Transient Bilateral Fixed Dilated Pupils Following Papaverine Use During Intracranial Microvascular Decompression: A Case Report.

Fixed dilated pupils at the end of neurosurgical procedures are typically considered an ominous sign, often indicating acute brain injury, brainstem compression, or herniation, and are associated with poor neurological outcomes. However, pharmacological causes must also be considered. Papaverine hydrochloride, a vasodilator commonly used during intracranial surgery for the management of cerebral vasospasm, has been rarely reported to cause transient pupillary dilation and fixation. We describe the case of a 48-year-old woman with hemifacial spasm who underwent retrosigmoid craniotomy and microvascular decompression of the left facial nerve. The intraoperative course was uneventful under total intravenous anesthesia. Papaverine (200 mg) was locally infiltrated to relieve vasospasm of the anterior inferior cerebellar artery. At the conclusion of surgery, bilateral fixed dilated pupils (7 mm, nonreactive) were observed, raising concern for catastrophic intracranial pathology. Urgent neuroimaging was planned. However, within 15 minutes, the patient developed spontaneous respiratory effort, responded to commands, and her pupils returned to normal size and reactivity. She was extubated uneventfully and subsequently made a complete recovery, being discharged home on postoperative day 6. This case highlights a rare but important confounding effect of papaverine infiltration during neurosurgery. Papaverine may induce transient mydriasis mimicking signs of devastating neurological injury. Awareness of this phenomenon is critical for anesthesiologists, neurosurgeons, and critical care teams to avoid unnecessary interventions and guide appropriate postoperative decision-making.