2001 OITE Question 171

Question

Where are the sacral roots located within the canal at the L1-2 disk level?

1- random pattern

2- anterior

3- central

4- lateral

5- posterior

Figures

Answer (click for answer)

Preferred response: 3

At the level of the first and second lumbar vertebrae, the roots of the first through the fifth lumbar nerves overlap the terminal portion of the spinal cord. The dorsal and ventral roots of the first through the fifth lumbar nerves have come together and form organized dorsoventral layers. The dorsal and ventral roots of the first sacral nerves remain slightly separated at this level. The more caudad sacral roots encircle the terminal cord. An intricate web of arachnoid membrane holds the nerve roots in a fixed relationship to each other.

Reference: Wall EJ, Cohen MS, Abitbol JJ, Garfin SR: Organization of intrathecal nerve roots at the level of the conus medularis. JBJS Am 1990; 72: 1495-1499.