Unusual subacute diencephalic edema associated with a trapped fourth ventricle: Resolution following foramen magnum decompression

Introduction: A 4-year-old girl with a ventriculoperitoneal shunt presented to us with complaints of ataxia and altered consciousness. These symptoms were subacute at onset and progressive in nature. Case report: Radiological evaluation revealed a trapped fourth ventricle with brainstem compression, associated with abnormal diffuse diencephalic signal changes compatible with edema. The entrapment was managed by foramen magnum decompression, resulting in complete symptom resolution and improvement in the abnormal magnetic resonance findings. Discussion: While trapped fourth ventricle is a well-described entity, we could not find a similar reported case where such an acute clinical syndrome was associated with such a distinct radiological picture. Conclusions: In this paper, we review the pre-morbid history, clinical syndrome, and imaging. We then discuss possible mechanisms, their implications on decision-making, and the preferred modes of treatment.