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Clinical Records
Introduction
Lyme disease, or Lyme borreliosis, is the most common tick-borne human infection in the northern hemisphere (carried by the tick Ixodes ricinus), occurring mainly in North America, Asia and Central Europe. There are 20 000 new cases every year (9.1 cases per 100 000 population) in the USA,1whilst in Europe 65 500-85 000 cases are reported every year.2,3Prevalence of borrelia infection in ticks in Europe is approximately 13.7 per cent.2,4The first Portuguese human case of Lyme borreliosis was identified in 1989.5Data have shown an incidence of 0.04 per 100 000 inhabitants, with the highest number of laboratory confirmed cases being from the Lisbon district.6
This report aims to describe a case of Lyme disease where the only manifestation was unilateral sudden sensorineural hearing loss (SNHL). It is a rare presentation of a rare disease in Portugal.
Case report
A 40-year-old woman presented with a 48-hour history of right SNHL, tinnitus and mild peripheral vertigo, with no other symptomatology. Pure tone audiometry revealed average hearing thresholds of 52.5 dB in the symptomatic ear, which was in accordance with Fetterman and colleagues' criteria for sudden SNHL.7The patient was commenced on systemic corticosteroid (prednisolone 1 mg/kg/day for 10 days, followed by a tapering dose for 5 days). In addition, she received 10 sessions of hyperbaric oxygenation (2.5 ATA, 100 per cent oxygen for 90 minutes each session). Post-treatment audiometry revealed hearing thresholds of 20 dB in the right ear, demonstrating a recovery of 32.5 dB.
Our department has created a protocol (based on discussion of peer-reviewed articles) that includes laboratory tests for Borrelia burgdorferi; this protocol was produced with the aim of developing guidelines for the diagnosis and treatment of sudden SNHL. However, in order to prevent a long delay between the onset of the hearing loss and treatment, patients start corticosteroid and hyperbaric oxygen treatment as soon as possible.
The three-dimensional (3D), T2-weighted magnetic resonance imaging (MRI) scans revealed focal loss of signal in the right semicircular canals, suggesting labyrinthitis (Figure 1).
Fig. 1
Three-dimensional, T2-weighted magnetic resonance images of the right inner ear, showing: (a) focal loss of signal in...