Unveiling the hidden danger: a rachnoid cyst in the fourth ventricle: a rare case report and review of the literature.

Arachnoid cysts are benign CSF-filled sacs that commonly develop in the regions of the Sylvian fissure and cerebellopontine angle. Their occurrence in ventricles especially in the fourth ventricle is rare. These cysts can have a gamut of neurological symptoms. Surgical intervention is usually required to manage symptomatic cysts. A 55-year-old man presented with occipital headaches for 6 months, followed by increasing lower limb weakness, gait abnormalities, and cognitive impairments. Investigations revealed a cyst in the fourth ventricle extending into the foramina of Luschka, causing obstructive hydrocephalus, 8 mm tonsillar herniation, and brainstem compression. The surgical procedure involving a midline suboccipital craniotomy, cyst decompression, removal of adhering walls, and restoration of cerebrospinal fluid flow was performed, leading to the restoration of neurological functions. Arachnoid cysts can cause neurological symptoms as a result of pressure exertion on adjacent brain structures. Symptoms such as cognitive impairment, limb weakness, and obstructive hydrocephalus can occur due to the presence of fourth ventricular cysts, which are a rarity. The standard approach for managing a symptomatic cyst is surgical removal, which aims to relieve pressure and restore cerebrospinal fluid flow. Postoperative monitoring is essential to reduce the risk of recurrence and development of complications. The presence of an arachnoid cyst should be considered in atypical locations like the fourth ventricle in adults presenting with progressive neurological deficits. Timely surgical intervention is critical for symptom relief and avoiding complications. Long-term monitoring remains critical for detecting recurrence or treatment failure.