Sensory disturbance following percutaneous retrogasserian glycerol rhizotomy

Nineteen patients with tic douloureux were treated with glycerol injection in the trigeminal cistern. Facial sensibility was measured with an electrical stimulator one day before and one day after the glycerol treatment. The thresholds for perception and pain, and the maximal pain tolerance rose by about 50% (p less than 0.01, 0.01, and 0.001, respectively). The hypaesthesia and hypalgesia were most marked just below the eye, whereas the mandibular division showed only slight sensory impairment. In 13 patients a follow-up sensimetry study was done 1-7 months after surgery. Thirteen patients became completely free of pain and one almost completely free from pain (74%). Two had no pain relief. Twelve patients had no subjective complaints of the treatment. Three reported on dysaesthesiae (16%) over the previously painful area. Seven patients (37%) had subjective sensations of diminished or altered sensibility: numbness and hypalgesia in the face. Corneal hypaesthesia was recorded in ten patients (53%). Glycerol has a non-specific neurotoxic effect which is equal for tactile and nociceptive fibres. Sensory impairment may be a conditio sine qua non for a good clinical result.