Glossary

End Vertebra - i. The most cephalad (i.e. toward the head) vertebra of a curve, whose superior surface tilts maximally toward the concavity of the curve. ii. The most caudad (i.e. toward the coccyx) vertebra whose inferior surface tilts maximally toward the concavity of the curve.

Endogenous - Arising within or derived from the body.

Endoscope - A medical device for viewing internal portions of the body. It is usually comprised of fiber optic tubes and video display instruments.

Endoscopy - Inspection of internal body structures or cavities using an endoscope.

Epidural - Situated outside the thin, tough dural membrane that surrounds the brain and spinal cord.

Epidural membrane - See peridural membrane.

Excision - Removal by cutting away material.

Exogenous - Originating outside of the body.

Extra-foraminal zone - The zone beyond the sagittal plane of the lateral edges of the pedicles, having no well-defined lateral border. Syn: far lateral zone, far-out zone.

Extra-ligamentous - Posterior or lateral to the posterior longitudinal ligament. Note: Extra-ligamentous disc refers to displaced disc tissue that is located lateral, or posterior to the posterior longitudinal ligament. If the disc has extruded through the posterior longitudinal ligament it is sometimes called "trans-ligamentous" or "perforated," and if through the peridural membrane, it is sometimes refined to as "trans-membranous."

Extruded disc - A herniated disc in which, in at least one plane, any one distance between the edges of the disc material beyond the disc space is greater than the distance between the edges of the base in the same plane, or when no continuity exists between the disc material beyond the disc space and that within the disc space.