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Glossary of Spine- and Brain-related Terms

Glossary of Spine- and Brain-related Terms | American Association of Neurological Surgeons

Abscess – A circumscribed collection of pus in any part of the body, usually accompanied by swelling and inflammation.
Acoustic Neuromas – A benign tumor in the nerve that connects the ear to the brain.
Acromegaly – A disorder marked by progressive enlargement of the head, face, hands, feet and thorax, due to the excessive secretion of growth hormone.
Adenoma – A benign growth made of glandular tissue.
Agnosia – Absence of the ability to recognize the form and nature of persons and things.
Agraphia – Inability to write due either to muscular incoordination or an inability to phrase thought; results from brain disease.
Amaurosis – Loss of vision without a visible lesion in the eye structures or optic nerve.
Amaurosis Fugax – Temporary blindness occurring in short periods; caused by temporary lack of blood flow to the retina.
Amenorrhea – Absence of the menstrual period due to causes other than pregnancy or menopause.
Amnesia – Loss of memory caused by brain damage or by severe emotional trauma.
Analgesia – Loss of sensitivity to pain or loss of response to a painful stimulus; achieved by the use of an analgesic, or painkiller.
Anaplasia – A body cell's reversion to a more primitive condition; often a characteristic of malignant tumors.
Anastomosis – A surgical connection of nerves or blood vessels in the nervous system.
Anesthesiologist – Physician who administers pain-killing medications during surgery.
Anencephaly – Absence of the greater part of the brain, skull and scalp.
Anesthesia – Loss of sensation in a body part induced by the administration of a drug.
Anesthesiologist – Physician who administers anesthesia prior to surgery; also monitors reactions and complications during surgery.
Aneurysm – Dilation of an artery, formed by a circumscribed enlargement of its wall.
Angiogram – A medical imaging report that depicts the blood vessels traveling to and within the brain; test usually is performed by injecting a special dye through a catheter.
Angiography – Radiography of blood vessels using the injection of material opaque to X-rays to increase visibility of the vessels.
Anorexia – An eating disorder marked by excessive weight loss due to the restriction of food intake; spurred by distorted body image and other factors.
Anosmic – To be without the sense of smell.
Anoxia – A decrease in the level of oxygen to an organ or tissue.
Anti-Coagulant – A medication that prevents blood clotting.
Antidiuretic – A drug that helps to reduce urination.
Aphasia - Difficulty with or loss of the use of language; failure to understand the written, printed or spoken word not related to intelligence, but to specific lesions in the brain.
Apnea – An interruption in breathing.
Apoplexy – A condition in which there is bleeding into an organ or blood flow to an organ has ceased.
Arachnoid Mater – One of the three meninges that cover the brain and spinal cord, it is the delicate middle layer of these three membranes.
Arachnoiditis – Inflammation of the arachnoid membrane.
Arteriosclerosis – Thickening and calcification (buildup of calcium) of the arterial wall with loss of elasticity and contractility; also known as a hardening of the arteries.
Arteriovenous – Term used when a condition relates to arteries and/or veins.
Arteriovenous Malformation – Tangle of abnormal and poorly formed blood vessels (arteries and veins) with an innate propensity to bleed.
Astrocyte – A cell that supports the nerve cells (neurons) of the brain and spinal cord.
Astrocytoma – Tumor within the brain or spinal cord made up of astrocytes; ranges from slow-growing to rapid-growing.
Ataxia – A loss of voluntary muscle coordination.
Athetosis – A condition in which there is a succession of slow, writhing, involuntary movements of the fingers and hands, and sometimes of the toes and feet.
Atrophy – A wasting of the tissues in a body part.
Autonomic Nervous System – A system of nerve cells whose activities are beyond voluntary control; also termed the vegetative nervous system.
Avascular – A term used to indicate that a body part is not associated with or does not provide blood vessels.
Axon – A part of a nerve cell that conducts electrical signals to other nerves or structures.

