Preserved cutaneous silent period in cervical root avulsion

Abstract

Objective: Brachial plexus injuries are usually severe and involve the entire brachial plexus, sometimes occurring with root avulsions. Imaging and electrodiagnostic studies are an essential part of the lesion evaluation; however, the results sometimes show a discrepancy. The cutaneous silent period (SP) is a spinal inhibitory reflex mediated by small-diameter A-delta nociceptive fibers. The aim of the study was to determine if cutaneous SP testing may serve as a useful aid in evaluation of brachial plexus injury and/or in the diagnosis of root avulsion. Methods: In 19 patients with traumatic brachial plexus injury (15 males, age 18-62 years) we performed a clinical examination, CT myelography and neurophysiological testing. A needle EMG was obtained from muscles supplied by C5-T1 myotomes. Cutaneous SP was recorded after painful stimuli were delivered to the thumb (C6 dermatome), middle (C7) and little (C8) fingers while subjects maintained voluntary contraction of intrinsic hand muscles. Results: Electrodiagnostic and imaging studies confirmed root avulsion (partial or total) maximally involving C5, C6 roots in 12 patients, whereas only in 4 of them the cutaneous SP was partially absent. In the remaining subjects, the cutaneous SP was preserved. Conclusion: In brachial plexopathy even with plurisegmental root avulsion, the cutaneous SP was mostly preserved. This method cannot be recommended as a reliable test for diagnosis of single root avulsion; however, it can provide a quick physiological confirmation of functional afferent A-delta fibers through damaged roots and/or trunks. The clinicians may add this test to the diagnosis of spinal cord dysfunction.

Transplantation of Cultured Olfactory Bulb Cells Prevents Abnormal Sensory Responses during Recovery from Dorsal Root Avulsion in the Rat

“…The resulting vascular and cellular destruction of the dorsal horn at the cervical level was similar to that shown by others who avulsed roots at the lumbar level 38-40 . Importantly, the extent and location of damage to the dorsal horn along at least two segments of the cervical spinal cord were also similar to that seen in imaging studies of patients with brachial plexus injuries 41,42 . We did not examine the response of the adjacent, uninjured C6 or T1 dorsal roots and their afferent input to the dorsal horn above or below the injured segments.…”