Have you come accross a medical term you don't understand? The concise glossary below offers you explanations of some medical terms you are likely to hear. If, however, you can't find the term you're looking for here, we suggest trying MedTerms online medical dictionary, or NeurologyChannel.com, extensive information source developed and monitored by board-certified physicians.

Attention-deficit/hyperactivity disorder (ADHD/ADD)
A psychiatric disorder and, more specifically, a chronic neurobehavioral syndrome. ADHD manifests as inattention, impulsivity, and hyperactivity. The term attention-deficit disorder (ADD) refers to the condition without hyperactivity.

Alzheimers Disease
The most common form of dementia in older persons that affects many areas of cognitive function. Specific pathological findings have been identified when the brain has been studied under the microscope, although no cure for the disorder has been found.

Amyotrophic Lateral Sclerosis
(ALS, motor neuron disease, Lou Gehrigs disease). A degenerative disorder affecting the motor neuron cells and the motor tracts in the brain and spinal cord.

Angiogram
An invasive diagnostic test that uses a special dye injected into the arteries by a catheter to visualize the blood vessels.

Aphasia
An aquired abnormality in the production or comprehension of language.

Arteries
The blood vessels that carry the oxygenated blood to the organs.

Atherosclerosis
Thickening of the arterial wall of blood vessels due to deposition of lipids (fats) and blood clots.

Atony
A lack of muscle tone, usually leading to temporary debilitation.

Atrial Fibrillation
An abnormal rhythm of the heart that can result in an increased risk of stroke due to the formation of emboli (blood clots) in the heart.

Atrophy
Shrinkage in size of a particular structure, such as muscle groups, or of the brain.

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Aura
Syptoms that occur prior to a particular neurological problem (such as seizure or migraine) that serve as a warning that the abnormal spell may follow. Includes disturbances in vision, smell or perception.

Autism
Also called infantile autism or autistic disorder, is a lifelong disorder that causes abnormal neurological development. Autism causes impaired social interaction, communication difficulties, and restricted or repetitive activities and interests.

Autoimmune
An abnormal response of the immune system, causing antibodies and immune mediated cells to attack parts of the body. This mechanism may explain many diseases.

Axon
The inner core of peripheral nerves.

BAER (brainstem auditory evoked response)
Measures function of Central Nervous System, including pathway from brainstem.
 
Baclofen Pump Therapy
Baclofen is a medication commonly used to decrease spasticity related to multiple sclerosis, spinal cord injuries, or other neurological diseases. Baclofen works by restoring the normal balance of electrical signals coming from the spinal cord through the nerves to the muscle, and reducing muscle hyperactivity.

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

Bell's Palsy
A neurological disorder caused by damage to the seventh cranial nerve, also known as the facial nerve, which results in weakness or paralysis on one side of the face. The paralysis causes distortion of facial features and interferes with normal functions, such as closing the eye and eating.

Benign
Usually used in the context of referring to tumors that are not cancerous.

Blepharospasm
The involuntary closure of the eyes and lids.

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Botulinum Toxin Injection
Botulinum toxin injection is used to treat dystonia—a neuromuscular disorder that produces involuntary muscle contractions, or spasm—that affects muscles that control movement in the eyes, neck, face, voice box, or the smooth muscle in the bladder.

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

Cataplexy
A symptom characterized by the sudden loss of postural tone, often resulting in the individual falling to the floor. Cataplexy is often part of the narcolepsy complex.

CAT Scan (computerized axial tomography)
A specialized X-ray examination that is often used to visualize the brain and spinal structures.

Cerebral Palsy
In cerebral palsy, faulty development or damage to motor areas in the brain impair the body's ability to control movement and posture. This results in a number of chronic neurological disorders. Cerebral palsy is usually associated with events that occur before or during birth, but may be acquired during the first few months or years of life as the result of head trauma or infection.

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

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

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

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

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

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Cluster Headache
A syndrome that is more common in males resulting in one sided severe pain around the eye which usually occurs at night and is associated with nasal stuffiness, and tearing of the eye.

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

Corticography
Direct recordings of brain activity from the surface of the cortex, usually during brain surgery.

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

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.

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. In an EEG, electrodes are placed on the scalp over multiple areas of the brain to detect and record patterns of electrical activity and check for abnormalities in the electrical activity of the brain.

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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 chronic neurological condition characterized by recurrent seizures that are caused by abnormal cerebral nerve cell activity.

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

Fasciculation
Twitching of the muscles that is seen in diseases involving the peripheral nervous system.

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

Guillain-Barre Syndrome (GBS)
An inflammatory disorder of the peripheral nerves. GBS is characterized by weakness and numbness or tingling in the legs and arms, and possible loss of movement and feeling in the legs, arms, upper body, and face.

Hemiparesis
Weakness that affects one side of the body.

Hemorrhage
Bleeding; (such as in brain hemorrhage).

HIV (human immunodeficiency virus)
This is the virus that affects the immune system and causes the disease known as AIDS (acquired immunodeficiency disorder).

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Infectious Diseases
Any disease caused by the entrance, growth, and multiplication of bacteria or protozoans in the body; a germ disease. Examples are Lyme Disease, Meningitis, and many others. An infectious disease may not be contagious. Sometimes, as distinguished from contagious disease, such a disease communicated by germs carried in the air or water, and thus spread without contact with the patient, as measles.