Bactericidal – A term used to define a substance that kills bacteria.
Bacteriostatic Agent – An agent that inhibits the growth of bacteria.
Bell's Palsy – Paralysis of facial muscles (usually one side) due to a facial nerve damage or dysfunction.
Biopsy – Removal of a small portion of tissue for examination; performed for the purpose of making a diagnosis.
Blood-Brain Barrier – The barrier that exists between the blood and the cerebrospinal fluid that prevents the passage of various substances from the bloodstream to the brain.
Bradycardia – Slowness of the heart rate.
Bradykinesia – Slowness in movement; can be a symptom of nervous system disorders such as Parkinson's disease.
Brown-Sequard's Syndrome – Loss of sensation and function on one side of the body; often caused by a spinal cord tumor or trauma to the spinal cord.

Carcinoma – A malignant growth of epithelial or gland cells; a synonymous term for cancer.
Carotid Artery – Large artery on either side of the neck that supplies most of the cerebral hemisphere with oxygenated blood.
Carotid Sinus – Slight enlargement of the common carotid artery; contains nerve cells sensitive to blood pressure. Stimulation of the carotid sinus can cause slowing of the heart, vasodilatation and a fall in blood pressure.
Carpal Tunnel – Space under a ligament in wrist through which the median nerve enters the palm of the hand.
CT Scan (Computed Tomography Scan) – A diagnostic imaging technique in which a computer reads X-rays to create a three-dimensional map of soft tissue or bone.
Catheter – A small tube used to inject dye to enable the view of blood vessels; also used to allow drainage of fluid or to provide access to body parts during surgery.
Cauda Equina – The bundle of spinal nerve roots arising from the end of the spinal cord and filling the lower part of the spinal canal.
Caudate Nucleus – Part of the basal ganglia, which are brain cells that lie deep in the brain.
Cerebellum – The lower part of the brain; located beneath the posterior portion of the cerebrum, that regulates unconscious coordination of movement.
Cerebrospinal Fluid – Water-like fluid that circulates around and protects the brain and spinal cord.
Cerebrum – The principal portion of the brain; occupies the major portion of the interior of the skull and controls conscious movement, sensation and thought.
Cervical – Of or relating to the neck.
Chiasm (Optic) – Crossing of visual fibers as they head toward the opposite side of the brain. For each optic nerve, most of the visual fibers cross to the opposite side, while some run directly backward on each side without crossing.
Chorea – A disorder, typically occurring in childhood, characterized by irregular, spasmodic involuntary movements of the limbs or facial muscles.
Choroid Plexus – A vascular structure in the ventricles of the brain where cerebrospinal fluid is produced.
Coccyx – The small bone at the end of the spinal column, formed by the fusion of four rudimentary vertebrae; also known as the "tail bone."
Coma – A state of unconsciousness from which one cannot be awakened; usually lasts more than six hours.
Computed Tomography (CT) Scan – A diagnostic imaging technique in which a computer reads X-rays to create a three-dimensional map of soft tissue or bone.
Concussion – An injury to the brain that results in temporary loss of normal brain function.
Contrast Medium – Any material (usually opaque to X-rays) employed to define a structure during a radiologic procedure.
Contusion – A bruise; cerebral contusions often involve blood vessels that leak into brain tissue.
Coronal Suture – The joint that connects the frontal bones and the parietal bones of the skull.
Cortex – The external layer of tissue covering the hemispheres of the cerebrum and cerebellum.
Cortical Area – A part of the brain generally defined by function (i.e. motor function or sensory function).
Cranium – The part of the skull that holds the brain.
Craniectomy – Surgical removal of a portion of the skull.
Craniopharyngioma – A benign tumor arising from the embryonic duct in the pituitary gland.
Cranioplasty – The operative repair of a defect or deformity of the skull.
Craniosynostosis – Premature closure of cranial sutures, limiting or distorting the growth of the skull.
Craniotomy – Opening of the skull, usually by removing a flap of bone to gain access to the brain.

