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Neurological Glossary

The glossary on this page is taken from the following resources and appears in the book: Caring For Your Child With Hydranencephaly. It is included here to help families with some of the terms they may encounter when learning about their child's condition. Glossary

Nervous System Diseases Health Guide Glossary

Medicine Net Medical Terms Dictionary

Apnea, obstructive sleep:
Sleep apnea is a breathing disorder characterized by brief interruptions of breathing during sleep. It owes its name to a Greek word, apnea, meaning "want of breath."

There are two types of sleep apnea: central and obstructive.

  • Central sleep apnea occurs when the brain fails to send the appropriate signals to the breathing muscles to initiate respirations.
  • Obstructive sleep apnea occurs when air cannot flow into or out of the person's nose or mouth although efforts to breathe continue.

Obstructive sleep apnea is much more common than central sleep apnea. In obstructive sleep apnea, the throat collapses during sleep causing the individual to snort and gasp for breath. Hundreds of these episodes can occur every night causing daytime sleepiness and, it is thought, increasing the risk of hypertension (high blood pressure) and heart problems.

Atrophy - wasting, shrinkage of muscle tissue or nerve tissue

Babinski reflex: An important neurologic test based, believe it or not, upon what the big toe does when the sole of the foot is stimulated. If the big toe goes up, that may mean trouble.

The Babinski reflex is obtained by stimulating the external portion (the outside) of the sole. The examiner begins the stimulation back at the heel and goes forward to the base of the toes. There are diverse ways to elicit Babinski response. A useful way that requires no special equipment is with firm pressure from the examiner's thumb. Just stroke the sole firmly with the thumb from back to front along the outside edge.

Care must be taken not to overdo it. Too vigorous stimulation may cause withdrawal of the foot or toe, which can be mistaken as a Babinski response.

The Babinski reflex is characterized by extension of the great toe and also by fanning of the other toes.

Most newborn babies are not neurologically mature and therefore show a Babinski response. Upon stimulation of the sole, they extend the great toe . Many young infants do this, too, and it is perfectly normal. However, in time during infancy the Babinski response vanishes and, under normal circumstances, should never return.

A Babinski response in an older child or adult is abnormal. It is a sign of a problem in the central nervous system (CNS), most likely in a part called the pyramidal tract.

Asymmetry of the Babinski response -- when it is present on one side but not the other -- is abnormal. It is a sign not merely of trouble but helps to lateralize that trouble (tell which side of the CNS is involved).

The Babinski reflex is known by a number of other names: the plantar response (because the sole is the plantar surface of the foot), the toe or big toe sign or phenomenon, the Babinski phenomenon or sign. (It is wrong to say that the Babinski reflex is positive or negative; it is present or absent).

Babinski, despite the Slavic sound of the name, was French: Joseph Francois Felix Babinski (1857-1932). He will never be forgotten in medicine, thanks to the reflex he found.

BAER (brainstem auditory evoked response):Measures function of Central Nervous System, including pathway from brainstem

Basal Ganglia: A series of structures located deep in the brain responsible for motor movements.

Blood-Brain Barrier - the protective membrane that separates circulating blood from brain cells.

Bradykinesia: The slowing of motor movements due to dysfunction of the basal ganglia and related structures.

Brain Attack - another term for stroke.

CAT Scan (computerized axial tomography): Pictures of structures within the body created by a computer that takes the data from multiple X-ray images and turns them in pictures on a screen. The CAT (computerized axial tomography) scan can reveal some soft-tissue and other structures that cannot even be seen in conventional X-rays. Using the same dosage of radiation as that of an ordinary X-ray machine, an entire slice of the body can be made visible with about 100 times more clarity with the CAT scan.

The "cuts" (tomograms) for the CAT scan are usually made 5 or 10 mm apart. The CAT machine rotates 180 degrees around the patient's body; hence, the term "axial." The machine sends out a thin X-ray beam at 160 different points. Crystals positioned at the opposite points of the beam pick up and record the absorption rates of the varying thicknesses of tissue and bone. The data are then relayed to a computer that turns the information into a 2-dimensional cross-sectional image.

CAT scanning is painless. Iodine-containing contrast material is sometimes used in CAT scanning. If you are having a CAT scan and are allergic to iodine or other radiocontrast materials, please notify your doctor and the radiology staff.

CAT scanning was invented in 1972 by the British engineer Godfrey N. Hounsfield (later Sir Godfrey) and the South African (later American) physicist Alan Cormack. CAT scanning was already in general use by 1979, the year Hounsfield and Cormack were awarded the Nobel Prize in Medicine or Physiology for its development.

The CAT scan is also known as the CT (computerized tomography) scan.

Cerebellum: The portion of the brain in the back of the head between the cerebrum and the brain stem. The cerebellum controls balance for walking and standing and other complex motor functions.

Cerebral Aneurysm: A defect that results in weakness in the wall of a blood vessel that can lead to bleeding in the brain.

Cerebral Embolism - a brain attack that occurs when a wandering clot (embolus) or some other particle forms in a blood vessel away from the brain -- usually in the heart.

