Findings: T1, T2 and FLAIR axial images were performed which demonstrate prominence of the CSF spaces bifrontally. There are leptomeningeal signal abnormalities diffusely. Gyral enhancement is present on post-Gadolinium images (not shown). Additionally, fluid is visualized with both middle ears.
Diagnosis: Bacterial meningitis.
Discussion: Bacterial meningitis is potentially life threatening disease which in the infant (>2 months), is usually caused by Haemophilus Influenza, Strep, Pneumonia and Neisseria Meningitidis. Complications from such infections include: communicating hydrocephalus secondary to CSF loculations of purulent exudate or obstructive hydrocephalus from ependymitis or ventriculitis. In addition, inflammatory processes can lead to arteritis and venous thromboses which produce cerebral ischemia and infarction. Subdural effusion, as seen in this case is usually due to H. Flu in children. These can become infected and produce subdural empyemas.
Intracranial involvement as a direct result of middle ear infection has been reported with an incidence from 0.54%. The mortality rate in these cases can be as high as 25%. Possible pathways for the migration of pathogens from the middle ear to the meninges include: 1) systemic via the bloodstream, 2) along preformed tissue planes such as the posterior fossa, 3) via temporal bone fractures, or 4) through the oval or round window membranes labyrinthine. Congenital malformation of the stapedial footplate has also been implicated. In a study of eight infants with otitis media who died of meningitis, chronic inflammatory cells were found in the round window and cochlear aqueduct. This suggested a possible route of entry for pathogens to the cerebrum. Importantly on physical exam, all tympanic membranes were intact. Therefore, such a condition may be undetected or undetectable, particularly in chronic cases.
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