Neonatal herpes simplex encephalitis
Neonatal herpes simplex encephalitis is caused by vertical transmission of 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.
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.
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
- CNS disease (with or without skin lesions, but without involvement of visceral organs); usually this presentation has non-specific signs including decreased level of consciousness, seizures, lethargy and fever
- disseminated form characterised as a sepsis with multi-organ failure
Newborn babies are initially asymptomatic for one or two weeks.
The diagnosis is confirmed by detection of HSV DNA in the cerebrospinal fluid.
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 can be difficult to identify due to normal immature myelin (see normal 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* sequences 1. Calcification and migrational anomalies are typically absent.
Restriction diffusion on DWI is demonstrated in approximately half of all patients, which tends to be diffuse and bilateral.
Treatment and prognosis
Neonatal herpes simplex encephalitis is highly lethal (in about 50% of cases) and can cause permanent disability if left untreated 2.
Treatment is with intravenous antivirals (aciclovir is usually the drug of choice).
Sequelae are mostly seen in neurodevelopment, including deafness, vision loss, cerebral palsy, and seizure.
- 1. Leonard JR, Moran CJ, Cross DT et-al. MR imaging of herpes simplex type 1 encephalitis in infants and young children: a separate pattern of findings. AJR Am J Roentgenol. 2000;174 (6): 1651-5. AJR Am J Roentgenol (full text) - Pubmed citation
- 2. Wolfert SI, de Jong EP, Vossen AC et-al. Diagnostic and therapeutic management for suspected neonatal herpes simplex virus infection. J. Clin. Virol. 2011;51 (1): 8-11. doi:10.1016/j.jcv.2011.02.008 - Pubmed citation
- 3. Vossough A, Zimmerman RA, Bilaniuk LT et-al. Imaging findings of neonatal herpes simplex virus type 2 encephalitis. Neuroradiology. 2008;50 (4): 355-66. doi:10.1007/s00234-007-0349-3 - Pubmed citation