Spinal tap: See lumbar puncture
Spinous process: A bony prominence projecting backward from a vertebra that can be felt under the skin on one's back.
Spondylolisthesis: Forward displacement or slippage (subluxation) of one vertebra over another. More about spondylolisthesis.
Spondylosis: Degenerative bone changes in the spine usually most marked at the vertebral joints with bony spur formation. More about ankylosing spondylosis.
Stenosis: Narrowing of the openings of the foramen and/or the spinal canal; narrowing of a blood vessel. More about spinal stenosis.
Stent: An endovascular prosthetic device, usually an open mesh cylinder, placed within a blood vessel to provide the support to keep that vessel open.
Stereotactic surgery: Surgical technique whereby the exact target (i.e., tumor, lesion, AVM) is calculated three-dimensionally utilizing CT or MRI and computer. From stereo (three-dimensional) and tactic (touch).
Subarachnoid: Located under the arachnoid membrane and above the pia mater.
Subarachnoid hemorrhage: Blood in, or bleeding into, the space under the arachnoid membrane, most commonly from trauma or from rupture of an aneurysm. More about subarachnoid hemorrhage.
Subdural: Located below the dura mater and above the arachnoid meninges.
Subdural hematoma: A collection of blood (clot) trapped under the dura matter, the outermost membrane surrounding the brain and spinal cord.
Suprascapular nerve: The nerve that originates from the superior trunk of the brachial plexus. It supplies the shoulder joint and deep shoulder structures.
Syringomyelia (syrinx): A fluid-filled cavity in the spinal cord, often occurring with Chiari malformation. More about Chiari malformation.
Teratoma: Tumor or growth made up of several different types of tissue (fat, bone, muscle, skin).
Thalamus: Brain cells that lie in the upper part of the brainstem.
Thrombolytic agent: A clot-busting" drug; such agents may be administered into veins or arteries.
Thrombus: A blood clot attached to the wall of an artery.
Tic douloureux: See trigeminal neuralgia.
Torticollis: The spasmodic contraction of neck muscles drawing the head to one side with the chin pointing to the other side. More about movement disorders.
Transsphenoidal approach: Operative method of reaching the pituitary gland or skull base traversing the nose and sinuses. More about pituitary surgery.
