Herpes Simplex Encephalitis HSE

Herpes Simplex  Encephalitis

            Author: Wayne E Anderson, DO; Chief Editor: Nicholas Y Lorenzo, MD


HSE (Herpes Simplex Encephalitis)

HSE (Herpes Simplex Encephalitis)  is the most common nonepidemic encephalitis. Incidence is 2 cases per million of population per year. HSE (Herpes Simplex Encephalitis) may occur year-round. HSV-1 is ubiquitous and HSV-2 is also common.


International incidence is similar to that in the United States.


HSV-1 and HSV-2 infections often recur. HSE rarely occurs. Untreated HSE is progressive and often fatal in 7-14 days. However, significant morbidity exists among those treated. A landmark study by Whitley et al in 1977 revealed a 70% mortality rate in untreated patients and severe neurologic deficits in most of the survivors.[2] The following demonstrate the variety of complications.

  • Elbers and colleagues followed properly treated children for 12 years after the HSE.
  • They found seizures in 44% of the children and developmental delay in 25% of the children.
  • They concluded that HSE (Herpes Simplex Encephalitis) continues to be associated with poor long-term neurologic outcomes despite appropriate therapy.[3]
  • Shelley and colleagues reported a case of intracerebral hematoma occurring in a patient successfully treated with a full course of acyclovir after apparent eradication of the virus. The hematoma occurred in the region of the encephalitis[4]


  • In HSE, patients may have a prodrome of malaise, fever, headache, and nausea.
  • This is followed by acute or subacute onset of an encephalopathy whose symptoms include lethargy, confusion, and delirium.

Headaches, seizures, aphasia, and other focal deficits also may occur.


  • On neurologic examination, global and focal neurologic findings include encephalopathy, delirium, aphasia, cranial nerve deficits, and hemiparesis.
  • Meningeal signs may be present.
  • Unusual presentations occur. Both HSV-1 and HSV-2 may produce a more subacute encephalitis, apparent psychiatric syndromes, and benign recurrent meningitis. Less commonly, HSV-1 may produce a brain stem encephalitis and HSV-2, a myelitis.
  • Consultations
  • HSE (Herpes Simplex Encephalitis)  is a neurologic emergency. Consultation with a neurologist is required.
  • Neurosurgical consultation is helpful only if a brain biopsy is being considered.
  • An infectious disease consultation may be appropriate.
  • An evaluation for rehabilitation is often appropriate to deal with the long-term neurological sequelae of HSE.


  • Common sequelae among survivors include motor deficits, seizure disorders, and changes in mental status.
  • If treatment of HSE (Herpes Simplex Encephalitis)  is delayed, permanent neurological deficits may occur in survivors.
  • Even in treated cases of HSE, complications and sequelae are not uncommon.
  • Both focal and global sequelae may occur, and survivors may require permanent assistance.
  • Cognitive and memory deficits are particularly common, as are recurrent seizures.
  • Prognosis
  • Anterograde memory often is impaired even with successful treatment of HSE.
  • Retrograde memory, executive function, and language ability also may be impaired. A study by Utley et al showed that patients who had a shorter delay (< 5 d) between presentation and treatment had better cognitive outcomes.[16]   

 Encephalitis Facts

  • Encephalitis is inflammation of the brain
  • Inflammation is usually caused by infection or an inappropriate auto-immune response to infection
  • The incidence is reported as 7.4/100,000 (based on US statistics)
  • Anyone can become ill with encephalitis, at any age
  • The inflammation can damage nerve cells resulting in “acquired brain injury”

Compared to other infectious diseases, encephalitis has a high mortality rate

Herpes Simplex Encephalitis


This paper was prepared by Dr Graham Cleator, Head, Division of Virology, Clinical Sciences Building,  Manchester Royal Infirmary
Revised by Dr Nick Davies, St Mary’s Hospital, London

The Illness

HSE (Herpes Simplex Encephalitis)is rare.  How HSV gains access to the brain is not known, but here are various hypotheses, Firstly, viruses may enter the brain from the blood stream.  To do this the virus must be small, present in large numbers and able to cross the blood/brain barrier (BBB). Taking into account the properties of the virus this is a possible but probably infrequent route of entry to the central nervous system (CNS).  Secondly, there is a direct route, via nerves, from the nose to the olfactory lobes of the brain.

The virus may “move “from its site of latency via nerves to the base of the skull, cross the meninges and infect the brain. There is however little evidence to support this suggestion. A further possibility is that the virus moves from its site of latency in the trigeminal ganglia ”backwards” to the spinal cord and then upwards into the brain. The appropriate nerve pathways exists to support this suggestion but to date there is no definite evidence to support this or indeed any of the other suggested routes.

