Trigeminal Amyloidoma: A Report of Two Cases and Review of the Literature

Abstract

Cerebral amyloidomas, characterized by localized amyloid deposits in the nervous system in the absence of systemic disease, are rare. These typically consist of immunoglobulin light chain (AL)-type, predominantly lambda. Trigeminal nerve involvement is exceptionally rare with only 21 previously reported cases, three with bilateral disease. We report two additional cases of amyloid localized to Meckel's cave with secondary involvement of the trigeminal nerves bilaterally, with protein characterization by mass spectrometry. The patients, both females, 39 and 49-years-old, respectively, presented with the insidious onset of progressive trigeminal neuropathy, including pain and numbness with sensory loss, refractory to medical therapy. One patient experienced bilateral symptoms. Magnetic resonance imaging demonstrated abnormal thickening and contrast enhancement along Meckel's cave bilaterally in both cases. The clinical differential diagnosis included benign neoplasms and inflammatory disorders. At the time of biopsy, the trigeminal nerve was noted to be enlarged and multinodular in one case and associated with abnormal soft tan tissue in the other case. Microscopically, the nerve biopsies showed extensive Congo red-positive amyloid deposits. Liquid chromatography tandem mass spectrometry demonstrated that the amyloid was of (AL)-type in both cases (AL [kappa] in one case and AL [lambda] in the other). After extensive evaluation, there was no evidence of systemic involvement. Both patients received localized radiotherapy for their refractory symptoms. One patient has stable symptomatology and imaging. No follow-up is available for the other patient.

Keywords: amyloidoma; cerebral amyloidoma; gasserian ganglion; trigeminal nerve.

Fig. 1

Case 1: Axial T1-weighted ( A ) and coronal ( B ) MRI sequences with fat saturation demonstrating homogenous enhancement with expansion of Meckel's cave and cavernous sinus bilaterally (red arrows). Axial T2-weighted image ( C ) shows Meckel's cave contains abnormal signal (red arrows), which is isointense or slightly hypointense to brain parenchyma bilaterally. Case 2: Postcontrast axial T1- weighted ( D ) and coronal ( E ) MRI sequences with fat saturation demonstrating homogenous enhancement of an infiltrating process within left Meckel's cave and cavernous sinus (red arrows). Axial T1-weighted ( F ) MRI sequence eleven months after radiotherapy shows stable disease in left greater than right Meckel's cave (red arrow). MRI, magnetic resonance imaging.

Fig. 2

Amyloid deposits involving the ganglion ( A, B ). Positive staining and apple-green birefringence with Congo red ( C, D ).

Fig. 3

Amyloid deposition involving endoneurium ( A, B ). Positive staining and apple-green birefringence with Congo red ( C, D ).

Fig. 4

Proteomic identification of light chain amyloid in trigeminal nerve amyloid deposits. Congo red-positive deposits were microdissected and analyzed using liquid chromatography with mass spectrometry (LCMS/MS) as described in the Methods. A protein identification report showing the universal amyloid markers (highlighted with blue/gold double stars) and type deterministic markers (highlighted with blue stars). The numbers displayed in green boxes represent the total number of MS/MS spectra matched to the listed protein. Cases 1 and 2 are shown with duplicate independent microdissections and subsequent LCMS/MS analysis. LCMS, liquid chromatography mass spectrometry; MS, mass spectrometry.