Cerebellum-Predominant Progressive Multifocal Leukoencephalopathy: An Under-recognized Cause of Cerebellar Syndrome among People with Human Immunodeficiency Virus Infection

Progressive multifocal leukoencephalopathy (PMLE) is caused by severe cortical demyelination due to reactivation of the polyomavirus, JC virus in profound immunosuppression, like advanced HIV infection. Cerebellum-predominant PMLE is rare and underreported. We report seven patients with confirmed cerebellum-predominant PMLE from a quaternary care center in South India over a five-year period. We report their outcomes and disability using modified Rankin scores (mRS). All seven patients had advanced HIV infection with low CD4 counts [median (IQR) 79 (51-155) cells/μL]. Ataxia (5/7; 71.4%), dysarthria (4/7; 57.1%), and vertigo (2/7; 28.5%) were the common symptoms at presentation. Cerebellar hemisphere or cerebellar peduncles with or without brainstem involvement were noted in all patients. Concomitant supratentorial involvement was also present in six patients. 'Shrimp sign' was seen in five of the seven patients. Only one patient had significant neurological recovery on follow-up. Cerebellum predominant PMLE is a severe, disabling opportunistic infection among patients with advanced HIV infection.