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.
Coronal suture:  The line of junction of the frontal bones and the parietal bones of the skull. More about craniofacial anatomy.
Corpectomy:  Removal of the body of a vertebra. The body is the solid bony mass, almost circular in appearance, that forms the front part of each vertebra.
Corpus callosum:  The fibrous band connecting the hemispheres of the brain.
Cortex:  The external layer of gray matter covering the hemispheres of the cerebrum and cerebellum.
Craniectomy:  Surgical removal of a portion of the skull.
Craniopharyngioma:  A congenital tumor arising from the embryonic duct between the brain and pharynx. More about craniopharyngiomas.
Cranioplasty:  The operative repair of a defect of the skull.

 Premature closure of cranial sutures, limiting or distorting the growth of the skull. More about craniosynostosis and other craniofacial anomalies.

Craniotomy:  Surgical opening of the skull, usually by creating a flap of bone.
Cranium:  The part of the skull that holds the brain.
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.
Diphenylhydantoin:  Dilantin; a medication used to control seizures. More about epilepsy in adults and epilepsy in children.

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