Our patient was a 70-year-old Caucasian male with a past medical history notable for hypertension, noninsulin-dependent diabetes, hypercholesterolemia and multiple myeloma previously treated with stem cell therapy. He presented with a two-day history of acute diplopia that was constant, binocular and exacerbated with right gaze. The patient also reported a new persistent right occipital headache. The patient denied ocular pain, ataxia or vertigo. Upon further questioning, the patient reported fatigue and a new persistent right occipital headache.

EXAMINATION

A focused examination found the following:

• Head: NCAT (normocephalic atraumatic), PERRLA (pupils equal, round, react to light, accommodation)
• Distance visual acuity with correction: 20/40 OU
• Pupils: briskly reactive, no relative afferent pupillary defect OU
• Motility: -2 abduction OD
• Dilated fundus exam: normal nerve, macula, vessels and periphery OU

Our differential diagnosis included intracranial hypertension, myasthenia gravis, thyroid eye disease, giant cell arteritis, microvascular nerve palsy or a compressive lesion of the orbit or cavernous sinus.

LABS/IMAGING

The complete blood count was significant for mild anemia and a platelet count of 34 pl/mL. The erythrocyte sedimentation rate and C-reactive protein were less than 15 mm/hr and 5 mg/L, respectively. An MRI of the brain/orbits was notable for a 1.4 x 1.3 x 1.2 cm mass in the right side of the clivus, with a soft tissue component invading the right cavernous sinus. The homogenous soft tissue mass was found to be replacing the normal fatty marrow with mild enhancement, consistent for multiple myeloma. The combination of clinical symptoms — including right-sided occipital headache and persistent diplopia, history of multiple myeloma and imaging indicating an invasive lesion — pointed to a diagnosis of a compressive lesion of CN VI in the cavernous sinus secondary to a multiple myeloma relapse. The patient was referred to hematology, oncology and radiation oncology, where the patient was started on a 3000-cGy treatment plan in 300-cGy fractions.

DISCUSSION

Multiple myeloma is a neoplastic proliferation of heterogeneous plasma cells that accounts for approximately 10% of hematologic malignancies and has a reported 10% to 20% mortality in the first two months of presentation.¹ Classic complications from multiple myeloma include renal failure, anemia, hypercalcemia and bone pain from the destructive lesions.²

Involvement of the central nervous system and subsequent neurological sequelae are rare and often the result of an epidural plasmacytoma compressing peripheral nerves.³ While extension into the cavernous sinus has been documented, isolated cranial nerve lesions are rare.⁴ Our patient presented with bilateral horizontal diplopia and headache secondary to invasion of the malignancy into the right cavernous sinus.

Diagnosis is determined on the constellation of physical exam findings; laboratory work, including a CBC, serum calcium and creatinine levels, serum and urine protein electrophoresis, serum FLC (free light chain) assay; and CT or MRI imaging identifying the mass.⁵ Accurate diagnosis is extremely important, as the treatment for multiple myeloma is unique from other skull-base tumors: Due to its high radiosensitivity, radiation and stem cell therapy are the primary treatment modality.⁵ OM

Special thanks to the Memphis Veterans Administration Medical Center for its assistance.

REFERENCES

1. Kariyawasan CC, Hughes DA, Jayatillake MM, Mehta AB. Multiple myeloma: causes and consequences of delay in diagnosis. QJ Med. 2007;100:635-640. Epub 2007 Sep 10.
2. Kyle RA, Gertz MA, Witzig TE, et al. Review of 1027 patients with newly diagnosed multiple myeloma. Mayo Clin Proc. 2003;78:21-33.
3. van Ginkel S, Snijders TJ, van de Donk NW, Klijn CJ, Broekman ML. Progressive neurological deficits in multiple myeloma: meningeal myelomatosis without MRI abnormalities. J Neurol. 2012;259:1231-1233.
4. Siyag A, Soni TP, Gupta AK, et al. Plasmacytoma of the skull-base: a rare tumor. Muacevic A, Adler JR, eds. Cureus. 2018;10:e2073.
5. Rajkumar SV, Kumar S. Multiple myeloma: diagnosis and treatment. Mayo Clinic Proc. 2016;91:101-119.

About the Authors

William Evans, BSE, is a fourth-year medical student at the University of Tennessee who is interested in pursuing a residency in ophthalmology. Prior to attending medical school, William earned a biomedical engineering degree with honors from Arizona State University.

Devin West, MD, is a comprehensive ophthalmologist with North Texas Ophthalmology Associates in Wichita Falls, Texas. He graduated from Saint Louis University School of Medicine (St. Louis, Mo.) with distinction in research for his work on herpetic eye disease and currently focuses on cataracts and glaucoma.

Lauren Ditta, MD, is a professor of ophthalmology at the University of Tennessee Health Science Center in Memphis. She is the director of pediatric neuro-ophthalmology at Le Bonheur Children’s Hospital, in Memphis.

Disclosures: The authors have no relevant financial interests.