Neurological Conditions

Definitions - Neurological Conditions - M - Machado-Joseph Disease to Myotonia

Neurological Conditions Definitions. These definitions from Disabled World begin with the letter G.

Machado-Joseph Disease - (MJD)-also called spinocerebellar ataxia type 3-is a rare hereditary ataxia. (Ataxia is a general term meaning lack of muscle control.) The disease is characterized by clumsiness and weakness in the arms and legs, spasticity, a staggering lurching gait easily mistaken for drunkenness, difficulty with speech and swallowing, involuntary eye movements, double vision, and frequent urination. Some patients have dystonia (sustained muscle contractions that cause twisting of the body and limbs, repetitive movements, abnormal postures, and/or rigidity) or symptoms similar to those of Parkinson's disease. Others have twitching of the face or tongue, or peculiar bulging eyes.

Macrencephaly - also called macrencephaly, is a condition in which an infant or child has an abnormally large, heavy, and usually malfunctioning brain. By definition, the brain weight is greater than average for the age and gender of the child. Head enlargement may be evident at birth or the head may become abnormally large in the early years of life. Megalencephaly is thought to be related to a disturbance in the regulation of cell production in the brain. In normal development, neuron proliferation - the process in which nerve cells divide to form new generations of cells - is regulated so that the correct number of cells is produced in the proper place at the appropriate time. In a megalencephalic brain, too many cells are produced either during development or progressively as part of another disorder, such as one of the neurofibromatoses or leukodystrophies. Symptoms of megalencephaly include delayed development, seizures, and corticospinal (brain cortex and spinal cord) dysfunction. Megalencephaly affects males more often than females. Unilateral megalencephaly or hemimegalencephaly is a rare condition that is characterized by the enlargement of one side of the brain. Children with this disorder may have a large, asymmetrical head accompanied by seizures, partial paralysis, and mental retardation.

Melkersson-Rosenthal Syndrome - is a rare neurological disorder characterized by recurring facial paralysis, swelling of the face and lips (usually the upper lip), and the development of folds and furrows in the tongue. Onset is in childhood or early adolescence. After recurrent attacks (ranging from days to years in between), swelling may persist and increase, eventually becoming permanent. The lip may become hard, cracked, and fissured with a reddish-brown discoloration. The cause of Melkersson-Rosenthal syndrome is unknown, but there may be a genetic predisposition. It can be symptomatic of Crohn's disease or sarcoidosis.

Meningitis - is the inflammation of the protective membranes covering the central nervous system, known collectively as the meninges. Meningitis may develop in response to a number of causes, most prominently bacteria, viruses and other infectious agents, but also physical injury, cancer, or certain drugs. While some forms of meningitis are mild and resolve on their own, meningitis is a potentially serious condition owing to the proximity of the inflammation to the brain and spinal cord. The potential for serious neurological damage or even death necessitates prompt medical attention and evaluation.

Menkes Disease - is caused by a defective gene that regulates the metabolism of copper in the body. Because it is an X-linked gene, the disease primarily affects male infants. Copper accumulates at abnormally low levels in the liver and brain, but at higher than normal levels in the kidney and intestinal lining. Affected infants may be born prematurely. Symptoms appear during infancy. Normal or slightly slowed development may proceed for 2 to 3 months, and then there will be severe developmental delay and a loss of early developmental skills. Menkes Disease is also characterized by seizures, failure to thrive, subnormal body temperature, and strikingly peculiar hair, which is kinky, colorless or steel-colored, and easily broken. There can be extensive neurodegeneration in the gray matter of the brain. Arteries in the brain can also be twisted with frayed and split inner walls. This can lead to rupture or blockage of the arteries. Weakened bones (osteoporosis) may result in fractures.

Meralgia Paresthetica - is a disorder characterized by tingling, numbness, and burning pain in the outer side of the thigh. The disorder is caused by compression of the lateral femoral cutaneous nerve as it exits the pelvis. It more commonly occurs in men than women, and is generally found in middle-aged or overweight individuals. People with the disorder frequently report that it appears or worsens after walking or standing. The skin is often sensitive to touch. Meralgia paresthetica is associated with clothing that is too tight, pregnancy, diabetes, and obesity.

