"Dangling choroid" with contralateral glomus displacement and ischemic torsion in congenital hydrocephalus: illustrative case.

background"Dangling choroid" is a prenatal sonographic marker of ventriculomegaly that measures the angle of choroid plexus (ChP) displacement in the lateral ventricle. To the authors' knowledge, postnatal sequelae related to this pathology, besides hydrocephalus, have never been reported. OBSERVATIONS: A female fetus was diagnosed with bilateral ventriculomegaly. Postnatally, the patient was diagnosed with hydrocephalus and macrocephaly secondary to aqueductal stenosis and underwent endoscopic third ventriculostomy with ChP cauterization. Intraoperatively, the septum pellucidum was incomplete, and the right-sided ChP glomus was contralaterally displaced and entangled with the left, with evidence of ischemic torsion and hemorrhage. LESSONS: In this case of an ischemic ChP secondary to transventricular displacement of the glomus, at least two biomechanical events are relevant. First, the choroid fissure and velum interpositum can be thinned in the setting of ventriculomegaly. Second, stretching and perforation of the septum pellucidum can occur. Both changes can increase the mobility of a dangling choroid, occasionally leading to entanglement of the vascular pedicles. Preoperative recognition of this complication can help optimize surgical planning, e.g., using flexible endoscopy to facilitate complete ChP cauterization and changing the surgical approach if the ChP has been displaced. https://thejns.org/doi/10.3171/CASE24505.