RADT-42. DISSEMINATED TUMORAL AMYLOIDOSIS OF THE CRANIAL NERVES IN THE ABSENCE OF SYSTEMIC DISEASE: CASE REPORT

Abstract Tumoral amyloidosis, characterized by tumor-like deposits without systemic disease, is rare in the central nervous system. Most often located in the periventricular white matter, tumoral amyloidosis typically consist of immunoglobulin light chains (AL). While prior reports describe cases of tumoral amyloidosis isolated to the trigeminal nerve, we report herein a first known case of diffuse cranial nerve involvement. The patient is a 43-year-old man who presented with left trigeminal dysesthesias, which led to self-excoriation and erosion of the left naris. On exam, he had absent sensation in the V1-V3 distributions, left trochlear nerve palsy, and bilateral abducens nerve palsies. Imaging demonstrated significant thickening of the left trigeminal nerve and diffuse cisternal contrast enhancement of the other cranial nerves, including the oculomotor, abducens, facial, and glossopharyngeal nerves. Work-up began with a lumbar puncture that found elevated protein with otherwise benign results, including flow cytometry. He was therefore recommended to undergo open biopsy of the left trigeminal nerve and cavernous sinus. Pathology from this surgery demonstrated congo red- positive AL amyloid deposits. Following this pathologic diagnosis, he subsequently underwent a full workup for systemic amyloidosis including bone marrow biopsy, abdominal fat pad biopsy, and a PET CT scan. Biopsy of a long nodule was negative for amyloidosis. Systemic amyloid testing did not demonstrate non-CNS sites of amyloid deposition. Medical therapy with daratumumab, cyclophosphamide, bortezomib, and dexamethasone was started but then discontinued due to ineffectiveness. He underwent radiation treatment of 4500 cGy to the left cavernous sinus where the tumoral amyloidosis was most severe. He has had no further progression of his disease. Tumoral amyloidosis of the cranial nerves remains a rare and poorly-understood disease. Prior reports have described the disease isolated to the trigeminal nerve. This report raises attention to this diagnosis in cases of rare multi-nerve involvement and suggests that radiation may be a useful first-line treatment.