Surgery for infratentorial lesions requires more meticulous care than that for supratentorial lesions1–3 because the cerebellum is easily damaged as it is softer than the cerebral cortex. Moreover, the brain stem is located and vessels and cranial nerves are distributed in a narrow space. Such drawbacks are mitigated when the dura mater is opened and the lateral cerebellopontine cistern or lateral cerebellomedullary cistern is punctured with cerebellar retraction for drainage of cerebrospinal fluid (CSF).1,3–5 This procedure decreases the pressure of the posterior fossa and facilitates access to lesions.
However, CSF in some patients is difficult to drain because fulminant cerebellar swelling occurs after incising the dura mater. In addition, in these patients, excessive cerebellar retraction for drainage of CSF is attempted, which could induce unexpected cerebellar injury. For that reason, we usually drain CSF by puncture of the horizontal fissure (HF) of the cerebellum to prevent cerebellar injury in our institution. Then, decompression of the posterior fossa is easily accomplished. This procedure can produce good operative views without excessive cerebellar retraction.
We evaluated the value of this surgical method through quantitative analysis of the volume of CSF drained by HF puncture. We also estimated the position of HF on the dura mater.
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