Neurological Conditions

Definitions - Neurological Conditions - H

Definitions of Neurological Conditions These definitions begin with the letter H.

Hallervorden-Spatz Disease - Neurodegeneration with brain iron accumulation (NBIA) is a rare, inherited, neurological movement disorder characterized by progressive degeneration of the nervous system. Symptoms, which vary greatly among patients and usually develop during childhood, may include slow writhing, distorting muscle contractions of the limbs, face, or trunk, choreoathetosis (involuntary, purposeless jerky muscle movements), muscle rigidity (uncontrolled tightness of the muscles), spasticity (sudden, involuntary muscle spasms), ataxia (inability to coordinate movements), confusion, disorientation, seizures, stupor, and dementia.

Head Injury - Head injuries include both injuries to the brain and those to other parts of the head, such as the scalp and skull. Head injuries may be closed or open. A closed (non-missile) head injury is one in which the skull is not broken. A penetrating head injury occurs when an object pierces the skull and breaches the dura mater. Brain injuries may be diffuse, occurring over a wide area, or focal, located in a small, specific area.

Headache - There are four types of headache: vascular, muscle contraction (tension), traction, and inflammatory. The most common type of vascular headache is migraine. Migraine headaches are usually characterized by severe pain on one or both sides of the head, an upset stomach, and, at times, disturbed vision. Women are more likely than men to have migraine headaches. After migraine, the most common type of vascular headache is the toxic headache produced by fever. Other kinds of vascular headaches include "cluster” headaches, which cause repeated episodes of intense pain, and headaches resulting from high blood pressure. Muscle contraction headaches appear to involve the tightening or tensing of facial and neck muscles. Traction and inflammatory headaches are symptoms of other disorders, ranging from stroke to sinus infection. Like other types of pain, headaches can serve as warning signals of more serious disorders.

Hemicrania Continua - Hemicrania continua is a rare form of chronic headache marked by continuous pain on one side of the face that varies in severity. Superimposed on the continuous but fluctuating pain are occasional attacks of more severe pain. Symptoms fall into two main categories: autonomic, including runny nose, tearing, eye redness, eye discomfort, sweating, and swollen and drooping eyelids; and migraine-like, including nausea, vomiting, and sensitivity to light and sound.

Hemifacial Spasm - Hemifacial spasm is a neuromuscular disorder characterized by frequent involuntary contractions of the muscles on one side of the face. The disorder occurs in both men and women, although it more frequently affects middle-aged or elderly women. The first symptom is usually an intermittent twitching of the eyelid muscle that can lead to forced closure of the eye.

Hemiplegia Alterans - 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. The paralysis can affect eye movements, limbs, or facial muscles.

Hereditary Neuropathies - Hereditary neuropathies are a group of inherited disorders of the peripheral nervous system. Within the group there are 4 subcategories of disorders, including hereditary motor and sensory neuropathy, hereditary sensory neuropathy, hereditary motor neuropathy, and hereditary sensory and autonomic neuropathy. Symptoms of these disorders vary and may include numbness and tingling in the feet and hands, muscle weakness (especially in the distal muscles), scoliosis, thin lower legs, foot deformities, insensitivity to pain, and autonomic symptoms such as impaired sweating, postural hypotension, and skin blotching.

Hereditary Spastic Paraplegia - Hereditary spastic paraplegia (HSP), also called familial spastic paraparesis (FSP), refers to a group of inherited disorders that are characterized by progressive weakness and stiffness of the legs.

Heredopathia Atactica Polyneuritiformis - Adult Refsum disease (ARD) is one of a group of genetic diseases called leukodystrophies, which damage the white matter of the brain and affect motor movements. Due to a genetic abnormality, people with ARD disease lack the enzyme that breaks down phytanic acid, a substance commonly found in foods. As a result, toxic levels of phytanic acid build up in the brain, blood, and other tissues.

Herpes Zoster - Shingles (herpes zoster) is an outbreak of rash or blisters on the skin that is caused by the same virus that causes chickenpox — the varicella-zoster virus. The first sign of shingles is often burning or tingling pain, or sometimes numbness or itch, in one particular location on only one side of the body. After several days or a week, a rash of fluid-filled blisters, similar to chickenpox, appears in one area on one side of the body. Shingles pain can be mild or intense.

Herpes Zoster Oticus - also called Ramsay Hunt Syndrome or Ramsay Hunt Syndrome type II, is a common complication of shingles. Shingles is an infection caused by the varicella-zoster virus, which is the virus that causes chickenpox. Shingles occurs in people who have had chickenpox and represents a reactivation of the dormant varicella-zoster virus. Herpes zoster oticus, which is caused by the spread of the varicella-zoster virus to facial nerves, is characterized by intense ear pain, a rash around the ear, mouth, face, neck, and scalp, and paralysis of facial nerves.

Hirayama Syndrome - Monomelic amyotrophy (MMA) is characterized by progressive degeneration and loss of motor neurons, the nerve cells in the brain and spinal cord that are responsible for controlling voluntary muscles. It is characterized by weakness and wasting in a single limb, usually an arm and hand rather than a foot and leg. There is no pain associated with MMA. While some physicians contend that mild sensory loss may be associated with this disease, many experts suggest that such symptoms actually indicate a cause other than MMA. MMA occurs in males between the ages of 15 and 25.

