CCD is a phenomenon of altered metabolism, blood flow, and function of the cerebellar hemisphere due to damage of the contralateral cerebral hemisphere. It is known to occur in acute strokes, tumors, and in refractory seizures. Acute CCD is a rare phenomenon in status epilepticus and has been described as asymptomatic and reversible, detected by PET, SPECT, and, rarely, MRI imaging.  Clinically significant CCD is even more rare and, to our knowledge, has never been described to lead to malignant edema.

We aimed to describe the first case of acute crossed cerebellar diaschisis (CCD) leading to cerebellar edema and herniation necessitating surgical decompression.

We described a clinical case and performed a PubMed review of available literature.

A 34-year-old male with a history of a blast injury to the head status-post hemicraniectomy with left frontoparietal encephalomalacia who was recovering well when he presented following 30 minutes of seizure requiring intubation. Exam revealed loss of brainstem reflexes and was concerning for early herniation. Head CT revealed new hypodensities in the left cerebral hemisphere as well as throughout the right cerebellum.  There was significant mass effect secondary to the cerebellar hypodensity leading to effacement of the fourth ventricle and upward herniation. This was at first mistakenly thought to be due to multifocal acute ischemic infarcts. Posterior fossa decompressive craniectomy with extra-ventricular device placement were performed emergently. Follow-up MRI revealed T2/FLAIR hyperintensities in the left cerebrum and right cerebellar hemisphere spanning multiple vascular territories consistent with crossed cerebellar diaschisis and vasogenic edema rather than acute infarction, as initially thought. On follow-up imaging several months later, these imaging findings resolved.

This case highlights acute CCD as a radiographic stroke mimic on CT and, to our knowledge, a novel cause of malignant cerebellar edema.