A Rare Case of Posterior Fossa Decompression Performed during Pregnancy for Chiari Malformation Type I.

Chiari malformation type I poses significant challenges during pregnancy, particularly among patients who present with severe or progressive neurological symptoms. Due to the rarity of the condition, clear management guidelines during pregnancy are lacking. Surgical intervention is generally deferred until the postpartum period. We report the case of a woman in her early 30s who presented with a 6-month history of severe downbeat nystagmus and cough-induced headaches. Magnetic resonance imaging revealed the presence of a 27-mm descent of the cerebellar tonsils and a small syrinx, with features consistent with Chiari malformation type I. She was found to be pregnant shortly after the diagnosis. Considering the severity of her symptoms and the surgical risks during the third trimester, posterior fossa decompression with duraplasty was performed at 15 weeks' gestation. The procedure was uneventful, and her headaches improved postoperatively. No neurological deterioration was observed during labor, and she delivered a healthy infant via spontaneous vaginal delivery. This case represents a rare instance of posterior fossa decompression for Chiari malformation type I performed during pregnancy. The favorable outcome highlights the potential safety and efficacy of second-trimester surgical intervention in select cases. We hope that this report will aid clinicians in making informed decisions regarding treatment timing for pregnant patients with symptomatic Chiari malformation type I.