Negative Exploration during Microvascular Decompression

INTRODUCTION: Microvascular decompression (MVD) has been shown to be effective for trigeminal neuralgia (TN). Although patient selection criteria and outcome have been described in detail, there are few reports in the literature focusing on options when the exploration is negative for vascular compression of the trigeminal nerve. One option involves partial sectioning of the root with complications such as facial numbness and incomplete or no pain relief. We describe an alternative, namely open glycerol rhizotomy (OGR), carried out intraoperatively when no discreet vascular compression is observed. METHODS: A total of 101 consecutive MVD cases for TN were reviewed, 14 of which had no vascular compression identified by an experienced surgeon. Included in these 14 were patients who failed previous procedures (e.g., MVD, gamma knife). For the 14 negative explorations, a droplet of glycerol was placed 3 to 4 mm distal to the root entry zone of the sensory portion of the trigeminal root. These cases were retrospectively reviewed for follow-up and to evaluate outcomes. RESULTS: The procedure was tolerated well by all patients. Thirteen of the 14 experienced immediate complete facial pain relief; seven of the 14 experienced initial facial numbness described as mild, but all patients retained their ipsilateral corneal reflex. Reassessment at 6 weeks revealed that nine of 14 had no pain, two were improved, and three had the same pain as prior to surgery. Between 6 months and 2 years after surgery, two patients restarted medication and two had a percutaneous glycerol rhizotomy. There were no cases of anesthesia dolorosa. There were no other neurological deficits and no deaths. CONCLUSION: Intraoperative glycerol rhizotomy appears to be effective when no significant vascular compression is observed and is associated with outcomes comparable to other rhizotomy techniques. Additional follow-up is necessary to establish long-term results, but the initial results suggest the potential for an alternative method of rhizotomy.