Labyrinthitis With Negative MRI As a Precursor to Rapidly Developing Primary CNS Lymphoma of the Cerebellopontine Angle.

Background: Few case reports have described primary central nervous system lymphoma (PCNSL) presenting as a cerebellopontine angle (CPA) lesion in HIV-positive patients. We describe a rare presentation of rapidly progressing PCNSL of the CPA/internal auditory canal (IAC) as labyrinthitis with initial negative MRI in an HIV-positive patient. Case: A 58-year-old male with well-controlled HIV presented with sudden left sensorineural hearing loss, tinnitus, and imbalance. Vestibular testing suggested an uncompensated left peripheral vestibular weakness. MRI demonstrated facial and cochleovestibular nerve enhancement within the CPA and IAC. The presumptive diagnosis of labyrinthitis was made. Two months later, he presented to his infectious disease provider with left facial weakness and disequilibrium and was treated for presumed Bell's palsy. One month later, he presented with left corneal reflex dysfunction, decreased visual acuity, diplopia, and worsening ataxia. Repeat MRI demonstrated a new 3.6 cm lesion of the left CPA/IAC with vasogenic edema. Despite location, the mass lacked the brainstem compression characteristic of other extra-axial CPA masses such as vestibular schwannoma. Flow cytometry and cytology from cerebrospinal fluid was consistent with primary central nervous system large B-cell lymphoma. Conclusions: We present a unique case of rapidly progressing PCNSL of the CPA/IAC in an HIV-positive patient, presenting initially as labyrinthitis with negative MRI followed by development of multiple cranial neuropathies and 3-month repeat MRI demonstrating a large CPA mass. In HIV-positive patients with a similar initial presentation, PCNSL should considered early in the diagnostic evaluation with close clinical monitoring and a low threshold for repeat imaging.