Acoustic neuroma: A benign tumor of the hearing nerve (eighth cranial nerve), also called vestibular schwannomas. More about acoustic neuromas.
Adenoma: A benign growth formed of glandular tissue.
Allograft: A graft of bone or tissue between individuals of the same species. Allografts are usually obtained from cadavers.
Aneurysm: An abnormal bulging or stretching of a weakened wall of a blood vessel. More about aneurysms.
Angiography (arteriography): Imaging of blood vessels using injected contrast material (dye) to better visualize the vessels. The word is derived from angio (blood vessels) and gram (record or picture).
Angioplasty: The reconstitution or recanalization of a blood vessel. Angioplasty may involve balloon dilation, the mechanical stripping of intima (innermost layer of an artery), forceful injection of a thrombolytic (clot-busting) agent, or the placement of a stent (vessel prosthesis).
Annulus: The tough outer ring of a spinal disk.
Anticoagulant: A medication that prevents coagulation of the blood.
Aphasia: Difficulty with language, or the loss of use of language, in reading, writing, or speaking. This failure to understand the written, printed, or spoken word is not related to intelligence, but to specific lesions in the brain.
Arachnoid: The middle of three membranes that cover and protect the brain and spinal cord. More about arachnoid cysts and sub-arachnoid hemorrhage.
Arachnoiditis: Inflammation of the arachnoid membrane, most commonly seen within the spinal cord around the spinal cord and cauda equina.
Arteriosclerosis: A thickening and calcification of the arterial wall with loss of elasticity and contractility.
Arteriovenous: Relating to both arteries and veins.
Arteriovenous malformation (AVM): A collection of blood vessels with one or more abnormal communications between arteries and veins, which may cause hemorrhage or seizures. More about AVMs.
Arthrodesis: The surgical fixation or fusion of a joint.
Astrocytoma: A tumor within the substance of the brain or spinal cord made up of astrocytes, often classified from grade I (slow-growing) to grade III (rapidly growing). More about brain tumors in adults or brain tumors in children.
Ataxia: The loss of muscular coordination, abnormal clumsiness.
Atherosclerosis: Arteriosclerosis (see above) characterized by irregularly distributed lipid deposits in the arteries
Atrophy: A wasting of the tissues of a body part.
Autograft: A graft of bone obtained from a patient for transplantation elsewhere on the same patient.
