Robert G. Ojemann, Saul Aronow and William H. Sweet
Part 2: Clinical applications
James B. Macon, Charles E. Poletti, William H. Sweet, Robert G. Ojemann and Nicholas T. Zervas
✓ In 27 patients undergoing laminectomy, spinal cord function was monitored by epidural bipolar recordings of conducted spinal somatosensory evoked potentials (SEP's) across the laminectomy site, with calculation of spinal conduction velocity (CV). In control cases without myelopathy, the CV remained relatively constant (± 3%) even during prolonged operations, despite markedly changing levels of anesthesia. Acute CV changes were detected intraoperatively in three cases: these patients displayed improvement after extramedullary (Case 1) and intramedullary decompression (Case 2), and deterioration after direct unilateral dorsal column injury (Case 3). These intraoperative CV alterations correlated postoperatively with changes in the neurological examination. Although a unilateral lesion confined to the dorsal column abolished the ipsilateral SEP in Case 3, complete anterior quadrant lesions did not consistently change the CV (Case 4). This further suggests that the SEP is generated entirely by ipsilateral dorsal column activation. Accurate measurement of this dorsal column conduction velocity across the operative field provides a very sensitive means of monitoring spinal cord function during operations for neurosurgical spinal lesions.
Charles E. Poletti, Alfred M. Cohen, Donald P. Todd, Robert G. Ojemann, William H. Sweet and Nicholas T. Zervas
✓ Clinical trials for abatement of intractable pelvic cancer pain were conducted in two patients, each electing surgical implantation of one of two indwelling catheter systems for administration of morphine into the spinal epidural space. Both systems, one consisting of a partially indwelling Broviac catheter, and the other, completely indwelling, consisting of a morphine reservoir connected to a shunt pump and on-off Hakim valve assembly, permitted the patients to return home where they could self-administer epidural morphine. Each patient reported that 2 mg of epidural morphine provided 8 to 12 hours of pain relief at a level superior to their previous systemic narcotic medication. On a regimen of 2 mg of epidural morphine administered twice daily, both patients experienced analgesia for 6 months, unaccompanied by alterations in sensory, motor, or cognitive functioning, and with little drug tolerance reaction.