Three Cases of Trigeminal Neuralgia with Radiographic Absence of Meckel's Cave.

Trigeminal neuralgia (TN) is a debilitating but treatable disease. Classic TN has referable vascular compression of the trigeminal nerve, but rarely secondary sources of anatomic compression will present, including vascular malformations, aneurysms, or tumors. Understanding the etiology of the patients' symptoms leads to targeted treatment. Three patients presented with symptoms consistent with TN: shooting, paroxysmal pains in the distribution of the trigeminal nerve. However, imaging revealed no vascular conflict at the root entry zone of the trigeminal nerve. Instead, on the affected side Meckel's cave was absent. No other compressive mass lesion was identified. In all three cases, patients were offered both Gamma Knife Radiosurgery and surgical decompression of Meckel's cave. All 3 patients elected to proceed with stereotactic radiation and reported improvement in pain. Many cases of classic TN can be explained by neurovascular conflict at the trigeminal root entry zone, but secondary sources of compression or restriction along the nerve can result in similar symptomology. In this case series, an absent or hypoplastic ipsilateral Meckel's cave may have produced symptoms consistent with TN. Imaging with fine cuts through Meckel's cave is an important diagnostic tool.