Table 2:

Neurologic syndromes associated with John Cunningham virus infection

Phenotype	Clinical features	MRI appearance
Classic PML	Supratentorial lesions: hemiparesis, hemisensory loss, seizures, encephalopathy Infratentorial lesions: cranial neuropathies, cerebellar signs including ataxia and dysarthria	T1 hypointense lesions, T2 and FLAIR hyperintense lesions in subcortical white matter. Nonenhancing. May have perilesional diffusion restriction.
Inflammatory PML	Acute aggravation of symptoms in a patient with classic PML	Rim-enhancing lesions, which may be associated with vasogenic edema and mass effect
JCV meningitis	Fever, meningism, photophobia	No specific imaging findings
JCV encephalopathy	Confusion, reduced level of consciousness, aphasia, progressive cognitive impairment	Cortical grey matter T2 hyperintensities, spreading to white matter in the late stages of disease
JCV granular cell neuronopathy	Cerebellar signs including ataxia and dysarthria	Isointense cerebellar atrophy with T2 hyperintensities in the late stages of disease

Note: FLAIR = fluid-attenuated inversion recovery sequence, JCV = John Cunningham virus, MRI = magnetic resonance imaging, PML = progressive multifocal leukoencephalopathy.