Metachromatic Leukodystrophy - (MLD, also called Arylsulfatase A deficiency) is the most common form of a family of genetic diseases known as the leukodystrophies, diseases which affect the growth and/or development of myelin, the fatty covering which acts as an insulator around nerve fibers throughout the central and peripherial nervous systems .

Microcephaly - is a medical condition in which the circumference of the head is smaller than normal because the brain has not developed properly or has stopped growing. Microcephaly can be present at birth or it may develop in the first few years of life. It is most often caused by genetic abnormalities that interfere with the growth of the cerebral cortex during the early months of fetal development. It is associated with Down’s syndrome, chromosomal syndromes, and neurometabolic syndromes. Babies may also be born with microcephaly if, during pregnancy, their mother abused drugs or alcohol, became infected with a cytomegalovirus, rubella (German measles), or varicella (chicken pox) virus, was exposed to certain toxic chemicals, or had untreated phenylketonuria (PKU). Babies born with microcephaly will have a smaller than normal head that will fail to grow as they progress through infancy. Depending on the severity of the accompanying syndrome, children with microcephaly may have mental retardation, delayed motor functions and speech, facial distortions, dwarfism or short stature, hyperactivity, seizures, difficulties with coordination and balance, and other brain or neurological abnormalities.

Migraine - The pain of a migraine headache is often described as an intense pulsing or throbbing pain in one area of the head. It is often accompanied by extreme sensitivity to light and sound, nausea, and vomiting. Migraine is three times more common in women than in men. Some individuals can predict the onset of a migraine because it is preceded by an "aura," visual disturbances that appear as flashing lights, zig-zag lines or a temporary loss of vision. People with migraine tend to have recurring attacks triggered by a lack of food or sleep, exposure to light, or hormonal irregularities (only in women). Anxiety, stress, or relaxation after stress can also be triggers. For many years, scientists believed that migraines were linked to the dilation and constriction of blood vessels in the head. Investigators now believe that migraine is caused by inherited abnormalities in genes that control the activities of certain cell populations in the brain.

Miller Fisher Syndrome - is a rare, acquired nerve disease that is considered to be a variant of Guillain-Barré syndrome. It is characterized by abnormal muscle coordination, paralysis of the eye muscles, and absence of the tendon reflexes. Like Guillain-Barré syndrome, symptoms may be preceded by a viral illness. Additional symptoms include generalized muscle weakness and respiratory failure. The majority of individuals with Miller Fisher syndrome have a unique antibody that characterizes the disorder.

Mini-Strokes - A transient ischemic attack (TIA) is a transient stroke that lasts only a few minutes. It occurs when the blood supply to part of the brain is briefly interrupted. TIA symptoms, which usually occur suddenly, are similar to those of stroke but do not last as long. Most symptoms of a TIA disappear within an hour, although they may persist for up to 24 hours. Symptoms can include: numbness or weakness in the face, arm, or leg, especially on one side of the body; confusion or difficulty in talking or understanding speech; trouble seeing in one or both eyes; and difficulty with walking, dizziness, or loss of balance and coordination.

Mitochondrial Myopathies - are a group of neuromuscular diseases caused by damage to the mitochondria—small, energy-producing structures that serve as the cells' "power plants." Nerve cells in the brain and muscles require a great deal of energy, and thus appear to be particularly damaged when mitochondrial dysfunction occurs. Some of the more common mitochondrial myopathies include Kearns-Sayre syndrome, myoclonus epilepsy with ragged-red fibers, and mitochondrial encephalomyopathy with lactic acidosis and stroke-like episodes. The symptoms of mitochondrial myopathies include muscle weakness or exercise intolerance, heart failure or rhythm disturbances, dementia, movement disorders, stroke-like episodes, deafness, blindness, droopy eyelids, limited mobility of the eyes, vomiting, and seizures. The prognosis for these disorders ranges in severity from progressive weakness to death. Most mitochondrial myopathies occur before the age of 20, and often begin with exercise intolerance or muscle weakness.

