The role of somatosensory evoked potentials in the evaluation of spinal cord retethering

Early detection of clinically significant spinal cord retethering is of paramount importance for the preservation of neurologic function in patients with repaired spinal dysraphic lesions. We retrospectively analyzed 90 children who were followed with serial peroneal somatosensory evoked potentials (SEPs) after a repair of their spinal dysraphic lesions with the objective of evaluating whether SEPs were a useful way of monitoring these children to facilitate early detection of clinically significant retethering. Three hundred and nine studies were performed on these children yielding a mean of 3.4 studies per patient, The median time between SEP studies was 13 months. A clinical examination was performed at the time each SEP was done, Sixty-one patients (68%) had a myelomeningocele; 25 (28%) had a lipomyelomeningocele while other types of dysraphic lesions were found in the remaining 4%. Nineteen patients (21%) had no change in serial SEPs; 7 of these 19 (37%) had a deterioration in clinical status while the SEPs were stable. Twenty-six patients (29%) showed improvement in serial SEPs, however, 3 of the 26 had clinical worsening at the time the SEPs improved. SEPs deteriorated in 45 patients (50%); 13 of the 45 had an associated clinical deterioration, and the remaining 32 were stable clinically. Twenty-three patients (26%) had a clinical deterioration; of these only 13 had a corresponding deterioration in SEPs, 7 patients had stable SEPs while 3 had improvement in SEPs at the time of clinical deterioration. This results in a false-positive rate of 71% and a false-negative rate of 43%. We conclude that serial SEPs do not correlate well with clinical status and are not a useful modality for monitoring patients at risk for retethering.