Depressed Skull Fracture— A break in the bones of the head in which some bone is pushed inward, possibly pushing on or cutting into the brain.
Diabetes Insipidus Condition in which kidneys are unable to conserve water during the filtration of blood; urine is typically diluted.
Diffuse Axonal Injury – Damage to the axons of many nerve cells that lie in different parts of the brain; often a cause of unconsciousness after head trauma and brain injury.
Diffuse Brain Injury – Damage to the brain that can affect many parts of the brain; examples include diffuse axonal injury and inadequate blood flow.
Diphenylhydantoin – A medication used to control seizures; also known as phenytoin and Dilantin.
Diplopia – Double vision, usually due to weakness or paralysis of one or more of the extra ocular muscles.
Disc – Cartilaginous cushion found between the vertebrae of the spinal column; allows movement of the vertebrae; may bulge beyond the vertebral body and compress the nearby nerve root, causing pain and resulting in such conditions as a slipped disc, ruptured disc or herniated disc.
Dome – The round, balloon-like portion of the aneurysm that usually arises from the artery.
Doppler – A non-invasive study that uses sound waves to show the flow in a blood vessel; can be used to determine the degree of narrowing (percent stenosis) of the vessel.
Dura Mater – A tough fibrous membrane that covers the brain and spinal cord; the outermost layer of three membranes.
Dysesthesia – A condition in which an unpleasant and sometimes painful sensations are produced by ordinary touch, temperature or movement.
Dysphasia – Difficulty in the use of language due to a brain lesion.
Dystonia Musculorum Deformans – An affliction marked by muscular contractions producing distortions of the spine and hips.

Edema – An excessive accumulation of fluid; cerebral edema occurs in the in extracellular or intracellular areas of the brain.
Electroencephalopgraphy (EEG) – The study of the electrical activity in the brain. The record made is called an electroencephalogram.
Electromyography (EMG) – A method of recording the electrical currents generated in a muscle.
Endarterectomy – Removal of fatty or cholesterol plaques and calcified deposits from the internal wall of an artery.
Endocrine Gland – A gland that secretes products that usually have an effect on another organ.
Endocrinopathy – Any disease due to abnormality of quantity or quality in one or more of endocrine gland secretions.
Ependyma – The membrane lining the cerebral ventricles of the brain and central canal of the spinal cord.
Ependymoma – A growth in the brain or spinal cord arising from ependymal tissue.
Epidural – Form of local analgesia and anesthesia often injected into the outer section of the spinal canal.
Epidural Hematoma – A blood clot between the dura mater and the inside of the skull.
Epilepsy – Disorder characterized by repeated seizures caused by abnormal electrical discharges in the brain.

Falx (Cerebri) – An extension of dura mater between the right and left hemispheres of the brain.
Fontanelle – Normal openings in the skull of infants; the largest of these is the anterior fontanel or "soft spot" in the middle of the head.
Foraminotomy – Surgical opening or enlargement of the bony opening traversed by a nerve root as it leaves the spinal canal.
Fusiform Aneurysm – A spindle-shaped enlargement of a blood vessel.

Galactorrhea – The discharge of milk from the breasts unassociated with nursing or childbirth.
Gamma Knife – Equipment that precisely delivers a concentrated dose of radiation to a predetermined target using gamma rays.
Glasgow Coma Scale (GCS) – Neurological scale with which a patient's level of consciousness is determined; the most widely used system of classifying the severity of head injuries or other neurologic diseases
Glia – Cells that provide major support of brain cells, offering nutrition and maintenance to the nerve cells; also known as neuroglia.
Glioma – A tumor formed by glial cells.
Glioblastoma – A rapidly growing tumor composed of primitive glial cells, mainly arising from astrocytes.
Globus Pallidus – Part of the basal ganglia, which are brain cells that lie deep in the brain.

