Somatosensory evoked potential, neurological examination and magnetic resonance imaging for assessment of cervical spinal cord decompression

The present study was designed to determine the relationship between neurol ogical testing, anatomical imaging, and electrophysiological monitoring for assessing outcome of cervical spinal cord decompression. We prospectively studied 28 consecutive patients (age 39-76 yr) who were subjected to presur gical-(1-3 wk) and postsurgical (3-4 mo) neurological examination and recor ding of the median nerve somatosensory evoked potential (SEP). In 13 patien ts, magnetic resonance imaging (MRI) was also performed. Changes in neurolo gical function, SEP and MRI were evaluated and graded as (1) improvement,(2 ) no change or (3) deterioration. Neurological outcome (NO) was based on ch anges in motor grade strength, sensory, reflexes and gait. The SEP outcome was based on changes in latency and disappearance of SEP waveform component s whereas MRT evaluation was based on changes in spinal cord and canal diam eters. Significance of association between NO, SEP and MRI was determined b y Pearson's Chi-Square statistic (P<.05). The SEP improved in 71% (20/28) a nd deteriorated in 28% (8/28) of the subjects. An association between SEP c hanges and NO was found in 82% (23/28) of the subjects (P=.0038). Decompres sion increased the spinal canal diameter in 92% (12/13), and the spinal cor d diameter in 38% (5/13) of the subjects. An association between NO, or SEP and MRI was not detected. Changes in median nerve SEP latency appear to be predictive of the neurological status of patients subjected to cervical sp inal cord decompression. Postoperative increments in SEP latency or disappe arance of the SEP waves were indicative of poor outcome after surgical deco mpression of the cervical spinal cord.