Background: Idiopathic intracranial hypertension (IIH) and Chiari I malformation (CMI) may present with overlapping symptoms and imaging findings, including cerebellar tonsillar descent, making accurate diagnosis challenging. This case illustrates the diagnostic complexity and highlights the role of venous sinus stenosis as an underlying etiology in IIH. Case Description: We present the case of a 65-year-old obese woman with a history of CMI previously treated with suboccipital decompression. She re-presented with recurrent headaches, diplopia, and left upper extremity paresthesia. Imaging revealed tonsillar descent and a cervical syrinx. She underwent revision decompression with duraplasty. Despite initial improvement, she developed worsening headaches, hydrocephalus, and posterior fossa subdural hygromas. Magnetic resonance venography revealed bilateral transverse-sigmoid sinus stenosis, prompting consideration of venous sinus stenting. Cerebral venography demonstrated significant pressure gradients across bilateral transverse-sigmoid junctions. The patient underwent successful bilateral venous sinus stenting, resulting in improved venous outflow and resolution of elevated pressure gradient across the venous sinus stenoses. Postoperatively, her headaches resolved, and her acetazolamide dosage was gradually reduced. Follow-up imaging showed resolution of hydrocephalus and subdural collections. At 1-year follow-up, her preoperative symptoms had significantly improved. Conclusion: This case highlights the importance of considering IIH and venous sinus stenosis in patients with persistent or recurrent symptoms after Chiari decompression. Accurate diagnosis using cerebral venography is essential to guide appropriate treatment. Venous sinus stenting can provide durable symptom relief in select patients with IIH mimicking CMI.
Shoap et al. (2026) studied this question.