Hemangioma – An accumulation of multiple, dilated blood vessels in the skin.
Hematoma – A collection of blood outside the blood vessels; often characterized by a bruise
Hemianopia – Loss of vision of one-half of the visual field as a result of a stroke or brain injury; also known as hemianopsia.
HemiatrophyAtrophy of half of an organ or half of the body.
Hemiplegia – Paralysis of one side of the body.
Hemorrhage – Bleeding due to leaks from a blood vessel (internal) or through a cut or natural opening in the body (external).
Herniated Nucleus Pulposus (HNP) – Bulging of the central portion of an intervertebral disc through the outer cartilaginous ring; also known as a slipped disc or herniated disk. The material can compress the spinal cord or nerves in or exiting the spinal canal.
Hormone – A chemical substance formed in one gland or part of the body and carried by the blood to stimulate another organ's functional activity.
Hydrocephalus – A condition, often congenital, marked by abnormal and excessive accumulation of cerebrospinal fluid in the cerebral ventricles; results in dilated ventricles. In infants and young children, this condition often causes the head to enlarge.
Hydromyelia – Expansion of the spinal canal due to an accumulation of cerebrospinal fluid.
Hyperacusis – Abnormal sensitivity of hearing or auditory sensation.
Hyperesthesia – Excessive sensitivity to touch, pain or other stimuli.
Hypertension – High blood pressure.
Hypothalamus – A collection of specialized nerve cells at the base of the brain that controls the anterior and posterior pituitary secretions; is involved in other basic regulatory functions such as body temperature, hunger and thirst.

Infundibulum – A stalk extending from the base of the brain to the pituitary gland; also known as the pituitary stalk.
Intra-Aortic Balloon Counter Pulsation Device – A pump inserted into the main artery of the body, the aorta, to help the heart deliver blood to critical organs such as the brain and kidneys.
Intra-Arterial Catheterization Angiography – An invasive study in which a catheter (a small tube) is placed in the artery and contrast material is injected in order to make the blood vessels visible on an X-ray image. The catheter is inserted through the groin and into the femoral artery (the artery to the leg) through a needle and is guided into the arteries in the neck and head.
Intracerebral Hematoma – A blood clot within the brain.
Intracranial Pressure (ICP) – The overall pressure inside the skull.
Intraoperative Cisternography – Administration of a contrast dye into ventricles in the brain.
Ischemia – Inadequate circulation of blood generally due to a blockage of an artery, low glucose levels and other causes.

Jugular Veins – The major veins on each side of the neck carrying blood from the head towards the heart.

Labyrinth – The inner ear, comprising of the vestibule (the system that regulates physical balance) and cochlea (the portion that allows hearing).
Lamina – The flattened or arched part of the vertebral arch, forming the roof of the spinal canal.
Laminectomy – Complete removal of one or more laminae of the vertebrae.
Laminotomy – Partial removal of one or more of the lamina. (Click here to see "Laminotomy versus Laminectomy".)
Leptomeninges – Two thin layers of fine tissue covering the brain and spinal cord; consists of the pia mater and the arachnoid.
Leptomeningitis – Inflammation of the membranes covering the brain and spinal cord; commonly known as meningitis.
Leukodystrophy – Disturbance of the white matter of the brain; white matter is a component of the central nervous system and helps transmits signals through the regions of the brain.
Leukoencephalitis – An inflammation of the white matter of the brain.
Linear Accelerator – Equipment that uses X-rays to deliver a concentrated dose of radiation to a predetermined target.
Lipoma – A benign fatty tumor usually composed of mature fat cells.
Lordosis – An inward curvature of the spine.
Lumbar Drain – A device (usually a long, thin, flexible tube) inserted through the skin used to drain cerebrospinal fluid (CSF) from the lower back. The drainage procedure is performed to relieve pressure caused by excess CSF around the brain and spinal cord.