Cerebral hemispheres: The two halves of the cerebrum, the largest part of the brain.

Cerebral Hemorrhage - a type of stroke occurs when a defective artery in the brain bursts, flooding the surrounding tissue with blood.

Cerebral Thrombosis - the most common type of brain attack, it occurs when a blood clot (thrombus) forms and blocks blood flow in an artery bringing blood to part of the brain.

Cerebrospinal fluid: CSF. A watery fluid, continuously produced and absorbed, which flows in the ventricles (cavities) within the brain and around the surface of the brain and spinal cord.

The CSF is produced by the choroid plexus, a series of infolded blood vessels projecting into the cerebral ventricles, and it is absorbed into the venous system.

If production exceedes absorption, the CSF pressure rises and the result is hydrocephalus. This can also occur if the CSF pathways are obstructed and CSF accumulates.

Cerebrovascular Disease: Disorders that affect the blood vessels that supply the brain that may result in a stroke.

Cerebrum - consists of two parts (lobes), left and right, which form the largest and most developed part of the brain; initiation and coordination of all voluntary movement take place within the cerebrum. The basal ganglia are located immediately below the cerebrum.

Central Nervous System: Refers to the brain and the spinal cord.

Cerebrospinal Fluid: The fluid that surrounds the brain and the spinal cord

Chorea - rapid, jerky, dance-like movement of the body.

Clonus: Brisk increase in tone with involuntary movements that result in dysfunction of the corticospinal tracts.

Coma: The state of unconsciousness in which patients lie unresponsive with the eyes closed.

Cortex - the outer layer of the cerebrum, densely packed with nerve cells.

Corticospinal Tract: The nervous system structures that begin in the brain and travel to the motor neuron cell to innervate the motor nerves.

Cryothalamotomy - a surgical procedure in which a supercooled probe is inserted into a part of the brain called the thalamus in order to stop tremors.

Deep Tendon Reflexes
: The deep muscle stretch reflexes that are obtained by tapping on the tendons (such as the "knee jerk").

Dementia: An acquired loss of cognitive function that may affect language, attention, memory, personality and abstract reasoning.

Demyelinating: An inflammatory process that disrupts the myelin coating of nervous system structures.

Dopamine - a chemical substance, a neurotransmitter, found in the brain that regulates movement, balance, and walking.

Dyskinesia - an involuntary movement including athetosis and chorea.

Dysphagia - difficulty in swallowing.

Dystonia - a slow movement or extended spasm in a group of muscles.

Dystrophin - a protein, a chemical substance made by muscle fibers.

Echocardiogram: A diagnostic test to detect abnormalities of the heart using an ultrasound probe to image the cardiac structures.

Edema: Swelling; fluid is retained resulting in swollen tissues.

EEG: (electroencephalography) The diagnostic test that is used to study the brain wave activity. It is most useful to evaluate the seizure disorders.

Embolus - a "wandering" blood clot.

EMG/NCV: (electromyography/nerve conduction study) A test that is used to study the nerves and muscles to help diagnose disorders that can affect them. A small needle is placed in the muscle in the EMG. Electrical conduction is studied in the NCV. The results are seen on an oscilloscope screen and compared to normal values.

Encephalitis: Inflammation or infection involving the brain.

Epilepsy - a brain disorder involving recurrent seizures; may also be called a seizure disorder.

Evoked Potentials: A series of electophysiologic tests that help to evaluate the function of specific elements of the nervous system involved in Multiple Sclerosis.

Extensor Muscle - any muscle that causes the straightening of a limb or other part.

Extrapyramidal System - system consisting of nerve cells, nerve tracts and pathways that connects the cerebral cortex, basal ganglia, thalamus, cerebellum, reticular formation, and spinal neurons that is concerned with the regulation of reflex movements such as balance and walking.

Flexor Muscle - any muscle that causes the bending of a limb or other body part.


Gadolinium: A contrast agent that is given intravenously during MRI (magnetic resonance imaging) to increase visualization of specific abnormalities.

Ganglion - a cluster of nerve cells.

Gray Matter - the darker-colored tissues of the central nervous system; in the brain, the gray matter includes the cerebral cortex, the thalamus, the basal ganglia, and the outer layers of the cerebellum.

: Weakness that affects one side of the body.

Hemorrhage: Bleeding; (such as in brain hemorrhage)

: Lack of blood flow; (such as in ischemic stroke)

- an exaggeration of the forward curve of the lower part of the back, sometimes called sway-back.

Lumbar Puncture: (also known as a spinal tap) A procedure that involves removing some of the cerebrospinal fluid from the base of the spine. The physician will first use a local anesthetic on the skin and soft tissues in the lower back. Cerebrospinal fluid is obtained from the spinal area using a small needle and a syringe.

Magnetic resonance imaging: A special radiology technique designed to image internal structures of the body using magnetism, radio waves, and a computer to produce the images of body structures. In magnetic resonance imaging (MRI), the scanner is a tube surrounded by a giant circular magnet. The patient is placed on a moveable bed that is inserted into the magnet. The magnet creates a strong magnetic field that aligns the protons of hydrogen atoms, which are then exposed to a beam of radio waves. This spins the various protons of the body, and they produce a faint signal that is detected by the receiver portion of the MRI scanner. A computer processes the receiver information, and an image is produced. The image and resolution is quite detailed and can detect tiny changes of structures within the body.