Motor Neuron Diseases - (MNDs) are a group of progressive neurological disorders that destroy motor neurons, the cells that control essential voluntary muscle activity such as speaking, walking, breathing, and swallowing. Normally, messages from nerve cells in the brain (called upper motor neurons) are transmitted to nerve cells in the brainstem and spinal cord (called lower motor neurons ) and from them to particular muscles. Upper motor neurons direct the lower motor neurons to produce movements such as walking or chewing. Lower motor neurons control movement in the arms, legs, chest, face, throat, and tongue.

Moyamoya Disease - is a rare, progressive cerebrovascular disorder caused by blocked arteries at the base of the brain in an area called the basal ganglia. The name “moyamoya” means “puff of smoke” in Japanese and describes the look of the tangle of tiny vessels formed to compensate for the blockage. Moyamoya disease was first described in Japan in the 1960’s and it has since been found in individuals in the United States , Europe, Australia , and Africa. The disease primarily affects children, but it can also occur in adults. In children, the first symptom of Moyamoya disease is often stroke, or recurrent transient ischemic attacks (TIA, commonly referred to as “mini-strokes”), frequently accompanied by muscular weakness or paralysis affecting one side of the body, or seizures. Adults most often experience a hemorrhagic stroke due to recurring blood clots in the affected brain vessels. Individuals with this disorder may have disturbed consciousness, speech deficits (usually aphasia), sensory and cognitive impairments, involuntary movements, and vision problems.

Mucolipidoses - The mucolipidoses (ML) are a group of inherited metabolic diseases that affect the body’s ability to carry out the normal turnover of various materials within cells. In ML, abnormal amounts of carbohydrates or fatty materials (lipids) accumulate in cells. Because our cells are not able to handle such large amounts of these substances, damage to the cells occurs, causing symptoms that range from mild learning disabilities to severe mental retardation and skeletal deformities.

Mucopolysaccharidoses - The mucopolysaccharidoses are a group of inherited metabolic diseases caused by the absence or malfunctioning of certain enzymes needed to break down molecules called glycosaminoglycans - long chains of sugar carbohydrates in each of our cells that help build bone, cartilage, tendons, corneas, skin, and connective tissue. Glycosaminoglycans (formerly called mucopolysaccharides) are also found in the fluid that lubricates our joints. People with a mucopolysaccharidosis either do not produce enough of one of the 11 enzymes required to break down these sugar chains into proteins and simpler molecules or they produce enzymes that do not work properly. Over time, these glycosaminoglycans collect in the cells, blood, and connective tissues. The result is permanent, progressive cellular damage that affects the individual's appearance, physical abilities, organ and system functioning, and, in most cases, mental development.

Multiple System Atrophy - with orthostatic hypotension is the current classification for a neurological disorder that was once called Shy-Drager syndrome. A progressive disorder of the central and autonomic nervous systems, it is characterized by orthostatic hypotension (an excessive drop in blood pressure when standing up) which causes dizziness or fainting. Multiple system atrophy can occur without orthostatic hypotension, but it is rare. Doctors classify the disorder into 3 types: the Parkinsonian-type includes symptoms of Parkinson's disease such as slow movement, stiff muscles, and tremor; the cerebellar-type, which causes problems with coordination and speech; and the combined-type, which includes symptoms of both parkinsonism and cerebellar failure. Problems with urinary incontinence, constipation, and sexual impotence in men happen early in the course of the disease. Other symptoms include generalized weakness, double vision or other vision disturbances, difficulty breathing and swallowing, sleep disturbances, and decreased sweating. Because the disease resembles others, a correct diagnosis may take years.

Muscular Dystrophy - The muscular dystrophies (MD) are a group of more than 30 genetic diseases characterized by progressive weakness and degeneration of the skeletal muscles that control movement. Some forms of MD are seen in infancy or childhood, while others may not appear until middle age or later. The disorders differ in terms of the distribution and extent of muscle weakness (some forms of MD also affect cardiac muscle), age of onset, rate of progression, and pattern of inheritance.Duchenne MD is the most common form of MD and primarily affects boys. It is caused by the absence of dystrophin, a protein involved in maintaining the integrity of muscle. Onset is between 3 and 5 years and the disorder progresses rapidly. Most boys are unable to walk by age 12, and later need a respirator to breathe. Girls in these families have a 50 percent chance of inheriting and passing the defective gene to their children. Boys with Becker MD (very similar to but less severe than Duchenne MD) have faulty or not enough dystrophin.Facioscapulohumeral MD usually begins in the teenage years. It causes progressive weakness in muscles of the face, arms, legs, and around the shoulders and chest. It progresses slowly and can vary in symptoms from mild to disabling.Myotonic MD is the disorder's most common adult form and is typified by prolonged muscle spasms, cataracts, cardiac abnormalities, and endocrine disturbances. Individuals with myotonic MD have long, thin faces, drooping eyelids, and a swan-like neck.