Magnetic Resonance Angiography (MRA) – A noninvasive study that is conducted in a Magnetic Resonance Imager (MRI). The magnetic images provide an image of the arteries in the head and neck.
Magnetic Resonance Imaging (MRI) – Diagnostic test that produces three-dimensional images of body structures using powerful magnets and computer technology.
Median Nerve – The nerve that runs through the muscles in the forearm and thumb and provides sensation to the hand. In carpel tunnel syndrome, the median nerve may be compressed or trapped at the wrist.
Medulloblastoma – Malignant brain tumor composed of medulloblasts, which are cells that develop in the fourth ventricle of the brain.
Meninges – The three membranes covering the spinal cord and brain — dura mater, arachnoid mater and pia mater.
Meningioma – A firm, often vascular, tumor arising from the coverings of the brain; the most common primary brain tumor.
Meningitis – An infection or inflammation of the membranes covering the brain and spinal cord.
Meningocele – A protrusion of the coverings of the spinal cord or brain through a defect in the skull or vertebral column; one form of spina bifida.
Meningoencephalocele – A protrusion of both the meninges and brain tissue through a skull defect; one form of spina bifida.
Myelin – The fat-like substance that surrounds the axon of nerve fibers and forms an insulating material.
Myelogram – An X-ray of the spinal canal following injection of a contrast material into the surrounding cerebrospinal fluid spaces.
Myelopathy – The study of disease behaviors in the spinal cord.
Myelomeningocele – A protrusion of the spinal cord and its coverings through a defect in the vertebral column.
Myopathy – Any disease of muscle.

Neuralgia – Pain that follows the path of a nerve due to nerve damage or irritation; causes include trauma and diabetes.
Neurectomy – Removal of a nerve or part of a nerve.
Neuritis – Inflammation of a nerve due to physical injury, infection and other causes.
Neuroblastoma – Malignant tumor arising from nerve tissue; commonly found in infants and children.
Neurofibroma – A benign tumor of the peripheral nerves due to an abnormal collection of fibrous and insulating cells.
Neurofibromatosis – A genetic condition characterized by numerous benign tumors affecting the organ system, nerves and other tissue.
Neurohypophysis – The posterior lobe of the pituitary gland.
Neurolysis – Removal of scar or reactive tissue from a nerve or nerve root.
Neuroma – A tumor or new growth largely made up of nerve fibers and connective tissue.
Neuropathy – Any functional or pathologic disturbance in the peripheral nervous system.
Nystagmus – Involuntary rapid movement of the eyes in the horizontal, vertical or rotary planes of the eyeball.

Occiput – The back part of the head.
Oligodendroglia – Non-nerve cells forming part of the supporting structure of the central nervous system.
Oligodendroglioma – A growth of new cells derived from the oligodendroglia.
Ophthalmoplegia – Paralysis of one or more of the eye muscles.
Osteoma – A benign tumor of bone.
Osteomyelitis – Inflammation of bone due to infection, which may be localized or generalized.

Papilledema – Swelling of the optic nerve head; can be seen in the back of the retina during an eye examination.
Paraplegia – Paralysis of the lower part of the body, including the legs.
Peritoneal Cavity – Body cavity in which the abdominal organs are situated.
Pituitary – Gland at base of the brain that secretes hormones into the blood stream. Those hormones then regulate other glands, including the thyroid, adrenals and gonads.
Polyneuritis – Inflammation of two or more nerves, simultaneously.
Porencephaly – Abnormal cavity within brain tissue, usually resulting from protrusion of a lateral ventricle.
Postical – State following a seizure, often characterized by altered function of the limbs and/or mentation.
Proprioception – Sensation concerning movements of joints and position of the body in space.
Pseudotumor Cerebri– Raised intracranial pressure, usually causing only headache and papilledema. No clear underlying structural abnormality.
Pupil – The black part of the eye through which light enters; enlarges in dim light and decreases in size in bright light.

Quadrantanopia – Defect in vision or blindness in one fourth of the visual field.
Quadriplegia – Paralysis of all four limbs; also known as tetraplegia

Rachischisis – Abnormal congenital opening of the vertebral column.
Radiation Oncologist – A medical doctor who has received advanced training in the treatment of persons receiving X-ray treatment for an illness.
Radiation Physicist – A person having a PhD degree who is trained in the science dealing with the properties, changes and interactions of continuous energy.
Radiologist – A medical doctor who has received specialized training in interpreting X-rays, CTs and MRIs, and performing angiography.
Radiotherapy – Treatment of a lesion with radiation.

