The short latency muscle reflex in the diagnosis of disc disease affecting roots L4 and L5.

A segmental monosynaptic reflex that can be evoked by using voluntary muscle contraction to facilitate it is of use in diagnosis. In a group of 15 healthy volunteers the reflex response from tibialis anterior proved to be 31.08 +/- 2.48 msec with a side difference of 0.41 +/- 0.36 msec and from peroneus longus 29.90 +/- 2.20 msec with a side difference of 0.38 +/- 0.25 msec. Of 21 patients with radiologically proven disc herniation (of root L4 in 5 and of root L5 in 16) 16 showed a delay of more than 2.5 SD of the side difference or no response at all. It is hope that this simple and speedy method will be routinely adopted as complement to standard electromyography.