Isolated Meckel's Cave and Cavernous Sinus Amyloidomas Mimicking Central Skull Base Tumors

Objective: Rarely, non-neoplastic pathologies can mimic tumors of the skull base. Increased morbidity could result if empiric treatment is undertaken based on a radiographic presumed diagnosis alone.

Methods: We present the case of a 39-year-old woman who presented with a 10-year history of slowly progressive left facial numbness with associated trigeminal neuralgia. Four years prior to her presentation, she developed right facial numbness and neuralgic pain, which became intractable and severe. In addition, she reported intermittent diplopia that eventually prompted imaging, which revealed abnormal enhancement and fullness involving bilateral Meckel's caves and cavernous sinuses. Imaging of the entire neural axis was otherwise normal. CSF analysis and systemic workup for cancer or inflammatory or infectious etiologies were unrevealing. Preoperatively, the differential diagnosis included inflammatory and neoplastic processes.

Results: The patient underwent a right frontotemporal craniotomy and subtemporal exploration of the right Meckel's cave. Firm, avascular tissue was discovered adherent to the trigeminal nerve and ganglion and surrounding dura. Histopathological studies showed entrapment of the ganglia by amyloid and amyloid deposition within the microvasculature with characteristic apple-green birefringence. Mass spectroscopy detected a peptide profile that was consistent with light chain amyloid, kappa subtype. Hematologic workup was subsequently pursued and showed no evidence for underlying myeloma, lymphoma, or systemic amyloidosis.

Conclusion: We present a very rare case of amyloidomas of bilateral Meckel's caves and cavernous sinuses causing progressive neurologic deficits. Although extremely rare, primary amyloidoma should be considered in the differential diagnosis of central skull base tumors.