Arachnoidal diverticula and cystlike dilatations of the nerve-root sheaths in lumbar myelography.

Diverticulum-like widening of one or several nerve-root sheaths was found in 24 of 136 patients examined by lumbar myelography. No clinical significance of the diverticula was demonstrated. The roots most commonly affected were the S 1 and S 2 roots, carrying approximately 60 per cent of the diverticula. A system of classification according to morphology and to size compared with the root involved is proposed. A relationship between magasac and arachnoidal diverticula is confirmed.