title: Preserved cutaneous silent period in cervical root avulsion.
abstract: 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.
  
  
  
  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.
  
  
  
  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.
  
  
  
  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.
authors: a Department of Neurology , Third Faculty of Medicine, Charles University , Prague , Czech Republic.
authors: Peter
authors: P
authors: Vasko
authors: a Department of Neurology , Third Faculty of Medicine, Charles University , Prague , Czech Republic.
authors: Vaclav
authors: V
authors: Bocek
authors: b Department of Neurosurgery , Third Faculty of Medicine, Charles University , Prague , Czech Republic.
authors: Libor
authors: L
authors: Mencl
authors: b Department of Neurosurgery , Third Faculty of Medicine, Charles University , Prague , Czech Republic.
authors: Pavel
authors: P
authors: Haninec
authors: a Department of Neurology , Third Faculty of Medicine, Charles University , Prague , Czech Republic.
authors: Ivana
authors: I
authors: Stetkarova
mesh_terms: D000293:Adolescent; D000328:Adult; D001917:Brachial Plexus / Q000293:injuries; D020516:Brachial Plexus Neuropathies / Q000150:complications* / Q000175:diagnosis; D004576:Electromyography / Q000379:methods; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction; D011843:Radiculopathy / Q000175:diagnosis* / Q000209:etiology; D011930:Reaction Time; D012018:Reflex
keywords: A-delta fibers; Brachial plexopathy; Cutaneous silent period; Electromyography; Root avulsion