Papilledema:  Swelling of the optic nerve head, can be seen in the back of the retina during eye examination.
Paraplegia:  Paralysis of the lower part of the body including the legs. More about spinal cord injury.
Paresthesia:  Numbness, tingling, or a "pins and needles" feeling.
Pars interarticularis:  The area between the upper and lower articulating (joining) facets of two vertebrae.
Pedicle:  One of the two short stems of bone that project outward from the body of each vertebra.
Peripheral nervous system:  The peripheral part of the nervous system external to the brain and spinal cord from their roots to their peripheral terminations.
Pituitary:  The gland at base of the brain that secretes hormones into the bloodstream. Those hormones then regulate other glands including the thyroid, adrenals, and gonads. The "master gland." More about our pituitary surgery program.
Polyneuritis:  Inflammation of two or more nerves simultaneously.
Posterior fossa:  A hollow depression in the back of the skull in which the cerebellum and several other structures are located.
Pre-ictal:  Preceding a seizure (see ictal).
Proprioception:  Sensation concerning movements of joints and position of the body in space.
Pseudarthrosis:  Failure of fusion to achieve proper union of vertebrae.
Pseudomeningocele:  A collection of cerebrospinal fluid that is due to a dural leak after spine surgery, not a congenital disorder.
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.

Weill Cornell Medicine Brain & Spine Center 525 East 68 Street, Box 99 New York, NY 10065 Phone: 866-426-7787