MICROSURGICAL ANATOMY OF THE DORSAL CERVICAL NERVE ROOTS AND THE CERVICAL DORSAL-ROOT GANGLION VENTRAL ROOT COMPLEXES

BACKGROUND It is known that a ''dissociated motor loss'' of the deltoi d muscle can occur with disconcerting frequency after cervical spine s urgery. The etiology of this entity is in question. We conducted an an atomic study to identify anatomic factors that might predispose C5 to injury. METHODS We studied 128 dorsal cervical nerves and root ganglio n/ventral root complexes in 10 adult cadavers. At each cervical level the following data were recorded: number of rootlets, range of width o f rootlets, length of DREZ, cranial angles of the superior and inferio r rootlets with the spinal cord, length of the superior and inferior r ootlets, dimensions of the foramina, dimensions of the dorsal root, di mensions of the dorsal root ganglion (DRG)/ventral root (VR) complex, and the blood supply to the DRG. The histology at the site of compress ion was also examined. Statistical analysis was conducted using the si ngle factor-repeated measures analysis of variance. RESULTS We found t hat, 1) the C5 superior dorsal rootlets angle less inferiorly from the cervical cord than the other dorsal cervical roots (p = 0.001), 2) th e majority of the DRG/VR complexes from C3 to C6 were compressed by th e vertebral artery (73%), 3) the C5 DRG/VR complex was compressed to t he greatest extent (77.6%, p = 0.3519), and 4) the ganglionic artery w as more frequent at C4, C5, and C6. CONCLUSION To our knowledge, the s econd finding has not been reported previously. The first and third fi ndings may help explain why C5 is more vulnerable to injury. (C) 1998 by Elsevier Science Inc.