This case report and associated scans demonstrate the importance of considering initial computed tomographic (CT) findings, along with the recent medical history, in a highly functioning individual who presents to your clinic 15 mos after a severe traumatic brain injury with increasing complaints of headache.
A 24-yr-old man was involved in a high-speed motor vehicle collision with resultant severe traumatic brain injury. The initial cortical contusions and cerebral edema with associated elevated intracranial pressures did not respond to positioning, hyperventilation, mannitol, sedation, and ventriculostomy drainage. He therefore successfully underwent a right frontotemporal craniectomy for pressure relief. A possible petrous bone fracture was also suspected based on CT scan bone windows; however, no specific treatment was indicated (Fig. 1). He progressively improved and, with extensive rehabilitation services, was successfully reintegrated into his preinjury job.
He had an uneventful course over the next year, with regular physiatric follow-up. He was treated with oral antibiotics for two right middle ear infections, with associated clear drainage. Approximately 15 mos postinjury, he began complaining to his physiatrist of increasing headaches, greater on the right than the left. He had had no new trauma or other significant events, including psychological stressors that he could relate to the relatively acute presentation of these headaches. When the headaches increased, despite appropriate dosing of oral medications, a head CT scan was performed (Fig. 2). A large, multilobulated lesion was noted in the right temporal lobe. It was consistent with an abscess, and after initiating intravenous antibiotics, surgical incision and drainage were performed. His symptoms resolved. The patient was treated with an additional 8 wks of home antibiotics. Unfortunately, the abscess had re-accumulated on repeat head CT scan 6 wks later. Repeat imaging studies demonstrated a persistent right petrous bone fracture with associated mastoid bone defect communicating with the mastoid air space that was thought to be a likely source of recurrent seeding of the abscess. A mastoidectomy with dural patch of the mastoid bone defect and repeat incision and drainage of the abscess was performed. An 8-wk course of home antibiotics was repeated. The patient has since been symptom free and without evidence of recurrent abscess.
Cerebral abscesses after traumatic brain injury are rare, occurring in less than 1% of all cases. The presence of a persistent dural tear with or without bony defect markedly increases the risk. Of all cerebral abscesses, 10% are specifically related to cranial trauma with direct contamination of the brain. Direct extension of an existing infectious source, most commonly a chronic otitic infection or, less commonly, a chronic sinusitis, occurs in 45–50% of all abscesses. Nearly one-quarter of cerebral abscesses occur by hematogenous spread from a distant source. The causes of the remaining 15% of abscesses are idiopathic.
Abscesses occur more commonly in men and more frequently in the first four decades of life. Mortality occurs in 5–15% of all cases, more commonly in the very young and very old, and in immunocompromised individuals. Clinically, the triad of fever, headache, and focal neurologic deficit is highly suggestive of a cerebral abscess, however infrequently it occurs. The clinical course is highly variable from indolent to fulminant. Although CT scan imaging can be rapidly obtained, findings on CT scanning may lag behind the clinical findings. Therefore, magnetic resonance imaging remains the diagnostic test of choice.
Although cerebral abscesses occur rarely after traumatic brain injury, vigilance should be maintained in individuals with significant risk factors (e.g., recurrent sinus or otitic infections, skull fractures, cerebrospinal fluid leak). Unfortunately, as in this case, a review of initial injury data and subsequent medical status is often necessary to identify these risk factors. A persistent headache, particularly one that has developed late after injury or is accompanied by fever, or new focal neurologic deficit may be the initial presentation of a cerebral abscess. Urgent CT scan imaging is recommended, followed by magnetic resonance imaging, if it is nondiagnostic. These individuals at risk for abscess are also at an elevated risk for more acute presentations of cerebral infection, such as meningitis. These infections may present similarly and need urgent care. An awareness of risk factors, close medical monitoring, reliable follow-up, and the inclusion of the neurosurgeons in the traumatic brain injury rehabilitation team are necessary to detect and manage cerebral abscess.