PMC6826320_01
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 2nd 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 3rd 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).
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F1
Non-enhanced cranial computed tomography (CT) scan was considered normal by emergency physicians [Figure 1a], so they decided to do a lumbar puncture. The following day, a retrospective assessment of the admission CT scan disclosed a laminar extracerebral collection adjacent to the falx [Figure 1a]. A definitive diagnosis of interhemispheric SDE was established using magnetic resonance imaging (MRI) [Figure 1b]. The small subdural collection (4 cm3) along the right side of the falx was found to be hyperintense on diffusion-weighted imaging (DWI) and with low signal intensity on apparent diffusion coefficient (ADC) [Figure 1b3-b4]. Nevertheless, control MRI demonstrated a notable enlargement of the subdural collection [22 cm3, Figure 1c], and thus we were consulted about the possibility of surgical drainage. Nevertheless, the MRI performed during the 3rd week showed an additional enlargement of the parafalcine collection [30 cm3, Figure 1d]. In addition, hyperintensity in the underlying brain on T2/fluid attenuated inversion recovery sequences pointing to a possible cerebritis was also observed [Figure 1d4].
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.
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F2
The small subdural collection (4 cm3) along the right side of the falx was found to be hyperintense on diffusion-weighted imaging (DWI) and with low signal intensity on apparent diffusion coefficient (ADC) [Figure 1b3-b4]. A large right parasagittal frontoparietal craniotomy was performed [Figure 2].
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 7th week after surgery (d). Hyperintense areas of the adjacent brain on T2-weighted MRI (b3, arrows) also resolved in the last MRI study (d3).
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F3
The small subdural collection (4 cm3) along the right side of the falx was found to be hyperintense on diffusion-weighted imaging (DWI) and with low signal intensity on apparent diffusion coefficient (ADC) [Figure 1b3-b4]. Based on her good clinical and radiological evolution, she was then treated with oral antibiotics (levofloxacin and metronidazole), which lasted 3 weeks until the follow-up MRIs demonstrated complete resolution of the subdural collection [Figure 3].