An 85-year-old man underwent emergency right trepanation and drainage for a symptomatic chronic subdural hematoma. Pseudohypoxic brain swelling (PHBS) was suspected because magnetic resonance imaging revealed diffuse brain swelling. Although cerebrospinal fluid (CSF) leakage was not obvious during or after surgery, most of the reported PHBS cases have leaked CSF during craniotomy or spine surgery. PHBS has not been previously reported in patients without obvious CSF leakage or after unilateral burr hole drainage. Herein, we report an extremely rare case with a literature review investigating its pathogenesis and clinical features.