What is Herpes Encephalitis?

Human head and brain
Human head. Coloured composite image of a magnetic resonance imaging (MRI) scan of the brain and 2D and 3D computed tomography (CT) scans of the head and neck of a 35 year old patient. Zephyr/Science Photo LIbrary/Getty Imges

The viruses that cause genital herpes, oral herpes, and chicken pox usually cause sores and symptoms that are relatively benign. However, in rare cases, these viruses can infect the central nervous system and brain, which can potentially lead to encephalitis. In fact, herpes viruses have been shown to be the most common cause of infectious encephalitis. Fortunately, herpes viral encephalitis is also the only viral encephalitis with a widely available, and effective, treatment.

  known to have an effective cure.

Herpes encephalitis is a swelling and inflammation of the brain that can lead to symptoms including:

  • Fever

  • Headache

  • Mental Health/Behavioral Changes

  • Seizures

  • Vomiting

  • Weakness/Paralysis of Isolated Body Parts

  • Memory loss

One of the reasons that doctors are so concerned about herpes infections during pregnancy is that neonatal herpes infections are more likely to lead to serious complications such as encephalitis. If caught in a timely manner, these infections can usually be treated with large doses of herpes medications. However, in some infants, they can be fatal.

Encephalitis and other herpes infections of the central nervous system (CNS) are not only problems for infants. Although they have long been thought to be less common in adults, they can occur, particularly in people whose immune systems are compromised by HIV or other conditions, and there is some evidence that these infections may cause long-term cognitive deficits in some infected individuals.

Thanks to the development of new methods of detecting herpes viruses, there is also a growing body of literature suggesting that CNS herpes infections are more common than had been previously thought.

In addition to encephalitis, herpes infections have tentatively  been associated with several other brain conditions.

One of the associations that have gotten a lot of studies is the potential link between herpes simplex virus 1 infections and Alzheimer's disease. A number of studies have been published which show that the virus may interact with genetic factors to increase the risk of developing this form of dementia. There is also research suggesting that prenatal exposure to herpes simplex virus 2 may increase a child's risk of developing schizophrenia in the future. (However, it is important to note that HSV-2 is not the only virus for which prenatal exposure has been tentatively linked to risk of schizophrenia.)

Sources:

Arias I, Sorlozano A, Villegas E, de Dios Luna J, McKenney K, Cervilla J, Gutierrez B, Gutierrez J. Infectious agents associated with schizophrenia: a meta-analysis. Schizophr Res. 2012 Apr;136(1-3):128-36. doi:10.1016/j.schres.2011.10.026.

Fruchter E, Goldberg S, Fenchel D, Grotto I, Ginat K, Weiser M. The impact of Herpes simplex virus type 1 on cognitive impairments in young, healthy individuals - A historical prospective study. Schizophr Res. 2015 Sep 8. pii: S0920-9964(15)00465-X. doi: 10.1016/j.schres.2015.08.036.

Grahn A, Studahl M. Varicella-zoster virus infections of the central nervous system - Prognosis, diagnostics, and treatment. J Infect. 2015 Sep;71(3):281-93. doi: 10.1016/j.jinf.2015.06.004

Itzhaki RF, Wozniak MA. Herpes simplex virus type 1 in Alzheimer's disease: the enemy within. J Alzheimers Dis. 2008 May;13(4):393-405

Khandaker GM, Zimbron J, Lewis G, Jones PB. Prenatal maternal infection, neurodevelopment and adult schizophrenia: a systematic review of population-based studies. Psychol Med. 2013 Feb;43(2):239-57. doi: 10.1017/S0033291712000736.

Stahl JP, Mailles A, Dacheux L, Morand P. Epidemiology of viral encephalitis in 2011. Med Mal Infect. 2011 Sep;41(9):453-64. doi: 10.1016/j.medmal.2011.05.015.

Whitley R. Neonatal herpes simplex virus infection. Curr Opin Infect Dis. 2004 Jun;17(3):243-6.

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