FIG 2. Electrophysiologic and MR changes in L5 nerve root lesion.

A, Axial T1-weighted image localizes affected muscles. No abnormalities are evident.

B,Axial TIRM image reveals a signal intensity increase in the TA, ED, PL, TP, and popliteus (P) muscles. This pattern was consistent with an L5 nerve root lesion.

C, EMG shows spontaneous activity in the TA, extensor hallucis longus (EHL), and TP muscles; as with MR results, these findings are consistent with a lesion of the L5 root.

D, Nerve conduction studies of the peroneal nerve show normal CMAP after stimulation of the peroneal nerve, at the level of the ankle, distal and proximal to the fibular head (amplitude, 9 mV; nerve conduction velocity, 50 m/s). In this patient, a lumbar disk herniation was confirmed at surgery.