Neurological Conditions

Definitions - Neurological Conditions - A

There are many conditions classified or defined as Neurological Conditions. This list covers those definitions beginning with the letter A.

Absence of the Septum Pellucidum - The septum pellucidum (SP) is a thin membrane located at the midline of the brain. Children who are born without this membraine and also have other abnormalities, pituitary  deficiencies and abnormal development of the optic disk have a disorder known as septo-optic dysplasia.

Acid Lipase Disease -  is a name used to describe two related disorders of fatty acid metabolism. Acid lipase disease occurs when the enzyme needed to break down certain fats that are normally digested by the  body is lacking or missing, resulting in the toxic buildup of these fats in the body’s cells and tissues. These fatty substances, called lipids, include waxes, oils, and cholesterol.

Acid Maltase Deficiency - Glycogen storage disease type II (also called Pompe disease or acid maltase deficiency) is a rare genetic disorder caused by a deficiency in the enzyme acid alpha-glucosidase (GAA) (EC  3.2.1.20), which is needed to break down glycogen, a stored form of sugar used for energy.

Acquired Epileptiform Aphasia - Landau-Kleffner syndrome (LKS) is a rare, childhood neurological disorder characterised 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.

Acute Disseminated Encephalomyelitis - is an immune mediated disease of brain. It usually occurs following a viral infection or vaccination, but it may also appear spontaneously. It is similar in some ways to multiple  sclerosis, and is considered part of the Multiple sclerosis borderline.

ADHD - Attention-Deficit Hyperactivity Disorder (ADHD), or Hyperkinetic Disorder as officially known in the UK (though ADHD is more commonly used), is generally considered to be a developmental disorder, largely  neurological in nature, affecting about 5% of the world's population.

Adie's Pupil - is a neurological condition of unknown origin with an unusual, asymmetric presentation known as anisocoria, an inequality in the size of the pupils of the eyes. It is believed to be a result of damage to  the nerve innervating a muscle of the eye known as the ciliary body. Alternately, the problem may be located at the ciliary ganglion, a kind of nerve junction structure from which the nerve to the ciliary body runs.

Adie's Syndrome - also Adie's syndrome, Adie's Tonic Pupil or Holmes-Adie's syndrome, is caused by damage to the postganglionic fibers of the parasympathetic innervation of the eye and characterized by a  tonically dilated pupil. It most commonly affects younger women and is unilateral in 80% of cases. The pupil is characteristically poorly reactive to light but slowly reactive to accommodation. Signs and symptoms  may/can include blurry vision due to accommodative paresis, photophobia and difficulty reading.

Adrenoleukodystrophy - is one of a group of genetic disorders called the leukodystrophies that cause damage to the myelin sheath, an insulating membrane that surrounds nerve cells in the brain. People with ALD  accumulate high levels of saturated, very long chain fatty acids (VLCFA) in the brain and adrenal cortex because they do not produce the enzyme that breaks down these fatty acids in the normal manner. The loss of  myelin and the progressive dysfunction of the adrenal gland are the primary characteristics of ALD.

Agenesis of the Corpus Callosum - (ACC) is a rare birth defect (congenital disorder) in which there is a complete or partial absence of the corpus callosum. Agenesis of the corpus callosum occurs when the corpus  callosum, the band of tissue connecting the two hemispheres of the brain, does not develop typically in utero. In addition to agenesis of the corpus callosum, other callosal disorders include hypogenesis (partial  formation), dysgenesis (malformation) of the corpus callosum, and hypoplasia (underdevelopment) of the corpus callosum.

Agnosia - is a loss of ability to recognize objects, persons, sounds, shapes, or smells while the specific sense is not defective nor is there any significant memory loss. It is usually associated with brain injury or  neurological illness, particularly after damage to the right parietal lobe.

Aicardi Syndrome - is a rare genetic disorder. Aicardi syndrome is characterized by the following: Absence of the corpus callosum, either partial or complete (the corpus callosum is the part of the  brain which sits between the right and left sides of the brain and allows the right side to communicate with the left.) Infantile spasms (a form of seizures) Lesions or "lacunae" of the retina of the eye that are very  specific to this disorder. Other types of defects of the brain such as microcephaly, (small brain); enlarged ventricles; or porencephalic cysts (a gap in the brain where there should be healthy brain tissue). Aicardi  syndrome only affects females, and in very rare cases, males with Klinefelter syndrome (XXY).