Insomnia
A complex symptom that results from insufficient sleep or sleep of poor quality.

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

Jet Lag (desynchronosis)
a temporary condition that some people experience following air travel across several time zones in a short period of time. This causes the traveler's internal clock to be out of sync with the external environment.

Ketogenic Diet
The ketogenic diet tries to make the body use more fat for energy (instead of sugar, or glucose) and thus produce more ketones by feeding the body lots of fat and limiting carbohydrates. The ketogenic diet may sometimes be used to treat children with severe seizures who have not responded to antiepileptic medications.

Lyme Disease
A disease that affects the joints, nervous system and heart that is transmitted by the deer tick, and is caused by a parasite known as a Borrelia.

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.

Lacunar
A subtype of stroke that affects the deeper parts of the brain and involves the tiny perforating arteries.

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

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

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

Metastatic
Usually used to describe cancerous lesions that spread to other organs in the body.

Migraine
A headache syndrome characterized by throbbing, usually one sided pain, that may be associated with nausea, vomiting and visual disturbances.

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

Movement Disorders
Movement disorders describe a group of neurological disorders that involve the motor and movement systems. Some of the more commonly known diseases include Parkinson's disease, tremors, dystonias, Huntingtons Chorea and Tourettes syndrome.

Multi-infarct Dementia
A dementia that is caused by the cumulative affect of having had many strokes in the brain.

Multiple Sclerosis (MS)
A chronic, progressive, degenerative disorder that affects nerve fibers in the brain and spinal cord. A fatty substance (called myelin) surrounds and insulates nerve fibers and facilitates the conduction of nerve impulse transmissions. MS is characterized by intermittent damage to myelin (called demyelination) caused by the destruction of specialized cells (oligodendrocytes) that form the substance.

Muscular Dystrophy
A congenital (hereditary) disorder of the muscles resulting in weakness and dysfunction of the muscles.

Myasthenia Gravis
A disorder affecting the space between the nerve and the muscle (neuromuscular junction) that results in transient motor weakness of the face and limbs. Due to an autoimmune process affecting the chemical acetylcholine.

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

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

Narcolepsy
A syndrome that is often hereditary, and characterized by repeated attacks of sudden sleep that may be associated with other specific abnormalities making up the narcolepsy complex.

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

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

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

Paraneoplastic
Disorders that occur due to the remote effects of cancer, such as through the mechanism of hormonal or antibody production.

Paresthesias
Unusual sensory symptoms of tingling, numbness or other abnormal feelings of sensation.

Peripheral Nervous System
Refers to the nerves and muscular structures.

Peripheral Neuropathy
A general term referring to disorders of peripheral nerves. The peripheral nervous system is made up of the nerves that branch out of the spinal cord to all parts of the body. Peripheral neuropathy can be associated with poor nutrition, a number of diseases, and pressure or trauma.

Photophobia
Literally means "fear of light", but the term is used when bright light is bothersome to individuals. Often occurs in syndromes such as migraine headache.

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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.

Radiculopathy
Irritation and inflammation of one of the nerve roots in the vicinity of the spinal column.

REM (rapid eye-movement sleep)
The stage of sleep that is characterized by decreased muscle tone, rapid eye movements and dreaming.

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

Sciatic Nerve
A large nerve in the lumbar-sacral spine region that is composed of multiple nerve roots that supply the lower extremities.

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

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

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

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Sleep Walking
A common arousal disorder that is especially prevalent among children. Sleepwalkers (somnambulists) are aroused out of their deep sleep during motor activity, which usually includes, but is not limited to, walking.

SEP (somatosensory evoked response)
Measures function of Central Nervous System, including pathway from the extremities.

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

Spinal Stenosis
A syndrome that results in narrowing of the dimensions of the spinal canal due to disc disease, bony changes ligamentous thickening and congenital factors.

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.

Tensilon Test
A diagnostic test that is used to confirm the disease myasthenia gravis. A substance that interferes with the breakdown of acetycholine is injected intravenously, and the response is monitored.

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.

T.O.V.A. (test of variables of attention)
A computerized assessment of visual attention.

Toxoplasmosis
A parasitic disease that affects the brain that occurs in patients who are immunosuppressed (such as those individuals with AIDS).

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Tremor
Disorder that involves abnormal involuntary movement. The part of the body involved oscillates around a particular point in space.

Tumor
An abnormal, spontaneous growth of new tissue. Tumors are either benign, noncancerous tumors that do not spread to other tissues or parts of the body or malignant, cancerous tumors that invade other tissues and parts of the body.

Vagus Nerve Stimulation (VNS)
Vagus nerve stimulation involves the implantation of a generator that stimulates the vagus nerve and thus reduces seizure activity.

VER (visual evoked responses)
Measures function of central nervous system, including the pathway from optic tract.

Vertebrae
Bones that make up the spinal column.

Vertigo
Dizziness or imbalance that often has a spinning or rotational component.

Vestibular System
The parts of the nervous system that control equilibrium and balance.

White Matter
The lipid rich myelinated portion of the brain and spinal cord.

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