The majority are supratentorial in location, common in developing countries, especially in the pediatric age group.
A 12-year old child and a 2-month old infant developed, in the wane of a purulent meningitis, the former, an infratentorial subdural empyema, the latter, a large, encapsulated, haemoorhagic, aseptic subdural effusion, in the right parieto-temporo-occipital region. In both cases, signs of intracranial hypertension dominated the clinical picture. Neuroradiological investigations permitted diagnosis and localisation of the expansive processes, whose subdural position was recognized at operation and confirmed by histopathological examination. According to the literature, purulent meningitis is a rare cause of subdural empyema, except in infants; the solely infratentorial location is also unusual. Sterile subdural effusion is a more common complication of purulent meningitis in infancy, but the unilateral posterior supratentorial location is also a peculiar feature. Subdural collections after memingitis may be aseptic and possibly haemorrhagic, or septic and purulent; these different modes of presentation correspond perhaps to different degrees or stages of subdural pathological changes in the neighbourhood of leptomeningeal infection 2).
Forty one cases of subdural empyema treated between 1977 and 1988 at the Postgraduate Institute of Medical Education and Research. Chandigarh, have been analysed. The patients ranged from 9 days to 80 years of age. There were 22 children, including 11 infants. Fever, altered sensorium and seizures were the most common symptoms present for 1 day to 6 months. Otogenic infection was the commonest aetiological factor followed by postoperative and posttraumatic causes. Thirty seven patients had supratentorial empyemas, including 4 with parafalcine collections, three had infratentorial empyemas, and in one there was extension of the empyema from the supratentorial to the infratentorial compartment. Therapeutic modalities used included percutaneous needle aspirations in infants and burr hole evacuation and craniotomies in adults. A wide spectrum of organisms was detected. Mortality in this series was 24%, which was mainly attributable to the deteriorated neurological status prior to treatment. A detailed review of the literature has been given, highlighting various controversies in the management of SDE. Important prognostic factors and a treatment plan are suggested 3).
Seventeen patients with this infection, treated between 1967 and 1974, are analyzed and compared to published series with particular regard to diagnosis using newer procedures and treatment, considering the primary focus of infection. The infection is usually located in the supratentorial spaces, is often bilateral, and results most often from para-nasal sinusitis (single most common cause), otitis, neurosurgical operative infections, and meningitis in infants. Patients suffering from subdural empyema generally present with rapid onset of depressed sensorium, seizures, focal neurological deficits, and signs of increased intracranial pressure, following a period of days to weeks characterized by headache and fever. All 17 of our patients demonstrated localizing neurological signs and 16 manifested either fever or leukocytosis. Diagnostic studies, except for cerebral arteriography, do not reliably corroborate or exclude the diagnosis. Cerebral arteriography established the diagnosis and defined the location and extent of the empyema in all of our cases. The EEG and brain scan produced frequent false-negative and/or non-localizing results in 10 and 8 patients, respectively. The cerebrospinal fluid was abnormal from all 15 patients examined by lumbar puncture, but the findings were similar to those in other infectious and non-infectious central nervous system diseases. Signs of transtentorial herniation developed within eight hours following lumbar puncture in three of seven patients who had exhibited signs of increased intracranial pressure before the procedure was performed. Bacterial cultures were positive in 13 of our cases. A review of our data and that of other studies indicates that the organisms associated with subdural empyema are consistent with those expected from infections of the primary site; e.g. sinusitis, otitis, meningitis, site of prior neurosurgery. A therapeutic approach is suggested which emphasizes specific antibiotic regimens appropriate to the primary site of infection and prompt neurosurgical intervention with evacuation of the subdural spaces bilaterally. In general, combination antimicrobial therapy employing high parenteral doses of penicillin G, a semi-synthetic penicillinase-resistant penicillin and chloramphenicol is recommended 4).