Parafalcine Subdural Empyema

The Case

(A) Intial unenhanced CT scan demonstrating left frontal low-density area and free parasagittal air (B) Subsequent T1 enhanced MRI demonstrating a small parafalcine rim and increased collection. (C,D) Subsequent enhanced CT images demonstrating enlarged parafalcine and suprartentorial collections

An 84-year-old recently healthy and independently functioning man developed right-sided weakness and speech difficulty over a few hours, followed by a brief, generalized seizure. In the emergency department he was alert and had a low-grade fever, expressive dysphasia, leukocytosis, and right hemiparesis that affected his leg more than his arm.

A CT scan of his brain and sinuses revealed chronic pansinusitis with opacification of his frontal sinuses. It also showed intracranial air collections along his sagittal sinus on the left side, with left frontal cortical low-density areas. A CT venogram confirmed thrombosis of the anterior portion of his sagittal sinus, and MRI studies were consistent with left frontal cortical venous infarction along with a small parafalcine subdural collection. He was started on broad-spectrum intravenous antibiotics as well as anticonvulsants, and his sinuses were surgically drained under general anesthesia.

Enterobacter aerogenes was cultured from specimens taken from his sinuses, and the intravenous antibiotics were adjusted according to the sensitivity. He was anticoagulated with heparin sulphate at one day postoperatively. Over the next week his dysphasia and right arm strength gradually improved with normalization of the leukocytosis. The left-sided parafalcine collection enlarged, however, and was localized maximally to parietal and occipital areas, extending also to the left supratentorial surface.

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Discussion
The optimal surgical approach to subdural empyema is a topic that remains controversial despite the publication of results from related studies of large series of patients (2, 4, 5, 6). Subdural empyema is infrequently encountered in developed countries, possibly due to earlier and more aggressive management of sinusitis and middle ear infections. The regional inflammatory reaction to subdural purulent collections tends to persist beyond the intense systemic inflammatory response, which is frequently accompanied by superficial cerebritis that may lead to profound but often reversible neurological deficits. Venous thrombosis with its sequelae is also a common complicating factor (1). Affected patients require extended courses of antibiotics and frequently show reaccumulation of these inflammatory collections, necessitating more than one surgical intervention (4).

Craniotomy provides the opportunity for extensive exposure and irrigation of the subdural space and is especially helpful for locular empyemas. The CT-scan-guided, multiple burr hole procedures favored by some (2, 3) can effectively decompress and drain the collections early in the disease with minimal effect on the frail hyperemic brain and meninges, although repeat procedures likely would be required once the generalized inflammatory responses have subsided. Some proponents of craniotomy for subdural empyema advise against craniotomy for parafalcine collections (5). Little has been published on the optimal surgical strategy for this less common scenario. An interhemispheric approach in the presence of a swollen hyperemic brain with inflammatory adhesions and phlebitic vessels is no small undertaking in an acutely ill patient. With ster-eotactic techniques, these collections alternatively and effectively can be managed like deep-seated abscesses with transcortical drainage (7). When antibiotic treatment fails, the merits of each case should be weighed and a logical approach selected to evacuate these pernicious collections promptly and sufficiently.

Jacob Alant, MD, is a clinical fellow, and Rajiv Midha, MD, is professor and deputy head of the Department of Clinical Neurosciences at the University of Calgary in Canada. Dr. Midha is a member of the AANS Neurosurgeon Editorial Board. The authors reported no conflicts for disclosure.

References
1. Ackerman LL, Traynelis VC: Dural space infections, cranial subdural empyema and cranial epidural abscess, in Osenbach RK, Zeidman SM, eds: Infections in Neurological Surgery: Diagnosis and Management. Philadelphia: Lippincott-Raven, 1999, pp 85—100

2. Bok AP, Peter JC: Subdural empyema: burr holes or craniotomy? A retrospective computerized tomography-era analysis of treatment in 90 cases. J Neurosurg 78:574-578, 1993

3. Emery E, Redondo A, Berthelot JL, Bouali I, Ouahes O, Rey A: Intracranial abscess and empyema: neurosurgical management. Ann Fr Anesth Reanim 18:567-573, 1999

4. Hall WA, Truwit CL: The surgical management of infections involving the cerebrum. Neurosurgery 62: 2 Suppl SHC519-SHC530, 2008

5. Nathoo N, Nadvi SS, Gouws E, van Dellen JR: Craniotomy improves outcomes for cranial subdural empyemas: computed tomography-era experience with 699 patients. Neurosurgery 49:872-877, 2001

6. Nathoo N, Nadvi SS, van Dellen JR, Gouws E: Intracranial subdural empyemas in the era of computed tomography: A review of 699 cases. Neurosurgery, 44:529-535, 1999

7. Stephanov S, Sidani AH, Amacker JJ: Interhemispheric subdural empyema—case report. Swiss Surg 7:229-232, 2001

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Responses: Subdural Hematoma in a Patient With a VP Shunt This case was published in the AANS Neurosurgeon 17(4):46-47, 2009. Click here to review the case. The Case Subdural Hematoma in a Patient With a VP Shunt: What’s Your Diagnosis, Treatment Plan? Survey Results Summary Baseline CT before emergency presentation (left) and CT at emergency presentation (right). This case generated a lot of interest with more than 100 neurosurgeons and residents participating in the survey. An equal number of respondents (40 percent each) stated that the diagnosis was acute-on-chronic subdural hematoma and membranous/trabecular chronic subdural hematoma, while 15 percent said that a subacute subdural hematoma was the likely diagnosis. Most (80 percent) would have offered immediate surgical intervention directed at the hematoma. A delayed hematoma evacuation (12 percent) and initial intervention on the ventriculoperitoneal shunt alone (8 percent) were less popular choices. Respondents preferred craniotomy over either one or two burr holes, but notwithstanding the type of cranial opening, the majority (more than 65 percent) would have left a drain in place. Over three quarters of the respondents would have adjusted the valve to a higher setting, while a minority (15 percent) would have tied off the shunt or left it alone (5 percent). Based on the survey responses and the narrative comments, the overall consensus that emerged was to do both a subdural hematoma drainage procedure (with a subdural drain left in place) and to increase the valve setting. This recommendation is reflected in the narrative comments reproduced below. —Rajiv Midha, MD, Calgary, Canada Based on the survey results, it was unclear whether the respondents recommending medical therapy without surgery would have recommended or would have been obligated to do a biopsy to first prove the diagnosis. At least two of the respondents commented that they would prefer their local oncology and/or radiation oncology teams to provide radiation and/or chemotherapy to such patients without a proven histopathological diagnosis. Of the respondents recommending surgery, the vast majority would have performed a stereotactic biopsy, with the preponderance of this group preferring a frame-based system under local anesthesia rather than a frameless procedure under general anesthesia. One of the respondents actually recommended surgery for attempted gross total resection. The following comments demonstrate the range of opinions expressed by survey respondents. —Rajiv Midha, MD, Calgary, Canada Case Commentary Sometimes even the highest pressure setting, on current adjustable shunts, is insufficient to allow the subdural hematoma to resolve. There are higher pressure adjustable shunts in development that will help. As with most conditions there are several methods of management that will correct the condition, but we don’t know the single most effective method yet. I hope the studies will be done so true evidence-based medicine can be practiced, instead of edict from the powers that be based on their unproven conclusions. —Hunt Bobo, MD, Tupelo, Miss. I would not leave the drain for more than 24 hours. I would repeat the CT scan and then increase the shunt pressure in a step-wise manner and monitor the result with CT. —Kambiz Kamian, MD, Ancaster, Canada