Materials and methods
In this retrospective, observational study, medical records from all
patients admitted to hospitals in Skåne county with the ICD-code G00
(bacterial meningitis) between 2000 and 2017 were retrieved. Exclusion
criteria were neonatal, viral, fungal or non-infectious meningitis,
borrelia, nosocomial, postoperative, or ventricular shunt-related
infections.
Information about gender, age, otoscopy results, CT/MRI signs of middle
ear infection, microbiological results, subjective hearing loss and
hearing tests were extracted from medical charts. Where pure tone
audiograms were available, pure tone averages (PTA4; defined as the
average of hearing thresholds at 500, 1000, 2000 and 4000 Hz) were
extracted, as was presence of conductive hearing loss (defined as an
air-bone gap of ≥10 dB on at least two adjacent frequencies). Hearing
loss was defined as PTA4 ≥ 25 on either ear, and further subdivided into
mild (25-40 dB HL), moderate (41-70 dB HL) and severe (>70
dB HL). High frequency hearing was evaluated by calculating the average
hearing thresholds at 6000 and 8000 Hz.
By including data over 18 years in one of the most populous counties in
Sweden, we hoped to be able to estimate the incidence of bacterial
meningitis in Sweden over a long period of time. The proportion of
otogenic meningitis cases, time trends, microbiology and outcomes other
than hearing loss will be reported separately.
The study was approved by the Ethics Review Authority. The STROBE
guideline was used for the preparation of the manuscript.