Chiari type 1 malformation in a pseudotumour cerebri patient: is it an acquired or congenital Chiari malformation?

Chiari malformation type 1 (CM1) is a developmental abnormality of the cerebellar tonsils. Patients with CM1 commonly present with headache. Papilloedema is rarely seen in CM1. However, a 52-year-old woman presented to the hospital with a headache and her ophthalmological examination revealed bilateral papilloedema. Her cranial MRI was compatible with borderline CM1. Bilateral papilloedema and headache suggested idiopathic intracranial hypertension (IIH) as the preliminary diagnosis. IIH is a rare case in CM1. This article argues about this association and discusses as to whether it is an acquired or congenital Chiari malformation.