Whichever way HSV- I gains access to the brain, in the acute illness, the damage that results from the viral infection and associated inflammation is often severe.  Early in infection, the virus shows a distinct predilection for certain parts of the brain.  Typically it is initially present in the limbic cortices. It may then spread to the adjacent frontal and temporal lobes.  It is the destruction of tissue in these areas together with brain swelling from the inflammation, which causes many of the symptoms associated with HSE.

HSE usually develops over a period of days but, like any other viral infection, depending, for example, upon the immunity of the patient, the disease may take a variable course.  Typically it begins with “flu-like” symptoms followed by neurological deterioration, which may include personality and behavioral changes, and perhaps fits and dysphasia.  If untreated it may lead to progressive impairment of consciousness, coma and death.


The rapid onset and development of HSE (Herpes Simplex Encephalitis)  presents a dilemma to the clinician.  During the early stages, when treatment would be most effective, the symptoms can be very general, so there may be several possible diagnoses.

Most hospitals do an EEG (an electro-encephalogram to monitor the brains electrical activity), plus brain imaging by a CT scan (computerized tomography), or, for a clearer picture, an MRI (magnetic resonance imaging). These procedures, together with careful and continuous clinical assessment provide data, which may be suggestive of HSE and, importantly, may exclude other conditions. However the diagnostic procedure now accepted as providing an etiological diagnosis of HSE is the polymerase chain reaction (PCR).  This is a test that has been developed using the methods of modern molecular biology.  The PCR is not used exclusively for the diagnosis of HSE but is also used in many other areas of research and diagnosis.  In principle of the test is simple (they always are when they have been developed!) but because the test is so sensitive great care must be exercised at all stages of the procedure.  The risk of producing false results is always present especially if suitable care and precautions are not taken during taking specimens and in the PCR laboratory.

The role of Acyclovir is central to the treatment of HSE. If therapy can be started during the first few days of the illness there is a dramatic reduction in the mortality rate – c.80% down to 25%..  The provision of high levels of nursing care and the management of complications such as brain edema (i.e. swelling) are also key factors, which may influence the outcome of HSE.  As experience with the use of Acyclovir has grown it has become apparent that the currently accepted 10 day course of treatment may not always be sufficient to provide effective treatment. Rare cases of “relapse” of encephalitic illnesses have and are being noted.

The reduction in mortality has led to a paradoxical situation. There are without doubt more survivors, but many may suffer from permanent neurological and/or psychological deficits, for example amnesia (memory loss).  For a child with a potentially long life ahead this is a particularly distressing situation.  Improvements are still needed in both diagnosis and treatment.

Recent recognition of mild cases of HSE (Herpes Simplex Encephalitis)  and the suggestion that latent infection of the brain can occur add a further dimension to this disease.  If a patient suffers repeated episodes of mild (undiagnosed and not debilitating) HSE (Herpes Simplex Encephalitis), there could be progressive damage to the brain.  The relationship of such episodes to the development of various psychological disorders must now be given serious consideration and form the basis of future research programs.

The message is that our understanding of conditions such as viral encephalitis is continually developing.  However, these are complex conditions and whilst it is unlikely that encephalitis will be preventable (in the foreseeable future) the prospect for the rapid and efficient diagnosis for many of these conditions will improve during coming years.  The consequence of improved and rapid diagnosis is that early treatment (which is so important) can and will increasingly be introduced.

29 Responses to Herpes Simplex Encephalitis HSE

  1. Vickie says:

    I would tell your daughter that the hermit crab wanted to tell her a special secret just for her and she wasn’t listening so he grabbed her ear to get her attention. He didn’t know his own strength so he hurt her by mistake. She would just have to be more care next time when a Hermit crab comes calling. Give her a wonderful positive story that she can tell her children someday about the sea shore and the hermit crab in his new home. Life is full of wonderful moments and memories for sharing. Thanks for sharing.
    Hope, Health, and Happiness,

  2. website zone says:

    Today, I went to the beachfront with my children. I found a sea shell and gave it to my 4 year old daughter and said “You can hear the ocean if you put this to your ear.” She put the shell to her ear and screamed. There was a hermit crab inside and it pinched her ear. She never wants to go back! LoL I know this is completely off topic but I had to tell someone!