AIDS - Neurological complications are common in HIV disease. The spectrum of neurological disorders is broad and involves the central nervous system, or CNS (brain and spinal cord) and the peripheral nervous  system, or PNS (nerves outside the brain and spinal cord, and related muscle).

Alexander Disease - is a slowly progressing and fatal neurodegenerative disease. It is a very rare disorder which results from a genetic mutation and mostly affects infants and children, causing developmental delay  and changes in physical characteristics.

Alpers' Disease - is a rare degenerative disease of the brain involving the grey matter. It is characterised by acute onset of severe convulsions leading to rapid intellectual and bodily breakdown. Other traits are  blindness, deafness, myoclonus, spasticity, choroathetosis, cerebellar ataxia, growth retardation, plus terminal decortication. Manifests in early childhood and usually causes death within months.

Alternating Hemiplegia - Alternating hemiplegia is a rare neurological disorder that develops in childhood, usually before the first 4 years. The disorder is characterized by recurrent but temporary episodes of paralysis  on one side of the body.

Alzheimer's Disease - (AD) is a slowly progressive disease of the brain that is characterized by impairment of memory and eventually by disturbances in reasoning, planning, language, and perception.

Amyotrophic Lateral Sclerosis - (ALS) is a disease of unknown cause characterized by slowly progressive degeneration of upper (UMN) and lower motor neurons (LMN). The UMN findings include hyperreflexia and  spasticity. They result from degeneration of the lateral corticospinal tracts in the spinal cord. The LMN findings include weakness, atrophy, and fasciculations. ALS is eventually fatal because of respiratory muscle  weakness.

Anencephaly - is a condition present at birth that affects the formation of the brain and skull bones surrounding the head. Often, the brain lacks part or all of the cerebrum. There is no bony covering over the back of  the head and there may also be missing bones around the front and sides of the head.

Aneurysm - An aneurysm (or anneurism) is a localized, blood-filled dilation of a blood vessel caused by disease or weakening of the vessel wall. Aneurysms most commonly occur in arteries at the base of the brain   and in the aorta (the main artery coming out of the heart). The bulge in a blood vessel can burst and lead to death at any time. The larger an aneurysm becomes, the more likely it is to burst. Aneurysms can usually  be treated.

Angelman Syndrome - Symptoms of Angelman syndrome are learning disability, jerky movements, a tendency to seizures and a happy, sociable personality. Children with Angelman syndrome often do not learn to sit  until around one year of age. The majority of children will learn to walk but with a stiff legged gait. Many children with Angelman syndrome have a  facial appearance with a wide, smiling mouth, deep set eyes and  prominent chin. These features become more prominent as children get older.

Angiomatosis - refers to little knots of capillaries in various organs. These tend to be cavernous hemangiomas, which are sharply defined, sponge-like tumors composed of large, dilated, cavernous vascular spaces.

Anoxia - Hypoxia is a pathological condition in which the body as a whole (generalised hypoxia) or region of the body (tissue hypoxia) is deprived of adequate oxygen supply. Hypoxia in which there is complete  deprivation of oxygen supply, is referred to as anoxia. In the case of altitude sickness, where hypoxia develops gradually, the symptoms include headaches, fatigue, shortness of breath, a feeling of euphoria and  nausea. In severe hypoxia, or hypoxia of very rapid onset, changes in levels of consciousness, seizures, coma and death occur.

Antiphospholipid Syndrome - (APS) is a disorder characterized by recurrent venous or arterial thrombosis and/or fetal losses associated with characteristic laboratory abnormalities, such as persistently elevated levels  of antibodies directed against membrane anionic phospholipids (ie, anticardiolipin [aCL] antibody, antiphosphatidylserine) or their associated plasma proteins, predominantly beta-2 glycoprotein I (apolipoprotein H), or  evidence of a circulating anticoagulant.

Aphasia - (or aphemia) is a loss of the ability to produce and/or comprehend language, due to injury to brain areas specialized for these functions. It is not a result of deficits in sensory, intellect, or psychiatric  functioning. Depending on the area and extent of the damage, someone suffering from aphasia may be able to speak but not write, or vice versa, or display any of a wide variety of other deficiencies in language  comprehension and production, such as being able to sing but not speak. Aphasia may co-occur with speech disorders such as dysarthria or apraxia of speech.

Apraxia - is a neurological disorder characterized by loss of the ability to execute or carry out learned purposeful movements, despite having the desire to and the physical ability to perform the movements. It is a  disorder of motor planning which may be acquired or developmental, but may not be caused by incoordination, sensory loss, or failure to comprehend simple commands.

