Carcinoma:  Cancer; a malignant growth of epithelial or gland cells.
Carotid artery:  The large artery on either side of the neck that supplies most of the blood to the brain.
Carotid cavernous fistula (CCF):  An abnormal communication between the internal and external portions of the carotid arteries or any of their branches and the cavernous sinus.
Carotid sinus:  Slight dilatation on the common carotid artery at its bifurcation containing nerve cells sensitive to blood pressure. Stimulation can cause slowing of the heart, vasodilatation, and a fall in blood pressure.
Catheter:  A small tube used to inject a dye to see the blood vessels, similar to that used for looking at vessels in the heart.
Cauda equina (CES):  The bundle of long spinal nerve roots arising from the end of the spinal cord and filling the lower part of the spinal canal (from approximately the thoracolumbar junction down). These long nerves resemble a horse's tail (cauda equina).
Cavernous malformation (cav mal):  A rare type of vascular malformation. More on cavernous malformations.
Central nervous system (CNS):  The brain and the spinal cord.
Cerebellum:  The lower part of the brain, which is beneath the posterior portion of the cerebrum and regulates unconscious coordination of movement.
Cerebrospinal fluid (CSF):  A clear, water-like fluid that circulates around the brain and spinal cord.
Cerebrum:  The principal portion of the brain, which occupies the major portion of the interior of the skull and controls conscious movement, sensation, and thought. Separated into right and left hemispheres.
Cervical spine:  The upper spine/neck; the cervical spine is made up of seven vertebrae.
Chiari malformation:  The downward (caudal) displacement of part of the cerebellum or brainstem below the foramen magnum. May also have/cause hydrocephalus, cord symptoms. More about Chiari malformation.
Chorea:  A disorder, usually of childhood, characterized by irregular, spasmodic involuntary movements of the limbs or facial muscles. More about spasticity.
Choroid plexus:  A vascular structure in the ventricles of the brain that produces cerebrospinal fluid.
Coccyx:  The small bone at the end of the spinal column, formed by the fusion of four rudimentary vertebrae (commonly called the "tail bone").
Coma:  A state of profound unconsciousness from which one cannot be roused.
Computerized tomography (CT) scan:  A diagnostic imaging technique that rapidly x-rays the body in cross-sections, or slices. A computer pieces together the x-rays to create a three-dimensional map of soft tissue or bone.
Concussion:  A disruption, usually temporary, of neurological function resulting from a blow or violent shaking. More about concussion.
Contrast medium (dye):  Any material (usually opaque to x-rays) employed to delineate or define a structure during a radiologic procedure.

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