Progressive Quadriparesis of a Toddler with a Posterior Cranial Fossa Arachnoid Cyst (AC): Illustrative Case Report and Narrative Literature Review

Background/Objectives: Intracranial arachnoid cysts (ACs) may be congenital, primary, or secondary due to trauma. These cysts are benign, contain cerebrospinal fluid (CSF), and are classified based on location, size, and their clinical symptomatology. They are uncommon lesions in children, rarely leading to severe mass-effect neurological symptomatology. Methods: The present report describes a 30-month-old female presenting with quadriparesis. An emergency magnetic resonance imaging (MRI) study revealed the presence of a primary intracranial arachnoid cyst of the posterior cranial fossa, exerting significant pressure on the medulla oblongata and the cervical portion of the spinal cord, displacing them dorsally, with a remnant diameter of 2.5 mm. Results: This benign malformation located in a crucial area might have been complicated by severe neurological deterioration and required prompt intervention, so the patient underwent a suboccipital craniectomy in a sitting position, along with a neurosurgical procedure, which established a lasting communication channel between the cyst and the basal cisterns. This led to a favorable outcome. Conclusions: Up to the present report, postoperative complete resolution of quadriparesis secondary to a posterior cranial fossa arachnoid cyst has not been reported. At present, no therapeutic modality has been established as the definitive standard of care for pediatric ACs, and their management raises a great deal of controversy among neurosurgeons. The narrative literature review of the present study integrates the various perspectives regarding ACs and their possible treatment approaches that are currently available.