A 48-year-old man with no relevant medical history initially presented to his primary care physician for evaluation of hearing loss. He described a two-year history of tinnitus in both ears that progressed to bilateral hearing loss. On exam, he was noted to have clear external ear canals with normal-appearing tympanic membranes. Audiometry testing showed bilateral sensorineural hearing loss (SNHL) from 250 to 8,000 Hz. The patient was given hearing aids, but within two months he progressed to complete bilateral hearing loss. He then presented to a neurology clinic and was admitted to the hospital for further workup.
On admission, the patient reported worsening headaches associated with balance issues especially while ambulating, gait disturbance with unsteadiness on his feet, and dizziness. He took no medications and reported occasional alcohol use, but no tobacco or drug use. He had emigrated from Central America over 10 years ago. Physical exam, including neurological exam, was normal aside from the hearing loss. Initial blood work was unremarkable.
A lumbar puncture showed a protein level of 1,020 mg/dL (reference range, 12 to 60 mg/dL) with a glucose level of 31 mg/dL (reference range, 40 to 70 mg/dL).
Cryptococcal cerebrospinal fluid Ag returned positive, with titers of 1:2,560 (normal is undetectable). An MRI showed bilateral lesions in the internal auditory canals with diffuse nodular enhancement within the bilateral Sylvian fissures (Figure 1, Figure 2).
A broad work-up for underlying causes of immunosuppression, including HIV, tuberculosis, coccidioidomycosis, sarcoidosis, and cirrhosis, was negative. Two months after discharge, the patient continued to see medical specialists, without resolution of hearing loss.
This diagnosis is cryptococcal meningitis. Only 17% of cryptococcal meningitis cases occur in immunocompetent individuals. Cryptococcus neoformans serotypes B and C account for the greatest number of infections in immunocompetent hosts; however, recent studies suggest that Cryptococcus gattii may affect immunocompetent individuals at a higher rate.
SHNL from cryptococcal meningitis is often progressive and bilateral. The proposed mechanism is invasion of the temporal bone with destruction of spiral ganglion cells and cochlear nerve fibers and meningitic infiltration of cryptococcus with arachnoiditis. Predictors of SNHL include a high cryptococcal antigen titer of more than 1:1,024, concomitant visual impairment, and meningeal enhancement on MRI, specifically Sylvian fissure enhancement, seen in approximately 30% of patients.
No factors have been definitively identified to estimate the chance of hearing improvement in SNHL. Since progression of hearing loss is variable, routine hearing assessments after treatment are critical, as the presence of otoacoustic emissions may indicate the percentage of recovery to anticipate. Additional interventions, beyond the guideline-based treatment of amphotericin B plus flucytosine followed by fluconazole, have not been studied. As the nerve damage in cryptococcal meningitis is often retrocochlear, the efficacy of cochlear implants to treat hearing loss is uncertain, but likely minimal. It remains unclear what percentage of patients recover and to what degree.
- SNHL is an uncommon symptom in cryptococcal meningitis, but the diagnosis should be considered even in immunocompetent patients.
- Predictors of SNHL in cryptococcal meningitis include elevated titers and Sylvian fissure enhancement on MRI.