Bilateral Transient Dilated and Fixed Pupils After Microvascular Decompression: Rare Clinical Experience.

Microvascular decompression (MVD) has a satisfactory safety, and it is the only surgical treatment for neurovascular compression diseases, such as hemifacial spasm, trigeminal neuralgia, and glossopharyngeal neuralgia, from the perspective of etiology. Bilateral dilated and fixed pupils have long been regarded as a sign of life threatening, which is common in patients with cerebral herniation due to cranial hypertension. However, transient dilated pupils after MVD have not been previously reported. Here, we presented 2 patients with bilateral transient dilated and fixed pupils after MVD and discussed the possible etiologies through the literature review. Physical examination of both patients showed bilateral pupils were normal and without a medical history of pupil dilation. They underwent MVD under general anesthesia and used propofol and sevoflurane. In both cases, the vertebral artery was displaced, and Teflon pads were inserted between the vertebral artery and the brain stem. Postoperation, we found transient bilateral mydriasis without light reflection in both patients. The emergency head computed tomography revealed no obvious signs of hemorrhage and cerebral herniation. About 1 hour later, this phenomenon disappeared. Therefore, the authors think if MVD is successfully carried out, bilateral transient mydriasis may not necessarily indicate brain stem hemorrhage, cerebral herniation, and other emergency conditions, which can be recovered within a short time. The causes could be related to stimulation of the sympathetic pathway in the brain stem during MVD and side effects of anesthetics.