Holmes-Adie syndrome - (HAS) is a neurological disorder affecting the pupil of the eye and the autonomic nervous system. It is characterized by one eye with a pupil that is larger than normal and constricts slowly in bright light (tonic pupil), along with the absence of deep tendon reflexes, usually in the Achilles tendon. HAS is thought to be the result of a viral or bacterial infection that causes inflammation and damage to neurons in the ciliary ganglion, an area of the brain that controls eye movements, and the spinal ganglion, an area of the brain involved in the response of the autonomic nervous system. HAS begins gradually in one eye, and often progresses to involve the other eye. At first, it may only cause the loss of deep tendon reflexes on one side of the body, but then progress to the other side. The eye and reflex symptoms may not appear at the same time. People with HAS may also sweat excessively, sometimes only on one side of the body.

Holoprosencephaly - is a type of cephalic disorder. This is a disorder characterized by the failure of the prosencephalon (the forebrain of the embryo) to develop. During normal development the forebrain is formed and the face begins to develop in the fifth and sixth weeks of human pregnancy.

HTLV-1 Associated Myelopathy - For several decades the term “tropical spastic paraparesis” (TSP) has been used to describe a chronic and progressive disease of the nervous system that affects adults living in equatorial areas of the world and causes progressive weakness, stiff muscles, muscle spasms, sensory disturbance, and sphincter dysfunction. The cause of TSP was obscure until the mid-1980s, when an important association was established between the human retrovirus — human T-cell lymphotrophic virus type 1 (also known as HTLV-1) — and TSP. TSP is now called HTLV-1 associated myelopathy/ tropical spastic paraparesis or HAM/TSP. The HTLV-1 retrovirus is thought to cause at least 80 percent of the cases of HAM/TSP by impairing the immune system.

Hughes Syndrome - Antiphospholipid syndrome (APS or APLS) or antiphospholipid antibody syndrome is a disorder of coagulation, which causes blood clots (thrombosis) in both arteries and veins, as well as pregnancy-related complications such as miscarriage, preterm delivery, or severe preeclampsia.

Huntington's Disease - is caused by a trinucleotide repeat expansion in the gene coding for Huntingtin protein (Htt) and is one of several polyglutamine diseases. This expansion produces an altered form of the Htt protein, mutant Huntingtin (mHtt), which results in neuronal cell death in select areas of the brain. Huntington's disease itself isn't a terminal illness, but complications caused by it reduce life expectancy.

Hydranencephaly - Hydranencephaly is a rare condition in which the brain's cerebral hemispheres are absent and replaced by sacs filled with cerebrospinal fluid. An infant with hydranencephaly may appear normal at birth. The infant's head size and spontaneous reflexes such as sucking, swallowing, crying, and moving the arms and legs may all seem normal. However, after a few weeks the infant usually becomes irritable and has increased muscle tone. After a few months of life, seizures and hydrocephalus (excessive accumulation of cerebrospinal fluid in the brain) may develop. Other symptoms may include visual impairment, lack of growth, deafness, blindness, spastic quadriparesis (paralysis), and intellectual deficits.

Hydrocephalus - is a term derived from the Greek words "hydro" meaning water, and "cephalus" meaning head, and this condition is sometimes known as "water in the brain". People with this condition have abnormal accumulation of cerebrospinal fluid (CSF) in the ventricles, or cavities, of the brain. This may cause increased intracranial pressure inside the skull and progressive enlargement of the head, convulsion, and mental disability.

Hydromyelia - refers to an abnormal widening of the central canal of the spinal cord that creates a cavity in which cerebrospinal fluid (commonly known as spinal fluid) can accumulate. As spinal fluid builds up, it may put abnormal pressure on the spinal cord and damage nerve cells and their connections. Hydromyelia is sometimes used interchangeably with syringomyelia, the name for a condition that also involves cavitation in the spinal cord. In hydromyelia, the cavity that forms is connected to the fourth ventricle in the brain, and is almost always associated with infants and children who have hydrocephalus or birth defects such as Chiari Malformation II and Dandy-Walker Malformation. Syringomyelia, however, features a closed cavity and occurs primarily in adults, the majority of whom have Chiari Malformation II or have experienced spinal cord trauma. Symptoms, which may occur over time, include weakness of the hands, arms, and legs; and sensory loss in the neck and arms.

Hypersomnia - is characterized by recurrent episodes of excessive daytime sleepiness or prolonged nighttime sleep. Different from feeling tired due to lack of or interrupted sleep at night, persons with hypersomnia are compelled to nap repeatedly during the day, often at inappropriate times such as at work, during a meal, or in conversation. These daytime naps usually provide no relief from symptoms. Patients often have difficulty waking from a long sleep, and may feel disoriented. Other symptoms may include anxiety, increased irritation, decreased energy, restlessness, slow thinking, slow speech, loss of appetite, hallucinations, and memory difficulty.

Hypertonia - is a condition marked by an abnormal increase in the tightness of muscle tone and a reduced ability of a muscle to stretch (i.e. an increased stiffness). It is generally accompanied by (increased) spasticity of the particular muscles.

Hypotonia - is a medical term used to describe decreased muscle tone (the amount of resistance to movement in a muscle). It is not the same as muscle weakness, although the two conditions can co-exist. Hypotonia may be caused by trauma, environmental factors, or by genetic, muscle, or central nervous system disorders, such as Down syndrome, muscular dystrophy, cerebral palsy, Prader-Willi syndrome, myotonic dystrophy, and Tay-Sachs disease. Sometimes it may not be possible to find what causes hypotonia. Infants with hypotonia have a floppy quality or “rag doll” appearance because their arms and legs hang by their sides and they have little or no head control. Other symptoms of hypotonia include problems with mobility and posture, breathing and speech difficulties, lethargy, ligament and joint laxity, and poor reflexes.

Hypoxia - is a restriction in blood supply (and therefore oxygen supply) to an organ or section of the body, generally due to constriction or blocking of blood vessels.

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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