Otosyphilis: a cause of hearing loss in adults with HIV

The recent increase in early syphilis infections in Australia has been accompanied by the re-emergence of disease manifestations unfamiliar to modern clinicians. Otosyphilis is a rare cause of sensorineural hearing loss and dizziness, and is important for clinicians to consider because the hearing loss is potentially reversible with early diagnosis and treatment. We report two cases of otosyphilis occurring in patients infected with HIV. In both cases, the diagnosis of otosyphilis was initially missed, despite review by several specialist medical units.

Cochleovestibular dysfunction is a well described complication of congenital and acquired syphilis. In acquired syphilis, it can occur at any stage of infection. In the pre-penicillin era, hearing loss was reported in 17% of patients with early latent infection and in 80% with symptomatic neurosyphilis.1

Cochleovestibular symptoms of neurosyphilis can occur via two main mechanisms. First, the eighth cranial nerve may be affected, for example in acute syphilitic meningitis. In these situations, hearing loss is usually accompanied by other neurological deficits, and findings on cerebrospinal fluid (CSF) examination will usually be abnormal. Second, and more commonly, hearing loss and vestibular symptoms present without features of coexisting neurosyphilis. These symptoms may occur at any stage of syphilis and are thought to result from direct damage to the vestibulocochlear apparatus. During dissemination, spirochaetes invade the inner ear perilymph, leading to inflammation of the labyrinthine structures and otic capsule. CSF parameters are usually found to be normal but, histologically, fibrosis and ischaemic necrosis of labyrinthine structures are seen2 and endolymphatic hydrops is common. These pathological findings are identical to those of Meniere’s disease, explaining the similar clinical features.

Symptoms may be sudden or insidious in onset, and include bilateral (but often asymmetrical) sensorineural hearing loss, tinnitus and vestibular symptoms ranging from dizziness to severe vertigo. These symptoms closely resemble those of Meniere’s disease. Audiological testing shows sensorineural hearing loss, classically affecting low or high frequencies while sparing middle frequencies, and speech discrimination is poor.

Without treatment, otosyphilis will progress to profound deafness over months to years. Symptoms can fluctuate markedly over time, but the overall course is one of deterioration.3

There is no established case definition for otosyphilis, but the diagnosis should be made on the basis of a typical clinical presentation and positive serological test results for syphilis. This approach is purposely “over inclusive”, as otosyphilis is a potentially reversible cause of hearing loss.

The optimal treatment for otosyphilis is not established. The published literature is limited, consisting of case reports and small case series, but indicates that intravenous therapy is required. Intramuscular penicillin penetrates the perilymph poorly, and there are numerous reports of treatment failure when patients with otosyphilis are treated with penicillin regimens for latent syphilis. In one report, spirochaetes were recovered directly from a patient’s perilymph after treatment.4

Intravenous penicillin G at a dose of 18–24 million units per day, administered as 3–4 million units every 4 hours for 14 days, is the regimen recommended by the United States Centers for Disease Control and Prevention for treatment of otosyphilis. Probenecid is sometimes added, as are subsequent courses of intramuscular or intravenous penicillin.5 There is no high-level evidence to support any of these approaches.

Steroids are commonly coadministered, although there are few supporting clinical data. The rationale is that inflammation of the endolymphatic duct appears crucial to the pathogenesis of otosyphilis. A typical steroid treatment regimen is prednisolone at a dose of 0.5–1.0 mg/kg tapered over 1–2 months.

Regardless of the penicillin regimen used or whether steroids are employed, treatment outcomes are uniformly poor. Studies consistently show that auditory symptoms abate for only 30% of patients, while 7%–15% have improved results in audiological or speech discrimination tests. Tinnitus and dizziness have better outcomes, with 70%–80% of patients reporting improvement. Factors associated with better outcomes include duration of symptoms less than 5 years, age less than 60 years and fluctuating hearing loss.6

Both of these patients had HIV infection. Rates of syphilis are known to be substantially higher in the HIV-positive population.7 Otosyphilis has previously been described in patients infected with HIV, but relevant published literature is sparse. Patients co-infected with HIV and syphilis appear no different to HIV-negative patients in their clinical features, severity of disease or likelihood of developing this manifestation of syphilis.

In both of the cases we report, the diagnosis of otosyphilis was missed despite review by several specialist medical units. In the past few years, rates of early syphilis have risen markedly in Australia, predominantly among homosexual men.8 Relevant practitioners should be aware of this diagnosis in patients presenting with the symptoms described here, especially those at risk of syphilis, such as sexually active homosexual men, including those with HIV infection. Current guidelines recommend syphilis screening in sexually active homosexual men at least annually (up to every 3 months in those at higher risk) and at regular intervals in individuals infected with HIV.9