Abstract and Introduction
Objective: In microvascular decompression surgery for trigeminal neuralgia and hemifacial spasm, the bridging veins are dissected to provide the surgical corridors, and the veins of the brainstem may be mobilized in cases of venous compression. Strategy and technique in dissecting these veins may affect the surgical outcome. The authors investigated solutions for minimizing venous complications and reviewed the outcome for venous decompression.
Methods: The authors retrospectively reviewed their surgical series of microvascular decompression for trigeminal neuralgia and hemifacial spasm in patients treated between 2005 and 2017. Surgical strategies included preservation of the superior petrosal vein and its tributaries, thorough dissection of the arachnoid sleeve that enveloped these veins, cutting of the inferior petrosal vein over the lower cranial nerves, and mobilization or cutting of the veins of the brainstem that compressed the nerve roots. The authors summarized the patient characteristics, operative findings, and postoperative outcomes according to the vascular compression types as follows: artery alone, artery and vein, and vein alone. They analyzed the data using chi-square and 1-way ANOVA tests.
Results: The cohort was composed of 121 patients with trigeminal neuralgia and 205 patients with hemifacial spasm. The superior petrosal vein and its tributaries were preserved with no serious complications in all patients with trigeminal neuralgia. Venous compression alone and arterial and venous compressions were observed in 4% and 22%, respectively, of the patients with trigeminal neuralgia, and in 1% and 2%, respectively, of those with hemifacial spasm (p < 0.0001). In patients with trigeminal neuralgia, 35% of those with artery and venous compressions and 80% of those with venous compression alone had atypical neuralgia (p = 0.015). The surgical cure and recurrence rates of trigeminal neuralgias with venous compression were 60% and 20%, respectively, and with arterial and venous compressions the rates were 92% and 12%, respectively (p < 0.0001, p = 0.04). In patients with hemifacial spasm who had arterial and venous compressions, their recurrence rate was 60%, and that was significantly higher compared to other compression types (p = 0.0008).
Conclusions: Dissection of the arachnoid sleeve that envelops the superior petrosal vein may help to reduce venous complications in surgery for trigeminal neuralgia. Venous compression may correlate with worse prognosis even with thorough decompression, in both trigeminal neuralgia and hemifacial spasm.
Two types of posterior fossa veins are involved in microvascular decompression surgery, namely, the bridging veins and veins of the brainstem. Bridging veins often traverse the surgical corridors to the trigeminal and facial nerves. Veins of the brainstem may sometimes compress the trigeminal and facial nerve roots and cause trigeminal neuralgias[4,8,10,11,15,17] and hemifacial spasms,[2,6,7] respectively. Therefore, venous dissection is essential in microvascular decompression surgery, but the dissection of these veins may cause severe surgical complications.[3,12,13,22] To elucidate safe and effective methods of venous dissection, we reviewed our surgical series of microvascular decompressions for trigeminal neuralgia and hemifacial spasm. We preserved the superior petrosal vein and its tributaries in the surgeries for trigeminal neuralgia, whereas we cut the inferior petrosal vein near the accessory nerve early in the surgeries for hemifacial spasm. We illustrate the usefulness of cutting arachnoid membrane that enveloped the superior petrosal vein to preserve this vein. This arachnoid dissection enables further dissection around the trigeminal nerve root to be performed safely. We also focus on the clinical importance of venous compression to the trigeminal[4,8,10,11,15,17] and facial nerve roots.[2,6,7] We summarize the cases with venous compression and their long-term outcomes after microvascular decompression surgery.
Neurosurg Focus. 2018;45(1):e2 © 2018 American Association of Neurological Surgeons