Background: The culprit of trigeminal neuralgia (TGN) may occur at any point between the nerve's root entry zone (REZ) and Meckel's cave. Meckel's cave meningoencephaloceles are rare middle cranial fossa defects that usually remain asymptomatic but may contain prolapsed trigeminal nerve rootlets and result in TGN. Their management and surgical outcomes remain poorly understood.
Objectives: To perform a systematic review of clinical presentation and surgical outcomes of middle fossa defects presenting with trigeminal nerve-related symptoms.
Materials and methods: A systematic review was conducted in accordance with the PRISMA guidelines for all reports of middle cranial fossa defects causing trigeminal nerve-related symptoms. The pathophysiology, presentation, surgical management, and outcomes are discussed and illustrated with a case.
Results: Initial search from inception to March 2021 identified 33 articles for screening. After applying inclusion and exclusion criteria, 6 articles were included representing a total of 8 cases in addition to our case (n = 9). All 9 patients were females and 33.3% (n = 3) presented with classic trigeminal neuralgia. "Empty sella" syndrome and radiologic signs of intracranial hypertension were present in 40%-62%. No patient presented with cerebrospinal fluid leak. The preferred treatment modality was surgical with subtemporal extradural repairs using combinations of autologous fat and muscle grafts and synthetic dura. Postoperative outcomes were only available in 55.5% (n = 5) of the cases, and nearly all reported complete symptom resolution, except for one case in which the meningoencephalocele wall was incised, along with trigeminal rootlets adhered to it. Our patient had immediate and durable symptom relief after a 4-year follow-up.
Conclusions: MEC containing prolapsed trigeminal nerve rootlets can cause typical trigeminal neuralgia from chronic pulsatile stress. This supports the hypothesis that the compressive or demyelinating culprit can locate more ventrally on the course of the trigeminal nerve. Subtemporal extradural surgical repairs can be safe, effective, and durable. Incising the MEC wall should be avoided as it may have trigeminal rootlets adhered to it.
Keywords: Encephalocele; Meckel's cave; meningocele; meningoencephalocele; petrous apex; root entry zone; skull base; transition zone; trigeminal neuralgia.