Visual impairment associated with direct compression of the visual cortex due to subdural hematoma following foramen magnum decompression: illustrative case.

backgroundPostoperative subdural hematoma (SDH) typically presents with headache, impaired consciousness, hemiplegia, gait disturbance, and aphasia but can also present with visual impairment. OBSERVATIONS: A 52-year-old woman diagnosed with Chiari malformation type I and syringomyelia underwent foramen magnum decompression. Cerebrospinal fluid was lost due to arachnoid injury during the procedure. Postoperatively, a small acute SDH was apparent in the posterior convexity on head computed tomography but was managed conservatively because no neurological deficits were present. Visual impairment developed 2 weeks postoperatively. Ophthalmological examination showed right lower quadrantanopia with normal anterior ocular segment and fundoscopic findings. Magnetic resonance imaging demonstrated SDH in the left posterior convexity with direct compression of the visual cortex. Conservative treatment reduced the hematoma and improved visual impairment. LESSONS: SDH in the posterior convexity can cause visual impairment via direct compression of the visual cortex. SDH should be included in the differential diagnosis for patients presenting with visual impairment following craniotomy. https://thejns.org/doi/10.3171/CASE24525.