Parafalcine subdural empyema: The unresolved controversy over the need for surgical treatment

Abstract

Background: Parafalcine subdural empyema (SDE) is a rare entity consisting of pus accumulating below the longitudinal sinus, between the falx cerebri and the arachnoid layer covering the medial surface of the cerebral hemisphere. Its treatment strategy is controversial, but most clinicians have the general belief that appropriate treatment consists of prompt surgery combined with long-term antibiotic therapy. Nevertheless, six reports published in the 1980s provided evidence that antibiotic therapy alone is a safe and suitable option. The treatment strategies and outcomes of the 31 well-described cases previously published, in addition to our own, are discussed.

Case description: We report a 21-year-old female with a right-side parafalcine SDE who presented with fever, headache, generalized tonic-clonic seizures, and contralateral hemiparesis 3 weeks after undergoing sinonasal surgery. Despite clinical symptoms almost entirely abating after starting treatment with broad-spectrum antibiotics, magnetic resonance imaging performed during the 2^nd and 3^rd weeks showed progressive enlargement of the interhemispheric collection (from 4 cm³ to 30 cm³). We reflect on the treatment strategy chosen for this patient, who experienced a total recovery.

Conclusion: A nonsurgical strategy for parafalcine SDE might be contemplated for patients with a good clinical condition and no major midline shift on neuroradiological studies, given their usual indolent course and the relative difficulty in reaching the interhemispheric fissure. Conversely, surgery should be contemplated when the collection significantly enlarges despite antibiotic therapy. When surgical drainage is added to antibiotics, broad- range 16S ribosomal DNA polymerase chain reaction of the empyema is recommended to identify the causative organism as pus cultures are usually sterile.

Keywords: 16S ribosomal DNA polymerase chain reaction; Antibiotic therapy; Interhemispheric empyema; Parafalcine subdural empyema; Surgery.

Figure 1:

Preoperative neuroradiological studies. (a) Computed tomography scan performed the day of admission shows a hypodense laminar collection along the right side of the falx (arrow). (b) Magnetic resonance imaging (MRI) performed the following day. Axial (b1) and coronal (b2) T1 images confirm a frontoparietal interhemispheric collection without any mass effect. Collection shows high signal intensity on diffusion-weighted imaging (b = 1000 s/mm², b3) and reduced water diffusion in apparent diffusion coefficient map (b4). (c) Study performed during the 2^nd week of antibiotic therapy. T1-weighted, contrast-enhanced MRI (c1-c3) shows enlargement of the interhemispheric collection. c4: T2-weighted MRI demonstrates a hyperintense collection. (d) MRI performed during the 3^rd week. d1-d3: Additional enlargement of the collection is demonstrated. d4: Fluid attenuated inversion recovery MRI demonstrates hyperintense areas in the brain adjacent to the collection (arrows).

Figure 2:

Operative photographs. (a) The patient is placed in the supine position. A bicoronal skin incision was performed. (b) A large right parasagittal frontoparietal craniotomy was performed. (c) Following dura opening, a swollen brain was found. White liquid pus (arrow) was drained between two bridging veins (green arrowheads). (d) The subdural compartment was washed out, anteriorly and posteriorly, between the two bridging veins (green arrowheads) with saline and antibiotics using a soft rubber catheter.

Figure 3:

Postoperative neuroradiological studies. (a) Computed tomography scan performed the day after surgery shows a notable reduction of the interhemispheric collection. (b-d) Follow-up magnetic resonance imaging (MRIs) demonstrate progressive reduction of the collection (asterisk) along the right falx, which completely disappeared in the 7^th week after surgery (d). Hyperintense areas of the adjacent brain on T2-weighted MRI (b3, arrows) also resolved in the last MRI study (d3).