Transient supranuclear paresis of the abduction in viral encephalitis of the brainstem

The supranuclear paresis of the abducens system, also known as posterior internuclear ophthalmoplegia of abduction, is a very rare disorder clinically characterized by unilateral or bilateral abduction paresis sometimes associated with nystagmus of the contralateral adducting eye, slowing of abduction saccades, and intact horizontal vestibulo-ocular reflex. Here, we report a 35-year-old woman who presented transient left side abduction deficit in conjunction, as the only symptom of self-limited viral encephalitis of the brainstem. Brain MRI including DWI and ADC maps showed an area of abnormal signal intensity in the mid-right ponto-mesencephalic junction. PCR analysis of cerebrospinal fluid showed an enterovirus infection. Spontaneous clinical recovery rapidly occurred 2 days after onset. The brainstem lesion was undetectable at 5-week brain MRI follow-up.