Herpes Encephalitis (HSE) as a Serious Disease!
Encephalitis means inflammation of the brain tissue, and herpes simplex encephalitis (HSE) is caused by a virus named herpes simplex or simply herpes virus.
Herpes group of viruses include herpes simplex and several other familiar viruses like chickenpox virus, virus causing infectious mononucleosis etc. Herpes simplex virus is of two types, type 1 & 2; HSE is mostly caused by type 1.
Herpes simplex type 2 by and large causes the genital infection in adults although the neonatal herpes encephalitis too is mostly cause by this virus subtype, and is acquired by the baby during delivery through the herpes infected vagina.
In adults, herpes simplex type 2 may occasionally cause meningitis.
Frequency & distribution
HSE is seen throughout the world. It is considered as a sporadic disease in the sense it is seen randomly rather then in epidemics (several cases occurring in the same place simultaneously) or endemics (cases occurring in the same place for long time).
No age, sex or race is exempt although incidence is more in younger and older people.
What causes Herpes Encephalities / HSE
Herpes group of viruses are notorious to live in a dormant condition for long time in the body after the initial or primary infection, and they do so usually in the nerve ganglions (a cluster of nerve cells or neurons).
It is assumed that such hibernating viruses in a ganglion by name trigeminal ganglion (ganglion on 5th cranial nerve or trigeminal nerve) become reactive for some reason and then travel towards the brain along the axon (nerve fiber) and ultimately reach the brain tissue and infiltrate the neurons.
Another cranial nerve by name olfactory nerve (1st cranial nerve or nerve of smell) may also be implicated with the virus-entry to the brain.
- Confusion/ disorientation
- Decreased level of consciousness
- Seizures (fits) etc.
The investigations generally required include;
- CT (CAT scan) of brain
- MRI of brain
- CSF (cerebrospinal fluid) analysis
- Brain biopsy
MRI of the brain is superior to CT scanning for the diagnosis of herpes encephalitis and these studies show abnormal changes in the frontal and temporal lobes of the brain which are mostly involved. Brain swelling and small amounts of hemorrhage may be seen too.
CSF analysis is of immense value. CSF pressure is elevated, cell count is increased and consists of mostly lympocytes, some red blood cells may be seen too, protein is elevated and glucose is usually normal.
Gram stain, bacterial culture & antigen tests should all come normal. Herpes PCR is a special test which is highly sensitive for this condition.
Although brain biopsy was frequently done in the past, since the advent of herpes PCR it is rarely performed.
A properly done and analyzed brain biopsy is extremely sensitive for the diagnosis of HSE however it caries risk of bleeding & death so now-a-days executed only if no choice is available.
EEG may shows a characteristic finding called PLED (periodic lateralized epileptiform discharges).
- Stabilization of the patient
- Intravenous Acyclovir
- Pain killers
- Medications to control fever
- Anticonvulsant medications (if fits occur)
- Intravenous fluids
Acyclovir is an anti-viral agent and supposed to be used with all confirmed or suspected HSE patients. It is given intravenously three times/day x for about 10 to 14 days. Earlier the acyclovir is started the better out come.
Early treatment with acyclovir has reduced the death rate and complications of this serious disease, however many of the survivors are still left with serious sequel in the form major cognitive deficits, seizures etc.