Sunset Sign Due to Intraventricular Tension Pneumocephalus: A Key Clue to Evaluating Delayed Emergence After General Anesthesia

Prompt emergence from general anesthesia is crucial after neurosurgical procedures, such as craniotomies, to facilitate timely neurological evaluation for identification of intraoperative complications. Delayed emergence can be caused by residual anesthetics, metabolic imbalances, and intracranial pathology, for which an eye examination can provide early diagnostic clues. The sunset sign (or setting sun sign), characterized by a downward deviation of the eyes, can be an early indicator of raised intracranial pressure (ICP) or midbrain compression, as is commonly observed in states of hydrocephalus or periaqueductal or tectal plate dysfunction. A 50-year-old woman with a history of headaches, diplopia, and Parinaud syndrome presented with a pineal mass and underwent an occipital and suboccipital craniotomy with endoscopically-assisted tumor resection. The procedure was managed with neurophysiological monitoring to detect surgical compromise on neurophysiological function. An external ventricular drain (EVD) was placed for cerebrospinal fluid (CSF) drainage to facilitate brain relaxation and operative intervention. Blood loss was estimated to be 200 ml. Thirty minutes after surgery, the patient did not open her eyes to verbal commands despite the cessation of anesthetics significantly earlier. Eye examination revealed an intermittent downward gaze, recognized as the sunset sign. Arterial blood gas results and metabolic parameters were within normal limits, shifting the focus to possible intracranial complications as the source of her delayed emergence. Consequently, an emergent head computer tomography (CT) was ordered, and the EVD was clamped and not monitored for transport. The CT scan revealed tension pneumocephalus compressing the midbrain. The patient was transferred to the neurocritical care unit, where the admission ICP measured from the EVD was 50 mmHg. Initial critical care treatment included maintaining sedation, CSF drainage via the EVD, 100% oxygen, and head of bed at zero degrees. The patient underwent an MRI brain approximately six hours post-operatively, revealing restricted diffusion in the bilateral medial thalamic regions. The patient was successfully extubated on postoperative day one. Over the following 48 hours, the sunset sign disappeared, the tension pneumocephalus resolved, ICP normalized, and the patient's neurological status gradually improved. Delayed emergence after neurosurgical procedures can be multifactorial, and eye movement abnormalities like the sunset sign can offer early diagnostic clues. In this case, the sunset sign occurred from elevated ICP due to tension pneumocephalus, a rare but serious postoperative complication. Early recognition of the sunset sign and immediate neuroimaging allowed for prompt relief of intracranial hypertension, highlighting the importance of incorporating detailed ocular assessments into postoperative evaluations. The sunset sign is an important clinical marker of increased ICP and midbrain dysfunction, warranting urgent investigation. This case underscores the need for early, thorough postoperative assessment, including eye examination, to identify and manage potential complications that may delay emergence from general anesthesia. Eye examination may be warranted as part of routine neurological evaluation during emergence from general anesthesia.