Arachnoid Cysts - represent benign cysts that occur in the cerebrospinal axis in relation to the arachnoid membrane and do not communicate with the ventricular system. They usually contain clear, colorless fluid  that is most likely normal cerebrospinal fluid, but they rarely contain xanthochromic fluid. Arachnoid cysts also occur within the spinal canal, in which arachnoid cysts or arachnoid diverticula may be located  subdurally or in the epidural space. Spinal arachnoid cysts are commonly located dorsal to the cord in the thoracic region.

Arachnoiditis - is a neuropathic disease caused by the inflammation of the arachnoid, one of the membranes that surround and protect the nerves of the central nervous system, including the brain and spinal cord. The  arachnoid can become inflamed because of an irritation from chemicals, infection from bacteria or viruses, as the result of direct injury to the spine, chronic compression of spinal nerves, or complications from spinal  surgery or other invasive spinal procedures.

Arnold-Chiari Malformation - sometimes referred to as Chiari II malformation or ACM, is a congenital malformation of the brain. It occurs in almost all children born with both spina bifida and hydrocephalus. The  cerebellar tonsils are elongated and pushed down through the opening of the base of the skull blocking the flow of cerebrospinal fluid (CSF). The brainstem, cranial nerves, and the lower portion of the cerebellum may  be stretched or compressed.

Arteriovenous Malformation - (AVMs) are defects of the circulatory system that are generally believed to arise during embryonic or fetal development or soon after birth.  Although AVMs can develop in many different  sites, those located in the brain or spinal cord can have especially widespread effects on the body.  Most people with neurological AVMs experience few, if any, significant symptoms.  The malformations tend to be  discovered only incidentally, usually either at autopsy or during treatment for an unrelated disorder.

Asperger Syndrome - also called Asperger's syndrome, Asperger's disorder, Asperger's or AS) is one of several autism spectrum disorders (ASD) characterized by difficulties in social interaction and by restricted,  stereotyped interests and activities. AS is distinguished from the other ASDs in having no general delay in language or cognitive development.

Ataxia - Friedreich's ataxia is an inherited disease that causes progressive damage to the nervous system resulting in symptoms ranging from gait disturbance and speech problems to heart disease. Coordination  problems such as clumsy or awkward movements and unsteadiness, occurs in many different diseases and conditions. The ataxia of Friedreich's ataxia results from the degeneration of nerve tissue in the spinal cord  and of nerves that control muscle movement in the arms and legs. The spinal cord becomes thinner and nerve cells lose some of their myelin sheath, the insular covering on all nerve cells that helps conduct nerve  impulses.

Ataxia Telangiectasia - is a rare, childhood neurological disorder that causes degeneration in the part of the brain that controls motor movements and speech. Its most unusual symptom is an acute sensitivity to  ionizing radiation, such as X-rays or gamma-rays. The first signs of the disease, which include delayed development of motor skills, poor balance, and slurred speech, usually occur during the first decade of life.

Ataxias and Cerebellar or Spinocerebellar Degeneration - (SCA) is a genetic disease with multiple types, each of which could be considered a disease in its own right. Spinocerebellar ataxia (SCA) is one of a group of  genetic disorders characterized by slowly progressive incoordination of gait and often associated with poor coordination of hands, speech, and eye movements. Frequently, atrophy of the cerebellum occurs.

Atrial Fibrillation and Stroke - Atrial fibrillation is a rapid uncoordinated generation of electrical impulses by the atria of the heart. The most serious side effect of atrial fibrillation is stroke. Half of all strokes associated  with atrial fibrillation are major and disabling.

Autism - is a brain development disorder that impairs social interaction and communication, and causes restricted and repetitive behavior, all starting before a child is three years old. This set of signs  distinguishes autism from milder autism spectrum disorders (ASD) such as Asperger syndrome. Autism is highly heritable, although the genetics of autism are complex and it is generally unclear which genes are  responsible.

Autonomic Dysfunction - refers to a disorder of autonomic nervous system (ANS) function. Most physicians view dysautonomia in terms of failure of the sympathetic or parasympathetic components of the ANS, but  dysautonomia involving excessive ANS activities also can occur. Dysautonomia can be local, as in reflex sympathetic dystrophy, or generalized, as in pure autonomic failure. It can be acute and reversible, as in  Guillain-Barre syndrome, or chronic and progressive. Several common conditions such as diabetes and alcoholism can include dysautonomia.

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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