Saccular Aneurysm – A balloon-like protrusion of a vessel (the more common type of aneurysm); also known as an intracranial berry aneurysm.
Scotoma – An area of decreased vision surrounded by an area of less depressed or normal vision.
Shunt – A tube or device implanted in the body to divert excess cerebrospinal fluid away from the brain to another place in the body. (Also see Valve.)
Spina Bifida – A congenital defect of the spine marked by the absence of a portion of the spine.
Spinal Fusion – Operative method of joining two or more vertebrae to treat such conditions as degenerative disc disease, scoliosis, spinal tumors and others.
Spondylolisthesis – Displacement of one vertebra onto another.
Spondylosis – Degenerative bone changes in the spine; usually marked at the vertebral joints.
Stenosis – Narrowing of a blood vessel.
Stereotactic Radiosurgery – The minimally-invasive delivery of radiation to a preselected, localized target; performed in treatment of benign and malignant tumors.
Strabismus – Deviation of eye movement which prevents the two eyes from moving in a parallel fashion.
Subarachnoid Hemorrhage – Bleeding into the space under the arachnoid membrane due to trauma or arupture of an aneurysm.
Subdural Hematoma – A collection of blood trapped under the dura mater, the outermost membrane surrounding the brain and spinal cord.
Syringomyelia – A condition in which a fluid-filled cavity or cyst forms in the spinal cord.

Teratoma – Tumor or growth made up of several different types of tissue (i.e. fat, bone, muscle, skin).
Thrombus – A blood clot attached to the wall of an artery.
Thalamus – A structure in the brain associated with transmitting sensory and motor signals; also controls sleep and attentiveness.
Transsphenoidal Approach – Operative method of reaching the pituitary gland or skull base traversing the nose and sinuses.
Trigeminal Neuralgia – Disorder that causes trigeminal nerve pain in the face; also known as tic douloureux.

Ultrasound – The use of high-frequency sound to create images of internal body structures.

Valve – Device placed in a shunt system to regulate the rate and direction of cerebrospinal fluid flow.
Vasoconstriction – A decrease in the diameter of blood vessels.
Vasodilatation – An increase in the diameter of blood vessels.
Vasopressin – A hormone secreted by the hypothalamus and stored in the posterior pituitary that raises blood pressure and increases reabsorption of water by the kidneys. The antidiuretic hormone (ADH), is formed in the hypothalamus and stored in the posterior pituitary gland. Its secretion reduces urine output.
Vasopressor – An agent which constricts the arteries and raises blood pressure.
Vasospasm – Spasm of blood vessels; leads to narrowing of the blood vessels.
Ventricle – The chambers within the brain that contain the cerebrospinal fluid.
Ventriculitis – Inflammation and/or infection of the ventricles.
Ventriculogram – An X-ray study of the ventricles.
Ventriculostomy – A procedure in which a hole is created in the cerebral ventricle to drain cerebrospinal fluid or blood from the central nervous system; a means to relieve pressure from the brain and spinal cord.
Ventricular Drainage – Insertion of a small tube into the ventricles to drain cerebrospinal fluid; performed to relieve pressure caused by excess CSF around the brain and spinal cord.
Vermis – Middle part of the cerebellum between the two hemispheres; plays a part in body posture and motion.
Vertebra – Any of the 33 bones of the spinal column.
Vertigo – An abnormal sensation of rotation or movement of one's self or the environment.

X-ray – Application of electromagnetic radiation to produce a film or picture of a bone or soft-tissue area of the body.

The AANS does not endorse any treatments, procedures, products or physicians referenced in these patient fact sheets. This information is provided as an educational service and is not intended to serve as medical advice. Anyone seeking specific neurosurgical advice or assistance should consult his or her neurosurgeon, or locate one in your area through the AANS’ Find a Board-certified Neurosurgeon” online tool.

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