Neonatal herpes simplex encephalitis

Neonatal herpes simplex encephalitis is caused by vertical transmission of infection infection during passage from birth canal with diffuse cerebral involvement within the first month after birth; in contrast to adult herpes simplex encephalitis, it is commonly related to HSV-2. 

Epidemiology

The incidence of neonatal HSV infection at all is usually low and it varies by country. About 80% of cases are due to HSV type II. 

Clinical presentation

There are three types of clinical manifestations related to this infection ²:

• skin lesions without any visceral or central nervous system (CNS) involvement, also known as skin, eye and mouth disease disease
• CNS disease (with or without skin lesions, but without involvement of visceral organs). Usually; usually this presentation has non non-specific signs including decreased level of consciousness, seizures, lethargy and fever
• disseminated form characterizedcharacterised as a sepsis with sepsis with multi-organ failure 

Newborn babies are initially asymptomatic for one or two weeks.

The diagnosis is confirmed by detection detection of HSV DNA in the the cerebrospinal fluid.

Radiographic features

It is important to appreciate that the radiographic appearance of neonatal HSV encephalitis is different from its more common adult counterpart. 

Changes are typically diffuse which which can be difficult to identify due to normal immature myelin (seenormal myelination). The medial temporal and inferior frontal lobes may be spared and haemorrhagic change is uncommon but can develop later and best seen on T2* sequences¹. Calcification and migrational anomalies are typically absent.

Approximately half of the patients show restrictionRestriction diffusion on DWI whichis demonstrated in approximately half of all patients, which tends to be diffuse and bilateral.

Treatment and prognosis

Neonatal herpes simplex encephalitis is is highly lethal (in about 50% of cases) and can cause permanent cause permanent disability if left untreated ². 

Treatment is with intravenous antivirals (aciclovir is usually usually the drug of choice).  

Sequelae are mostly mostly seen in neurodevelopment, including deafness, vision loss, cerebral palsy, and seizure.