Extensor carpi radialis recovery predicted by qualitative SEP and clinical examination in quadriplegia

This prospective study examined the efficacy of the qualitative somatosensory evoked potential (SEP) and the initial clinical neurologic evaluation to predict motor power recovery of the extensor carpi radialis muscle (ECR). Twenty three C5-6 Frankel A-D spinal cord injured (SCI) subjects had SEPs of the median nerve (MN) and superficial radial nerve (SRN) performed within 72 hours to one week post injury. The MN and SRN cortical SEPs were qualitatively graded as either present or absent. Fifteen subjects whose initial ECR muscle strength was less than or equal to 3/5 and eight subjects whose muscle strength was greater than 3/5 were followed up to 12 to 18 months post injury for improvement in ECR muscle strength. The subject's ECR strength was evaluated by manual muscle testing (MMT) at 72 hours, weekly for three weeks, monthly for three months, and then at six, 12, and 18 months. The pin sensation at the C-5 dermatome was also tested at the above intervals and graded as either present or absent. A one tail Fisher Exact test compared the presence or absence of the MN and SRN SEPs to the recovery of the ECR to 3/5. The same one tail test also compared the presence or absence of the 72 hour C-5 pin sensation and the 72 hour MMT to the ECR recovery. Among the 15 subjects with an initial MMT of less than or equal to 3/5, ten subjects had successful ECR recovery (greater than 3/5); 5 did not. The C-5 pin sensation correctly predicted ECR recovery in all subjects studied (p less than 0.001).