MAGNETIC STIMULATION OF BICEPS AFTER INTERCOSTAL CROSS-INNERVATION FOR BRACHIAL-PLEXUS PALSY - A STUDY OF MOTOR EVOKED-POTENTIALS IN 25 PATIENTS

We studied the motor evoked potentials (MEP) in the biceps of 25 patie nts with traumatic brachial plexus palsy from root avulsion after cros s-innervation by intercostal nerves. We used transcranial, transcervic al and transthoracic magnetic stimulation at 8 to 235 months (mean 51) after transfer of intercostal nerves to the musculocutaneous nerve. B iceps strength recovered to MRC grade 2 in eight patients, grade 3 in three and grade 4 in 14. The mean latency of the MEP in the normal bic eps on transcranial stimulation was 12.5 +/- 1.3 ms and on transcervic al stimulation 6.3 +/- 1.1 ms. After intercostal reinnervation the mea n latency on transcranial stimulation was 21.7 +/- 4.5 ms and on trans thoracic stimulation 11.6 +/- 3.8 ms. The latency of the biceps MEP af ter reinnervation by intercostal nerves on transcranial and transthora cic magnetic stimulation correlated well with the duration of follow-u p and the latency of the MEP on transthoracic magnetic stimulation cor related significantly with muscle power.