[Spinal anesthesia for a patient with long-term SMON]

SMON (subacute myelo-optico-neuropathy) may result from clioquinol neurotoxicity. An 81-year-old woman underwent internal fixation for left intertrochanteric fracture. She had been diagnosed as having SMON twenty years previously. Sensory examination revealed paresthesia and decreased deep sensation in the lower extremity. A recent neuropathological report shows that in long-term SMON of about fifteen years, degeneration is located from the medulla oblongata to T5-6. We performed spinal anesthesia of which the level of analgesia was below T5-6 in the present case. The level of anesthesia was determined by the pinprick test, and was recognized as below T10. Postoperatively, both the sensory level of analgesia and vital signs remained stable. There was no worsening of neurological findings after spinal anesthesia, including the postoperative period. In conclusion, spinal anesthesia which was limited to below the level of degeneration could be applied in a case of long-term SMON.