Cutaneous silent periods in the assessment of mild cervical spondylotic myelopathy.
METHODS
Clinical, neuroradiologic, and neurophysiologic description of 21 patients with compressive cervical spondylotic myelopathy (CCSM).


OBJECTIVE
To describe the utility of cutaneous silent periods (CSPs) for functional evaluation of mild CCSM.


BACKGROUND
Electroneurography, electromyography, and somatosensory and motor evoked potentials (SEPs, MEPs) are routinely used for comprehensive functional neurophysiological evaluation of CCSM. CSPs have been reported in various intramedullary spinal cord lesions, however, they have not been systematically studied in mild CCSM.


METHODS
We investigated 21 patients with multilevel CCSM as documented by magnetic resonance imaging. We recorded CSPs in thenar muscles after noxious digit II stimulation and compared them with median and tibial nerve SEPs and MEPs obtained from abductor digiti minimi and tibialis anterior muscles. Electroneurography and electromyography were obtained in affected myotomes.


RESULTS
CSP onset and end latencies were delayed, and CSP duration was shortened, in CCSM patients. CSP abnormalities were present in 17 patients of whom all, but 1 presented with intramedullary magnetic resonance imaging hyperintensity. All 11 limbs affected by hypalgesia and thermhypesthesia had abnormal CSPs, whereas no spinothalamic deficit was noted in any limb with normal CSPs. CSP onset latency was inversely correlated with JOA score and N13 amplitude, and was positively correlated with central motor conduction time to abductor digiti minimi. CSP duration was inversely correlated with central motor conduction time to tibialis anterior. Electromyographic abnormalities were found in 7 patients.


CONCLUSIONS
We confirm the value of neurophysiological evaluation of CCSM. MEPs were more frequently abnormal than SEPs. CSP abnormalities were almost equally sensitive as upper limb MEPs, and were highly associated with spinothalamic dysfunction. The high correlation of CSP abnormalities with corticospinal tract dysfunction suggests supraspinal influence on CSPs. Our findings corroborate the utility of CSP testing in the comprehensive assessment of intramedullary spinal cord dysfunction in CCSM.
Stetkarova
Ivana
I
Department of Neurology, Na Homolce Hospital, Roentgenova 2, Prague 5, Czech Republic. ivana.stetkarova@homolka.cz
Kofler
Markus
M
D000328:Adult; D000368:Aged; D016022:Case-Control Studies; D002574:Cervical Vertebrae; D004576:Electromyography; D019054:Evoked Potentials, Motor / Q000502:physiology*; D005073:Evoked Potentials, Somatosensory / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D008475:Median Nerve / Q000503:physiopathology; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000294:innervation*; D009424:Nervous System Physiological Phenomena; D009431:Neural Conduction / Q000502:physiology*; D013118:Spinal Cord Diseases / Q000503:physiopathology*; D013130:Spinal Stenosis / Q000503:physiopathology*; D055009:Spondylosis / Q000503:physiopathology*; D013979:Tibial Nerve / Q000503:physiopathology