Neurological Conditions

Definitions - Neurological Conditions - L

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

Lambert-Eaton Myasthenic Syndrome - (LEMS) is a rare disorder of neuromuscular transmission. It is a presynaptic disorder of neuromuscular transmission in which quantal release of acetylcholine (ACh) is impaired,  causing a unique set of clinical characteristics, which include proximal muscle weakness, depressed tendon reflexes, posttetanic potentiation, and autonomic changes. The initial presentation can be similar to that of  myasthenia gravis, but the progressions of the two diseases have some important differences.

Landau-Kleffner Syndrome - (LKS) is a rare, childhood neurological disorder characterized by the sudden or gradual development of aphasia (the inability to understand or express language) and an abnormal  electro-encephalogram (EEG). LKS affects the parts of the brain that control comprehension and speech. The disorder usually occurs in children between the ages of 5 and 7 years. Typically, children with LKS  develop normally but then lose their language skills for no apparent reason.

Lateral Medullary Syndrome - (also called Wallenberg's syndrome and posterior inferior cerebellar artery syndrome) is a disease in which the patient has difficulty with swallowing or speaking or both owing to one or  more patches of dead tissue (known as an infarct) caused by interrupted blood supply to parts of the brain.

Learning Disabilities - disorders that affect the ability to understand or use spoken or written language, do mathematical calculations, coordinate movements, or direct attention. Although learning disabilities occur in  very young children, the disorders are usually not recognized until the child reaches school age.

Leigh's Disease - form of Leigh syndrome, also known as Subacute Necrotizing Encephalomyelopathy (SNEM), an inherited disorder which usually affects infants, but in rare cases, teenagers and adults, as well. In  the case of the disease, mutations in mitochondrial DNA or in nuclear DNA (gene SURF1 and some COX assembly factors) cause degradation of motor skills and eventually death.

Lennox-Gastaut Syndrome - a severe form of epilepsy. Seizures usually begin before 4 years of age. Seizure types, which vary among patients, include tonic (stiffening of the body, upward deviation of the eyes,  dilation of the pupils, and altered respiratory patterns), atonic (brief loss of muscle tone and consciousness, causing abrupt falls), atypical absence (staring spells), and myoclonic (sudden muscle jerks).

Lesch-Nyhan Syndrome - also known as Nyhan’s syndrome, is a rare, inherited disorder caused by a deficiency of the enzyme hypoxanthine-guanine phosphoribosyltransferase (HGPRT). LNS is an X-linked recessive  disease: the gene is carried by the mother and passed on to her son. LNS is present at birth in baby boys. Patients have severe mental and physical problems throughout life.

Leukodystrophy - refers to progressive degeneration of the white matter of the brain due to imperfect growth or development of the myelin sheath, the fatty covering that acts as an insulator around nerve fiber. Myelin,  which lends its color to the white matter of the brain, is a complex substance made up of at least ten different chemicals. The leukodystrophies are a group of disorders that are caused by genetic defects in how  myelin produces or metabolizes these chemicals.

Levine-Critchley Syndrome - very rare inherited disorder mainly involving progressive muscle weakness and wasting, abnormal limb movement, progressive cognitive loss and red blood cell abnormalities.

Lewy Body Dementia - one of the most common types of progressive dementia. The central feature of DLB is progressive cognitive decline, combined with three additional defining features:  (1) pronounced  “fluctuations” in alertness and attention, such as frequent drowsiness, lethargy, lengthy periods of time spent staring into space, or disorganized speech; (2) recurrent visual hallucinations,  and (3) parkinsonian motor  symptoms, such as rigidity and the loss of spontaneous movement.

Lipid Storage Diseases - or the lipidoses, are a group of inherited metabolic disorders in which harmful amounts of fatty materials called lipids accumulate in some of the body’s cells and tissues.  People with these  disorders either do not produce enough of one of the enzymes needed to metabolize lipids or they produce enzymes that do not work properly.  Over time, this excessive storage of fats can cause permanent cellular  and tissue damage, particularly in the brain, peripheral nervous system, liver, spleen, and bone marrow.

Lipoid Proteinosis - rare autosomal recessive genodermatosis characterized by the deposition of an amorphous hyaline material in the skin, mucosa, and viscera. The classic manifestation is onset in infancy with a  hoarse cry due to laryngeal infiltration. Skin and mucous membrane changes become apparent clinically, and the disease typically follows a slowly progressive, yet often benign, course.

Lissencephaly - a rare brain formation disorder characterized by the lack of normal convolutions (folds) in the brain. It is caused by defective neuronal migration, the process in which nerve cells move from their place  of origin to their permanent location. It is a form of cephalic disorder.

Locked-In Syndrome - is a condition in which a patient is aware and awake, but cannot move or communicate due to complete paralysis of nearly all voluntary muscles in the body. It is the result of a brain stem lesion  in which the ventral part of the pons is damaged.

Lou Gehrig's Disease - or Amyotrophic lateral sclerosis (ALS), a rapidly progressive, invariably fatal neurological disease that attacks the nerve cells (neurons) responsible for controlling voluntary muscles.  In ALS,  both the upper motor neurons and the lower motor neurons degenerate or die, ceasing to send messages to muscles. Unable to function, the muscles gradually weaken, waste away, and twitch. Eventually the ability  of the brain to start and control voluntary movement is lost. Lou Gehrig's Disease Symptoms - Individuals with ALS lose their strength and the ability to move their arms, legs, and body. When muscles in the diaphragm and chest wall fail, individuals  lose the ability to breathe without ventilatory support.

Lupus - Neurological Sequelae - (also called systemic lupus erythematosus) is a disorder of the immune system. Normally, the immune system protects the body against invading infections and cancers. In lupus, the  immune system is over-active and produces increased amounts of abnormal antibodies that attack the body's tissues and organs. Lupus can affect many parts of the body, including the joints, skin, kidneys, lungs,  heart, nervous system, and blood vessels. The signs and symptoms of lupus differ from person to person; the disease can range from mild to life threatening.

Lyme Disease - Neurological Complications - Lyme disease is caused by a bacterial organism that is transmitted to humans via the bite of an infected tick. Most people bitten by an infected tick develop a  characteristic skin rash around the area of the bite. The rash may feel hot to the touch, and vary in size, shape, and color, but it will often have a "bull's eye" appearance (a red ring with a clear center). However, there  are those who will not develop the rash, which makes Lyme disease hard to diagnose because its symptoms and signs mimic those of many other diseases.

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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