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Given the abundance of vital neurovascular structures, gunshot wounds (GSWs) to the posterior fossa are generally fatal. We present a unique such case where a bullet entered the petrous bone, traversed the cerebellar hemisphere and overlying tentorial leaflet, and reached the dorsal aspect of the midbrain, resulting in transient cerebellar mutism with an unexpectedly favorable functional recovery. A 17-year-old boy sustained a GSW to the left mastoid region with no exit wound and presented with agitation and confusion, ultimately leading to a coma. Head CT revealed a bullet trajectory through the left petrous bone, left cerebellar hemisphere, and left tentorial leaflet, with a retained bullet fragment in the quadrigeminal cistern, overlying the dorsal aspect of the midbrain. Computed tomography venography (CTV) demonstrated thrombosis of the left transverse and sigmoid sinuses and the internal jugular vein. The patient's hospital course was marked by the development of obstructive hydrocephalus, secondary to delayed cerebellar edema with fourth ventricular effacement and aqueductal compression, possibly worsened by concomitant left sigmoid sinus thrombosis. Following the emergency placement of an external ventricular drain and two weeks of mechanical ventilation, the patient's level of consciousness improved significantly, with excellent brainstem and cranial nerve function, ultimately leading to successful extubation. Although the patient exhibited cerebellar mutism secondary to his injury, his cognitive abilities and speech improved significantly during rehabilitation. At his three-month outpatient follow-up, he was ambulatory, independent in his daily living activities, and able to verbally communicate using full sentences. Though exceptional, survival and functional recovery may occur after a GSW to the posterior fossa. A basic understanding of ballistics and the importance of biomechanically resilient anatomic barriers, such as the petrous bone and tentorial leaflet, can help predict a good outcome. Lesional cerebellar mutism tends to have a favorable prognosis, especially in young patients with central nervous system plasticity.

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OBJECTIVE The predictors of survival and functional recovery following emergency decompressive surgery in patients with transtentorial brain herniation, particularly those with pupillary abnormalities, have not been established. In this study, the authors aimed to assess the outcome of patients with intracranial mass lesions, transtentorial brain herniation, and nonreactive mydriasis, following emergency surgical decompression. METHODS A retrospective chart review was performed of all patients with transtentorial herniation and pupillary abnormalities who underwent craniotomy or craniectomy at two trauma and stroke centers between 2016 and 2022. The functional outcome was determined using the modified Rankin Scale (mRS). RESULTS Forty-three patients, 34 men and 9 women with a mean age of 47 years (range 16–92 years), were included. The underlying etiology was traumatic brain injury in 33 patients, hemorrhagic stroke in 8 patients, and tumor in 2 patients. The median preoperative Glasgow Coma Scale score was 3 (range 3–8), and the median midline shift was 9 mm (range 1–29 mm). Thirty-two patients (74.4%) had bilaterally fixed and dilated pupils. The median time to surgery (from pupillary changes) was 133 minutes (mean 169 minutes, range 30–900 minutes). Eighteen patients (41.9%) died postoperatively. After a median follow-up of 12 months (range 3–12 months), 11 patients (26.8%) had a favorable functional outcome, while 10 remained severely disabled (mRS score 5). On univariate analysis, younger age (p < 0.001), less midline shift (p = 0.049), and improved pupillary response after osmotic therapy (p < 0.01) or decompressive surgery (p < 0.001) were associated with favorable outcomes at 3 months. CONCLUSIONS With aggressive medical and surgical management, patients with transtentorial brain herniation, including those with bilaterally fixed and dilated pupils, may have considerable rates of survival and functional recovery. Young age, less midline shift, and improved pupillary response following osmotic therapy or decompressive surgery are favorable prognosticators.