Unusual association of cervical arachnoid cyst and idiopathic intracranial hypertension.

Arachnoid cysts (ACs) are more commonly seen intracranially rather than intraspinally, with most being asymptomatic. This case report presents a rare association between symptomatic AC and idiopathic intracranial hypertension (IIH). In a 71-year-old man who exhibited long-standing bilateral shoulder pain and severe left brachialgia despite an unremarkable physical examination. Radiologic investigations revealed a left C5-6 cervical arachnoid cyst, and during treatment, the patient was diagnosed with IIH. Surgical excision of the cyst failed, so the patient was treated with a lumbar puncture (LP) shunt that required several revisions. During these revisions, IIH was diagnosed, leading to the insertion of a ventriculoperitoneal (VP) shunt, which improved the symptoms. Early diagnosis of IIH through lumbar puncture in cases of spinal arachnoid cysts allows for earlier treatment with cerebrospinal fluid (CSF) diversion via a VP shunt, reducing repeated hospital admissions and surgical interventions.