Reversible diencephalic edema in trapped fourth ventricle: a diagnostic and therapeutic marker and reversal by aqueductoplasty

Abstract

Dear Editor,Diagnosis and treatment schemes in a trapped fourthventricle have always been a dilemma, especially in infantsand in children with poor neurological baseline.In our previous article [1] on trapped fourth ventricle, wehad reported the occurrence of diencephalic edema inassociation with trapped fourth ventricle and had demon-strated its disappearance following foramen magnumdecompression. We had also observed that this sign mightrepresent a diagnostic sign to the trapped nature of thefourth ventricle [1]. We provide further material in supportof this concept, albeit with a few essential differences.We came across a 3-month-old prematurely born infant,who had a ventriculoperitoneal shunt (VPS) post-intraventricularhemorrhage.Hepresentedtouswithahistoryof insertion of VPS and removal secondary to shunt-relatedmeningitis. Clinically, the infant had sunset eyes, a fullanterior fontanelle, ophisthotonus, and a feeble cry.His MRI revealed dilated ventricles with multipleloculations and an enlarged fourth ventricle. The enlargedfourth ventricle was associated with a sign of brainstemcompression and transtentorial herniation. The T2-weightedsequences showed hyperintense signal changes in thediencephalon (Fig. 1). As the issue of meningitis was notsolved, we resorted to endoscopic fenestration of theloculations and an aqueductoplasty to relieve the trappedfourth ventricle. For the hydrocephalus, we continued to taphis lateral ventricles whenever the fontanelles were bulgingand the child symptomatic. The infant subsequentlyunderwent a VPS post-adequate antibiotic therapy.Postoperative MRI, 2 weeks after the aqueductoplastywhile the infant was awaiting a definitive CSF diversion,showed resolution of the signal changes in the diencepha-lon (Fig. 2). Notably, this was in present persistenthydrocephalus and signal changes elsewhere.As detailed in our previous article, the diencephalic/peri-fourth ventricular (transtentorially herniating fourth) signalchanges appeared to be secondary to pressure elevationwithin the entrapped fourth ventricle and a secondaryincrease in tissue water content [1]. Edema can occur at theareas of highest ventricular concavity, greatest expansivestress, and ependymal damage [2–4]. Additionally, vascularcompromise secondary to raised pressure, especially in the