Diagnostic usefulness of intraoperative ultrasonography for unexpected severe brain swelling in ultra-early surgery for ruptured intracranial aneurysms.

Background: In ultra-early aneurysm surgery, the few hours from admission to aneurysm clipping present the greatest risk for an in-hospital recurrent hemorrhage, the development of acute hydrocephalus, and severe brain edema. Thus, severe brain swelling encountered after dural opening in a craniotomy can sometimes not be explained by a preoperative computed tomography (CT) scan. Therefore, neurosurgeons need a diagnostic tool to determine the exact cause of the brain swelling to apply appropriate intraoperative management. Accordingly, the authors propose a designated optimal ultrasound window for evaluating brain swelling during a pterional craniotomy, and assess its diagnostic usefulness and clinical impact.

Methods: Intraoperative ultrasonography was performed during pterional craniotomies to identify the causes of severe brain swelling in 23 out of 185 patients treated using a policy of ultra-early treatment after a subarachnoid hemorrhage. Paine's point was used as the sonographic window to provide axial images showing the anterior interhemispheric fissure, lentiform nucleus, insular cortex, sylvian fissure, and ventricular system.

Results: The intraoperative ultrasonography revealed significant changes from the preoperative CT findings in 9 (39.1 %) of the 23 patients. These changes included the occurrence of an intracerebral hemorrhage (ICH, n = 2) related to aneurysm rebleeding with aggravated hydrocephalus and the development (n = 5) or aggravation (n = 2) of acute hydrocephalus without rebleeding. Meanwhile, for 14 (60.9 %) of the 23 patients, the ultrasonography showed no intracranial changes. For the total 23 patients with severe brain swelling, the intraoperative management included aspiration of an ICH (n = 3), a ventriculostomy (n = 16), and medical management (n = 8) with additional mannitol and/or mild hyperventilation.

Conclusions: When severe brain swelling is encountered during a pterional craniotomy for clipping a ruptured aneurysm, an intraoperative ultrasonography technique using Paine's point as a sonographic window provides useful and reliable diagnostic information on the causes of the brain swelling, enabling the neurosurgeon to select appropriate intraoperative management.