An Ominous Finding: Cerebellar Reversal Sign

A 4-year-old boy presented with 5 days history of fever and vomiting. On day 4 of illness, he had one episode of generalized motor seizure, lasted for 20 minutes followed by altered sensorium. There was no history of ear discharge, rashes, and loose stools. On examination, he was febrile, had bradycardia and hypertension. He was comatose, had bilateral nonreactive and dilated pupils, bilateral grade 2 papilledema, and absent doll's eye response. A clinical possibility of acute encephalitis syndrome was kept and he was initiated on mechanical ventilation and other supportive measures. His computed tomography (CT) scan of the head showed poorly differentiated gray–white matter, hyperdense basal ganglia, thalamus, and cerebellum with subtle leptomeningeal contrast enhancement ([Fig. 1]). The child succumbed to his illness at 20 hours of admission.

Fig. 1 CECT of the head. Axial sections (A, B) of CECT brain showing poor gray–white matter differentiation, relatively lower attenuation of white matter as compared with gray matter, obliteration of prepontine cisterns and hyperdense basal ganglia, thalamus, and cerebellum (reversal sign). Note is made of subtle leptomeningeal contrast enhancement. CECT, contrast-enhanced computed tomography.

The reversal sign also called as white cerebellum or dense cerebellar sign and it is a description of attenuation relationship between gray and white matters. The white matter has relatively higher attenuation as compared with adjacent gray matter. The attenuation of basal ganglia, thalamus, brain stem, and cerebellum is also increased.[1] The underlying pathophysiology of this sign is preserved posterior circulation due to rich blood supply as compared with anterior circulation that may cause relatively preserved attenuation of posterior and central structures on CT. Distention of deep medullary veins by incomplete obstruction of venous outflow secondary to raised intracranial pressure is another contributory mechanism.[2] [3] This sign can be seen in severe hypoxic-ischemic encephalopathy, acute cerebellitis,[4] traumatic head injury, status epilepticus, and various infectious and inflammatory disorders of the central nervous system. For white cerebellar sign, contrast CT is not required, and it can be seen in native CT (i.e., without contrast). The reversal sign carries a poor prognosis and mortality rates are up to 35%.[2] The majority of the survivors have a severe neurodevelopmental deficit. Recognition of this sign is important on CT as lumbar puncture may cause downward herniation due to the pressure difference between supra- and infratentorial compartments.

Declaration on Competing Interest

Nil.

Publication History

Received: 15 September 2019

Accepted: 05 October 2019

Article published online:
28 February 2020

• References

• 1 Kavanagh EC. The reversal sign. Radiology 2007; 245 (03) 914-915
• 2 Han BK, Towbin RB, De Courten-Myers G, McLaurin RL, Ball Jr WS. Reversal sign on CT: effect of anoxic/ischemic cerebral injury in children. AJR Am J Roentgenol 1990; 154 (02) 361-368
• 3 Chalela JA, Rothlisberger J, West B, Hays A. The white cerebellum sign: an under recognized sign of increased intracranial pressure. Neurocrit Care 2013; 18 (03) 398-399
• 4 Sharawat IK, Kesavan S, Subramani V, Vyas S, Sahu JK, Saini L. Unusual cause of White Cerebellum. Indian J Pediatr 2018; 85 (07) 591-592