MRI images tend to be quite clear, particularly those of the soft tissue, brain and spinal cord, abdomen and joints, and they may be superior to routine X-ray images of such structures.

An MRI is painless and has the advantage of avoiding x-ray radiation exposure. There are no known risks of an MRI. The benefits of an MRI relate to its precise accuracy in detecting structural abnormalities of the body.

Patients with heart pacemakers, metal implants, or metal chips or clips in or around the eyes cannot be scanned with MRI because of the effect of the magnet. Metallic chips, materials, surgical clips, or foreign material (artificial joints, metallic bone plates, or prosthetic devices, etc.) can significantly distort the images obtained by the MRI scanner. Similarly, patients with artificial heart valves, metallic ear implants, bullet fragments, and chemotherapy or insulin pumps should also not have an MRI.

Claustrophobia can be a problem. For an MRI, patients lie in a closed area inside the magnetic tube. Some patients experience a feeling of claustrophobia.

In 2003 the Nobel Prize in Physiology or Medicine was awarded to the American Paul C. Lauterbur (1929-) and the Briton Sir Peter Mansfield (1933-) "for their discoveries concerning magnetic resonance imaging."

Malignant: Usually refers to tumors that are cancerous; may refer to a disease state that has a debilitating unremitting course.

Meningitis: Inflammation or infection of the meninges, which are the coverings of the brain.

Motor Neuron Cells: The cells located in the spinal cord that give rise to the nerves that supply the muscles.

MRI (magnetic resonance imaging): A technique that utilizes the properties of magnetic fields to provide images of the body

Myelin: The outer lipid rich (fatty) layer that covers nerves and nervous system pathways in the brain and spinal cord.

Myoclonus - jerking, involuntary movements of the arms and legs. May occur normally during sleep.

Myopathy: A disease resulting in dysfunction of the muscles usually causing weakness and atrophy.

: The nerve cells of the brain that carry out neurological function.

Neurotransmitters - chemical substances that carry impulses from one nerve cell to another; found in the space (synapse) that separates the transmitting neuron's terminal (axon) from the receiving neuron's terminal (dendrite).

NPH: (normal pressure hydrocephalus) Increase in pressure within the ventricles of the brain, causing dementia, gait difficulties and urinary incontinence.

Nystagmus: The jerking "to and fro" movement of the eyes that occurs when disorders affect the control of eye movement.



Peripheral Nervous System: Refers to the nerves and muscular structures

Plaque: The lesion that occurs in the "white matter" of the brain due to demyelination.

Prophylactic: Used to describe medications or treatments that are preventative in the treatment of disease.

Ptosis: Drooping of the eyelids due to weakness of the muscles responsible for keeping the lids open.

Range Of Motion
- the extent that a joint will move from full extension to full flexion.

Resting Tremor - a tremor of a limb that increases when the limb is at rest.

Rigidity: Stiffness in the limbs or body due to dysfunction of the basal ganglia and related structures.

: The abnormal electrical discharge of brain cells (neurons) that results in a transient disturbance in brain function.

SEP (Somatosensory Evoked Response):Measures function of Central Nervous System, including pathway from the extremities.

Serotonin: An important neurotransmitter (communicates information chemically between brain cells) that is involved in the pain disorders and emotional perceptions.

Sialorrhea - drooling.

Sleep Apnea: A disorder that results in apnea (cessation of breathing) during sleep often due to obstruction of the upper airway.

Spasticity: stiffness of the body involving the limbs that results from dysfunction of the corticospinal tracts.

Status Epilepticus: Seizures that continue for more than twenty minutes without an intervening period of responsiveness.

Subarachnoid Hemorrhage: Bleeding in the area surrounding the brain, that is usually a result of the rupturing of a cerebral aneurysm in the brain.

Sustention (Postural) Tremor - a tremor of a limb that increases when the limb is stretched.

Synapse - a tiny gap between the ends of nerve fibers across which nerve impulses pass from one neuron to another; at the synapse, an impulse causes the release of a neurotransmitter, which diffuses across the gap and triggers an electrical impulse in the next neuron.

Thrombus - a blood clot.

TIA: (Transient Ischemic Attack); Neurological symptoms occur due to transient interruption of the blood flow to the brain.

Torticollis: The involuntary turning of the neck to one side that can be seen in disorders of the basal ganglia.

Tremor - a rhythmical shaking of a limb, head, mouth, tongue, or other part of the body.

VER(Visual Evoked Responses)
: Measures function of Central Nervous System, including the pathway from optic tract.

Vertebrae: Bones that make up the spinal column.

White Matter: The lipid rich myelinated portion of the brain and spinal cord. Or: nerve tissue that is paler in color than gray matter because it contains nerve fibers with large amounts of insulating material (myelin). The white matter does not contain nerve cells. In the brain, the white matter lies within the gray layer of the cerebral cortex.


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