Glycerol Rhizotomy for the Management of Tumor-Associated Trigeminal Neuralgia

Background: Gross total resection of the adjacent tumor is often the most effective option for pain control in tumor-associated trigeminal neuralgia (TN). However, these tumors are often located near critical neurovascular structures or in difficult to access locations, and therefore gross total surgical resection may not always be feasible. One alternative to surgical resection in patients at high surgical risk or with unfavorable medical comorbidities is glycerol rhizotomy. However, there is currently limited evidence for the efficacy of glycerol rhizotomy in the management of tumor-associated TN, and a better understanding of this treatment option may optimize preoperative patient counseling and postoperative management.

Methods: To characterize the efficacy of glycerol rhizotomy in tumor-associated TN, we conducted a retrospective review of patients who underwent glycerol rhizotomy for TN at a tertiary care center between 2008 and 2019. Tumor association was identified by confirmation of adjacent mass to the trigeminal complex on MRI ([Fig. 1]). We evaluated baseline clinical and radiographic characteristics of patients who underwent glycerol rhizotomy for tumor-associated TN. We further assessed clinical outcomes including pain improvement, pain recurrence, and complications after glycerol rhizotomy. Neuralgic pain was measured based on the Barrow Neurological Institute (BNI) pain score.

Results: We identified 837 patients who underwent glycerol rhizotomy for TN, of which 23 (2.7%) patients had tumor-associated TN (Table 1). Five (21.7%) patients had previous surgical resection and 10 (43.5%) patients had prior radiation to the associated tumor. A total of 22 (95.7%) patients presented with typical trigeminal pain with 20 (87%) patients having an initial BNI pain score of IV or higher. Three patients were lost to follow-up at the time of study analysis. The mean follow-up time for the remainder patients was 21.7 months. Of the 20 remaining patients, neuralgic pain improvement was achieved in 17 (85%) patients (Table 2). The mean preoperative BNI score was 4.1 (SD 0.89) and mean postoperative BNI score at best response was 2.55 (SD 1.20, [Fig. 2]). Seven patients (35%) achieved complete resolution of pain, defined as having no facial pain and not taking any pain medications. In the three patients who had persistent pain postoperatively, two had reduction in either the dose or regimen of pain medications. During the follow-up period, pain recurred in eight (40%) patients. Seven (35%) patients experienced new postoperative facial numbness and no patients experienced hemorrhage, infection, CSF leak, hearing deficit, or mortality related to the procedure.

Conclusion: Tumor-associated TN can pose a challenging management problem as these tumors’ locations often prohibit safe gross total resection for alleviation of trigeminal pain. In the largest series to our knowledge, we demonstrate that glycerol rhizotomy for tumor-associated TN led to improvement in pain level or decrease in pain medication requirement in the majority of patients without significant complications. Therefore, glycerol rhizotomy can be an effective and safe minimally invasive tool in the management of tumor-associated TN patients who may not be amendable to gross total surgical resection.

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