Brainstem involvement in neonatal herpes simplex virus type 2 encephalitis

Herpes simplex virus encephalitis in the newborn typically involves the cerebral cortex in a widespread manner. Herpes simplex virus type 2 rarely involves the brainstem. Here we report a 16-day-old infant with predominant brainstem and cerebellar involvement secondary to herpes simplex virus type 2 infection. Diffusion-weighted MRI performed 3 days after the onset of symptoms revealed restricted diffusion mainly in brainstem and cerebellar structures. No abnormal findings were seen on conventional MRI. Subsequent MRI scans showed evolution of the brain injury with extension along the corticospinal tracts. However, there was no evidence of any other supratentorial gray or white matter injury. This is the first report of predominant brainstem involvement in neonatal herpes simplex virus type 2 encephalitis. In addition, the importance of performing diffusion-weighted sequences to detect early central nervous system involvement and serial MRI to follow the evolution of central nervous system lesions is emphasized.