part of the brain known as the medulla have been associated with increased sweating on the side of the body that is opposite of the side that the stroke occurred in the brain.

Hemizygote: Refers to a cell, organism, or individual with only one of a pair of genes for a specific trait. This term is often used to describe males who inherit one copy of an X-linked disease trait. It may also refer to the state in which genetic material is deleted from one member of a chromosomal pair.

Hereditary: Inherited; inborn; referring to the genetic transmission of a trait, condition, or disorder from parent to offspring.

Heredodegenerative: Pertaining to genetically transmitted (hereditary) neurologic disorders characterized by progressive neuronal loss and other neurodegenerative changes (e.g., associated gliosis). For example, the term "heredodegenerative dystonias" is used to refer to several, usually hereditary disorders in which neurodegenerative changes may lead to dystonia as a primary feature and other neurologic symptoms are typically present. However, in some patients with such disorders, dystonia may not always develop and other neurologic features may be primary findings. Disorders that have been categorized as heredodegenerative dystonias include ataxia-telangiectasia, Hallervorden-Spatz disease, Huntington's disease, Parkinson's disease, progressive supranuclear palsy, neuroacanthocytosis, and Wilson's disease.

Hertz (Hz): cycles per second.

Heterozygous carriers: The term "heterozygosity" refers to the state of having different genes that occupy the same position (locus) on one or more paired chromosomes. "Heterozygous carriers" describes individuals who carry a single copy of a mutated gene for a disease trait, such as females who have a copy of a disease gene for an X-linked disorder. Because females have two X chromosomes yet only one functioning copy is necessary, a percentage of X chromosomes with the mutated gene may not be expressed, typically in a random pattern (known as "random X chromosome inactivation"). Therefore, females who are heterozygous for an X-linked disease trait often have no disease manifestations or less severe symptoms than affected males. However, because males have one X chromosome from the mother and one Y chromosome from the father, males who carry an X-linked disease trait will typically fully express the mutated gene. Rarely, females who are heterozygous for an X-linked disease trait may manifest symptoms with about the same severity as affected males.

Hidrosis: is the production and release of sweat.

Homeostasis: Internal stabilization or equilibrium of a living organism (e.g. person) in order for the person to live and function properly.

Homocystinuria: A metabolic abnormality characterized by excessive amounts of the amino acid homocystine in the urine. Homocystinuria, which may be transmitted as an autosomal recessive trait, may result from deficient activity of certain enzymes involved in the metabolic conversion of the amino acid methionine to cysteine. Associated symptoms and findings often include developmental delay; dislocated lens of the eyes (ectopia lentis); thin, weak muscles; progressive mental retardation; psychiatric abnormalities; skeletal defects; blockage of a blood vessel by a piece of a blood clot (thrombus) carried in the bloodstream (thromboembolism); and/or other abnormalities.

Huntington's disease (HD): A hereditary, progressive, neurodegenerative disorder primarily characterized by the development of emotional, behavioral, and psychiatric abnormalities; gradual deterioration of thought processing and acquired intellectual abilities (dementia); and movement abnormalities, including involuntary, rapid, irregular jerky movements (chorea) of the face, arms, legs, or trunk. HD may be inherited as an autosomal dominant trait or, less commonly, appear to occur randomly for unknown reasons (sporadically). The disorder results from abnormally long sequences or "repeats" of certain coded instructions (i.e., unstable expanded CAG repeats) within a gene (located on chromosome p16.3). Progressive nervous system dysfunction associated with HD results from loss of neurons in certain areas of the brain, including the basal ganglia and cerebral cortex.

Hyperglycemia: An abnormally high level of the simple sugar glucose in the blood.

Hyperhidrosis: Excessive sweating

Hyperkalemic: Pertaining to hyperkalemia, a condition characterized by unusually high concentrations of potassium in the blood. Potassium, a positively charged ion, helps to regulate water balance, nerve conduction, and muscle contraction. Hyperkalemia may lead to various signs and symptoms, such as diarrhea, nausea, abdominal cramps, weakness, and, with increasing severity, abnormal heart rhythms and muscle paralysis.

Hyperkinetic: Characterized by excessive movement because of abnormally increased motor activity or function. Certain movement disorders are termed "hyperkinetic" such as tics or essential tremor.

Hyperventilation: Abnormally rapid breathing usually accompanied by air swallowing. Hyperventilation results in excessive intake of oxygen and increased elimination of carbon dioxide, which may eventually lead to a disturbance in the body's acid-base balance.

Hypokalemic: Referring to hypokalemia, which is characterized by abnormally low potassium levels in the blood. Potassium, the primary positively charged ion (cation) of muscle, plays an important role in regulating muscle contraction, nerve conduction, and other bodily functions. Hypokalemia may result in confusion, fatigue, weakness, and, in severe cases, paralysis and heart rhythm abnormalities.

Hypokinetic: Diminished movement and decreased motor function. Some movement disorders are hypokinetic, such as Parkinson's disease.

Hypokinetic Dysarthria:  A disorder of speech that may be described as monotonous, breathy, and harsh mixed with hesitations as well as a variable rate of speech.  This type of speech disorder is commonly seen in PD.  The etiology of the disorder is associated with the basal ganglia, specifically the substantia nigra.

Hypoparathyroidism: An endocrine condition characterized by insufficient secretion of parathyroid hormone due to injury, disease, or congenital abnormalities of the parathyroid glands. Parathyroid hormone plays an essential role in regulating calcium balance in the body. Hypoparathyroidism results in low calcium blood levels (hypocalcemia), leading to various symptoms and findings. For example, hypoparathyroidism may cause a condition known as tetany in which increased excitability of nerves and muscles results in uncontrollable, painful muscle spasms and cramping; abnormal involuntary movements resembling chorea; spasmodic closure of the larynx (laryngospasm); and other findings. Hypoparathyroidism may also lead to seizures; abnormal calcium deposits (calcifications) in the basal ganglia; loss of transparency of the lenses of the eyes (cataracts); dry, scaly skin; weakened tooth enamel; and/or other abnormalities.

Hypophonia: a disturbance in speech which is characterized by softening in volume – low volume.