Category: L
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Leukodystrophy
A group of disorders characterized by progressive degeneration of the white matter of the brain, caused by genetic defects in the growth or development of myelin, the fatty covering that acts as an insulator around nerve fibers. Leukodystrophy refers to a group of progressive genetic disorders that affect the brain, spinal cord, and peripheral nerves.…
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Leukoaraiosis
A radiological finding of changes in the white matter in aged individuals that can be detected with high frequency by computed tomography (CT) and magnetic resonance imaging (MRI). This white matter pathology is inconsistently associated with cognitive impairment, motor dysfunction, and gait disturbances. Slowed cognitive processing and frontal executive abilities are also common. It may…
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Lethologica
Temporary inability to remember a proper noun or name.
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Lethality index
Set of criteria used to predict suicide.
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Lesch-nyhan syndrome
A rare, genetic neurological disorder characterized by self-mutilating behaviors such as head banging and/or lip and finger biting, uncontrolled spastic muscle movements, and involuntary movements of the upper extremities. Moderate intellectual disability is also common. A relatively rare genetic disease characterized by mental retardation and compulsive self-mutilation accompanied by uremia. A rare genetic disorder in boys…
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Lesbian
A female who is homosexual. A woman who experiences sexual attraction towards other women. A female homosexual; lesbians form about 2 per cent of the female population in the UK. Some engage in active sexual behaviour with another woman, with masturbation, mutual stimulation of the clitoris and oral sex being the usual techniques for achieving…
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Lentiform nucleus
The large, cone-shaped mass of gray matter that forms the central core of the cerebral hemisphere, whose convex base is formed by the putamen and whose apical part consists of the globus pallidus. Also called lenticular nucleus.
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Lennox-gastaut syndrome
A severe form of epilepsy with developmental delays and behavioral disturbances. Lennox-Gastaut syndrome (LGS) is a severe form of epilepsy. The syndrome consists of the following primary characteristics: multiple types of seizures (e.g., tonic, atonic, myoclonic, and atypical absence), a diffuse spike, or poly-spike, slow waves (< 2.0 Hz) pattern on electroencephalogram (EEG), and severe mental…
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Learning disorders
In dsm-iv-tr, this is a major group of infancy, childhood, and adolescence disorders that includes reading disorder, mathematics disorder, and disorder of written expression. Formerly known as academic skills disorders. One of a variety of disorders characterized by difficulty reading, writing, or using mathematical symbols that is two standard deviations below the norm for one’s…
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Learned helplessness
A condition in which a person attempts to establish and maintain contact with another by adopting a helpless, powerless stance. A condition created by exposure to inescapable aversive events retards or prevents learning in subsequent situations in which escape or avoidance is possible. A passive fatalistic behavior that one cannot influence one’s environment, or alter…