Facet:  A small, smooth-surfaced end of a bony projection (articular process) that functions as part of a joint.
Facet joint:  Each of four joints formed above, below, and on either side of a vertebra. The lower bony projection of one vertebra meets the upper projections of the vertebra below it, forming facet joints.
Facetectomy:  Surgical removal of one of the facets; excision of a facet joint.
Falx cerebri:  An extension of dura between the right and left hemispheres of the brain.
Fontanelle:  Normal openings in the skull of infants. The largest of these is the anterior fontanelle, the "soft spot" in the middle of the head. More about craniofacial anomalies.
Foramen:  A hole or opening that acts as a passageway for nerves or blood vessels.
Foraminotomy:  Surgical enlargement of the foramen/foramina.
Fractionated therapy:  Stereotactic radiation that is given in multiple lower-dose treatments rather than in a single session. More about our Stereotactic Radiotherapy Program
Fusiform aneurysm:  A sausage-like enlargement of the blood vessel.

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