  3. Thanks for sharing educational material on HSE. I’ve seen several patients die because the delay in diagnosis. It appears Marcus has a progressive HSE given his MRI results…but he’s still expected to function and understand his world around him while others are taking advantage of his situation and him. Prison is not the place for brain injured people, but Rehabilitation is! How is he going to learn to trust again in prison?

  4. Kyle Romero says:

    It is best to take part in a contest for among the finest blogs on the web. I’ll suggest this website!

  5. I simply want to mention I am just beginner to blogs and truly savored you’re blog. Almost certainly I’m going to bookmark your website . You actually come with very good articles. Appreciate it for sharing with us your blog site.

  6. Hannah Montagne says:

    Very nice post. I just stumbled upon your weblog and wished to say that I’ve truly loved surfing around your blog posts. In any case I will be subscribing for your rss feed and I hope you write once more soon!

  7. Pingback: carson

  8. Haessig99 says:

    Fanatically been searching almost almost everywhere on information regarding this. Actually thank you a lot.

  9. Pingback: liberty

  10. Ferdinand Alimento says:

    very nice put up, i actually love this web site, keep on it

  11. Devon Crall says:

    I like what you guys tend to be up too. This type of clever work and reporting! Keep up the fantastic works guys I’ve added you guys to my own blogroll.

  12. Giubbotti Belstaff says:

    I am without words. This is often a excellent website and incredibly alluring too. Good work! Which is no longer in reality a whole lot via a good beginner writer at all like me, nevertheless it surely’s almost all I could merely point out right after snorkeling into your content. Excellent sentence structure as well as terminology. Will no longer like various weblogs. An individual the truth is know very well what you?re communicating roughly too. So much which you helped me wish to explore more. Your own weblog offers grow to be a stepping-stone for me personally, my buddy.

  13. Bobby Debell says:

    very nice post, i definitely love this website, carry on it

  14. Anonymous says:

    You have a lot of talent and a flair for writing. This is quality information and writing. I haven’t found such great content in many months. You have hit on some valid points. Thank you.

  15. peapod says:

    Some truly fantastic posts on this internet site , thankyou for contribution.

  16. TOM says:

    Really informative and superb structure of subject matter, now that’s user pleasant (:.

  17. Berwyn Illinois Crime News says:

    I believe this internet site contains very good indited subject material blog posts.

  18. watch movies says:

    I’m really impressed with your writing abilities and also with the format of Herpes Simplex Encephalitis HSE, Real Estate Savant Justice for Marcus, a Brain Injured Young Man With Aphasia… Is that this a paid subject matter or did you customize it yourself? Anyway keep up the excellent high quality writing, it is uncommon to look at a great blog like this one these days.

  19. Kerstin Mostrom says:

    I like this web blog so much, saved to bookmarks .

  20. iphone says:

    I have been checking out many of your posts and it’s pretty clever stuff. I will surely bookmark your website.

  21. Vickie says:

    Dodgen407, Furniture stores in Oklahoma City,
    Thank your for reading our site.

  22. Vickie says:

    Kipka of
    Tom Shoes Coupon,
    Thank you for reading our website!

  23. Vickie says:

    Pay Monthly Laptops,
    Thank you for your comment. If I can be of any assistance please contact me.

  24. PML says:

    Howdy! This is my first visit to your blog! We are a group of volunteers and starting a new initiative in a community in the same niche. Your blog provided us useful information to work on. You have done a extraordinary job!

  25. Toms Shoes says:

    Appreciate it for this post, I am a big fan of this web site would like to continue updated.

  26. FSTOC says:

    I’m no professional in this subject matter, but I do know what I like to read. This is excellent content with well laid out viewpoints. I will certainly post a link to https://realestatesavant.wordpress.com/herpes-simplex-encephalitis-hse/ on my site.

  27. Dorman 66 says:

    I simply needed to thank you very much once more. I do not know the things that I could possibly have taken care of in the absence of the ideas discussed by you on my subject matter. It absolutely was the scary circumstance for me, but viewing your expert tactic you solved it took me to leap over contentment. Now i am grateful for the service and even hope that you find out what a great job you have been getting into teaching many people with the aid of your blog post. I am certain you have never met all of us.

  28. furniture stores in hawaii says:

    bonjour. i enjoy reading your blog Herpes Simplex Encephalitis HSE | Real Estate Savant …. Justice for Marcus, a Brain Injured Young Man With Aphasia. and will most definitely insert a link to https://realestatesavant.wordpress.com/herpes-simplex-encephalitis-hse/ on my site.

  29. Garmin says:

    Dear admin, thnx for sharing this blog post. I found it wonderful. Most effective regards, Victoria…

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s