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This study shows that there is a relationship between simple meningocele and the tethered cord syndrome. Two groups of patients were examined: the first comprised patients presenting with neurological abnormality at some period after initial closure of a simple meningocele, and the second group (18 patients) had elective myelography after closure of a simple meningocele in the neonatal period (in 17 of the 18 cases). Of these 18 cases. 10 showed an intradural abnormality, and all underwent surgery confirming their myelographic diagnosis. The conclusion is drawn that after closure of a simple meningocele in the neonatal period, patients should have elective myelography in the first 12 months of life to determine whether or not the tethered cord syndrome is likely to develop during the period of growth.

The effects of increasing concentrations of halothane on the morphology of spinal somatosensory evoked potentials (SEP) were studied in seven anaesthetized sheep. Anaesthesia was induced with thiopentone and maintained with nitrous oxide in oxygen. Ventilation was controlled throughout. Arterial pressure, temperature and end-tidal carbon dioxide tension were monitored. A lumbar laminectomy was performed, the sciatic nerve exposed and a baseline spinal SEP was recorded from the surface of the lumbar spinal cord. Halothane was introduced in incremental steps of 1% up to 3% and further SEP were recorded. These recordings revealed that the spinal SEP peak latencies and general waveform configuration were stable under halothane anaesthesia. Baseline SEP amplitude was similar to that obtained with 1% halothane; however, at concentrations of 2% halothane or greater, there was a significant (P less than 0.005) attenuation of all components of the spinal SEP. These findings have important anaesthetic implications for patients undergoing spinal cord monitoring using SEP, although interspecies differences may occur.