Myasthenia Gravis - is a chronic autoimmune neuromuscular disease characterized by varying degrees of weakness of the skeletal (voluntary) muscles of the body. The name myasthenia gravis, which is Latin and Greek in origin, literally means "grave muscle weakness." With current therapies, however, most cases of myasthenia gravis are not as "grave" as the name implies. In fact, for the majority of individuals with myasthenia gravis, life expectancy is not lessened by the disorder. The hallmark of myasthenia gravis is muscle weakness that increases during periods of activity and improves after periods of rest. Certain muscles such as those that control eye and eyelid movement, facial expression, chewing, talking, and swallowing are often, but not always, involved in the disorder. The muscles that control breathing and neck and limb movements may also be affected.

Myoclonus - describes a symptom and generally is not a diagnosis of a disease. It refers to sudden, involuntary jerking of a muscle or group of muscles. Myoclonic twitches or jerks usually are caused by sudden muscle contractions, called positive myoclonus, or by muscle relaxation, called negative myoclonus. Myoclonic jerks may occur alone or in sequence, in a pattern or without pattern. They may occur infrequently or many times each minute. Myoclonus sometimes occurs in response to an external event or when a person attempts to make a movement. The twitching cannot be controlled by the person experiencing it.

Myopathy - The myopathies are neuromuscular disorders in which the primary symptom is muscle weakness due to dysfunction of muscle fiber. Other symptoms of myopathy can include include muscle cramps, stiffness, and spasm. Myopathies can be inherited (such as the muscular dystrophies) or acquired (such as common muscle cramps).

Myopathies are grouped as follows:

congenital myopathies: characterized by developmental delays in motor skills; skeletal and facial abnormalities are occasionally evident at birth
muscular dystrophies: characterized by progressive weakness in voluntary muscles; sometimes evident at birth.

mitochondrial myopathies: caused by genetic abnormalities in mitochondria, cellular structures that control energy; include Kearns-Sayre syndrome, MELAS and MERRF.

glycogen storage diseases of muscle: caused by mutations in genes controlling enzymes that metabolize glycogen and glucose (blood sugar); include Pompe's, Andersen's and Cori's diseases.

myoglobinurias: caused by disorders in the metabolism of a fuel (myoglobin) necessary for muscle work; include McArdle, Tarui, and DiMauro diseases.

dermatomyositis: an inflammatory myopathy of skin and muscle
myositis ossificans: characterized by bone growing in muscle tissue.

familial periodic paralysis: characterized by episodes of weakness in the arms and legs.

polymyositis, inclusion body myositis, and related myopathies: inflammatory myopathies of skeletal muscle.

neuromyotonia: characterized by alternating episodes of twitching and stiffness.

stiff-man syndrome: characterized by episodes of rigidity and reflex spasms common muscle cramps and stiffness, and tetany: characterized by prolonged spasms of the arms and legs.

Myotonia - is an inherited neuromuscular disorder characterized by the inability of muscles to quickly relax after a voluntary contraction. The condition is present since early childhood, but symptoms can be mild. Most children will be 2 or 3 years old when parents first notice their muscle stiffness, particularly in the legs, often provoked by sudden activity after rest. The disease doesn’t cause muscle wasting; in fact, it may cause muscle enlargement. Muscle strength is increased. There are two forms of the disorder: Becker-type, which is the most common form; and Thomsen’s disease, which is a rare and milder form. The disorder is cause by mutations in a gene responsible for shutting off electrical excitation in the muscles.

Alphabetical list of Neurological Disorder Definitions.

A - B - C - D - E - F - G - H - I - J - K - L - M - N - O - P - R - S - T - V - W - X - Z

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