Updated: Sep 2, 2009
The human herpesvirus (HHV) family includes 2 clinically important strains, also known as herpes simplex virus (HSV). Human herpesvirus 1 (HHV-1), also called herpes simplex virus type 1 (HSV-1), causes oral lesions (so-called fever blisters); these are common and may respond to antiviral medications, although they spontaneously remit in most cases. Human herpesvirus 2 (HHV-2), also known as herpes simplex virus type 2 (HSV-2), causes genital lesions. It was previously thought to appear within 1-2 weeks of primary infection, then to recur with lessening severity. That lesions may appear clinically at any interval after primary infection is now known. HSV-2 may be treated with antiviral medications.
Patients with HSV may require long-term antiviral treatment if they have recurrent lesions or involvement of other organ systems (eg, herpes simplex keratitis). HSV remains dormant in the nervous system; rarely, it presents as encephalitis, possibly by direct transmission through peripheral nerves to the CNS. This encephalitis is a neurologic emergency and the most important neurologic sequela of HSV.
Besides causing local outbreaks, HSV-1 and HSV-2 are associated with encephalitis. HSV-1 is the more common cause of adult encephalitis. HSV-2 is the more common cause of newborn encephalitis, which is associated with maternal genital infections. Pathophysiology of this encephalitis is poorly understood in humans. Animal models suggest that the virus enters the CNS via peripheral nerves. Virus-induced apoptosis may play a role in the molecular pathogenesis of herpes simplex encephalitis (HSE). HSV is an enveloped, double-stranded DNA virus. It is part of the herpes family, which also includes varicella-zoster virus (VZV, or HHV-3) and cytomegalovirus (CMV, or HHV-5).
The encephalitis affects the temporal lobes of the brain in most cases. Wasay et al report temporal lobe involvement in 60% of patients.1 Fifty-five percent of patients demonstrated temporal and extratemporal pathology, and 15% of patients demonstrated extratemporal pathology exclusively.
HSE is the most common nonepidemic encephalitis. Incidence is 2 cases per million population per year. HSE 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.
One third of HSE cases occur in children.
| Acute Disseminated Encephalomyelitis | Generalized EEG Waveform Abnormalities |
| Aphasia | Haemophilus Meningitis |
| Aseptic Meningitis | HIV-1 Associated CNS Complications
(Overview) |
| Benign Childhood Epilepsy | Intracranial Epidural Abscess |
| Benign Neonatal Convulsions | Intracranial Hemorrhage |
| Childhood Migraine Variants | Lennox-Gastaut Syndrome |
| Complex Partial Seizures | Leptomeningeal Carcinomatosis |
| Confusional States and Acute Memory
Disorders | Migraine Headache |
| Dissection Syndromes | Migraine Headache: Pediatric Perspective |
| Early Myoclonic Encephalopathy | Migraine Variants |
| EEG in Common Epilepsy Syndromes | Neurosyphilis |
| EEG in Dementia and Encephalopathy | Paraneoplastic Encephalomyelitis |
| EEG in Status Epilepticus | Seizures and Epilepsy: Overview and
Classification |
| Epileptiform Discharges | Simple Partial Seizures |
| Frontal Lobe Epilepsy | Status Epilepticus |
| Frontal Lobe Syndromes | Temporal Lobe Epilepsy |
Complex partial status epilepticus
Myoclonus
Partial seizures with secondary generalization
Seizure, partial (focal)
Benign epilepsy syndromes
Management of increased intracranial pressure in the neuro ICU
Management of intracranial hemorrhage in the neuro ICU
EEG in coma
Increased intracranial pressure
Neuro-Behçet disease
Orbitofrontal or limbic encephalitis may be seen. One hallmark of the condition is significant hemorrhage in these locations. Cowdry A inclusions are seen.
When HSE diagnosis cannot be established, brain biopsy can yield definitive diagnosis. Biopsy may be considered when lumbar puncture is precluded or nondiagnostic but is rarely used today with the availability of nontoxic and effective antiviral medications.
The goals of therapy are to reduce morbidity and to prevent complications.
Pharmacotherapy for HSE is available in the form of acyclovir and vidarabine.
Patient outcome is improved when treated with either of these agents. Acyclovir is more effective and less toxic.
When the diagnosis of HSE is suspected or has been established, IV acyclovir should be initiated immediately.
A 2009 Cochrane database review pulled data from 17 trials that compared interventions used for the prevention and treatment of herpes simplex virus in patients being treated for cancer. The authors concluded that aciclovir is effective in preventing and treating herpes simplex virus infections. Valaciclovir was not found to be more effective than aciclovir, nor did a higher dose of valaciclovir make a difference. Some evidence indicated that placebo, as a prophylaxis, is more effective than prostaglandin E, but the risk of bias was unclear in all trials.15
The goals of using antivirals are to shorten the clinical course, prevent complications, prevent development of latency and subsequent recurrences, decrease transmission, and eliminate established latency.
Has demonstrated inhibitory activity against both HSV-1 and HSV-2 and is taken up selectively by infected cells; rate of mortality from HSE before use of acyclovir was 60-70%—since acyclovir, it is approximately 30%.
10 mg/kg/dose IV or 500 mg/m2/dose IV q8h
Administer as in adults
Half-life prolonged and toxicity increased by concomitant probenecid or zidovudine
Documented hypersensitivity
B - Fetal risk not confirmed in studies in humans but has been shown in some studies in animals
Use caution in patients with renal failure or receiving other nephrotoxic drugs concurrently
These agents are used to terminate clinical and electrical seizure activity as rapidly as possible and prevent seizure recurrence.
Effective in treatment of complex partial seizures; appears to act by reducing polysynaptic responses and blocking posttetanic potentiation.
Once a response is attained, attempt to reduce dose to minimum effective level or to discontinue drug at least once q3mo.
200 mg PO bid or 100 mg suspension PO qid; increase at weekly intervals by no more than 200 mg/d tid/qid (bid with extended release) until best response obtained; not to exceed 1600 mg/d
<6 years: 10-20 mg/kg/d PO bid/tid (qid with suspension); increase weekly to achieve optimal clinical response administered tid/qid
6-12 years: 100 mg PO bid or 50 mg suspension PO qid; increase at weekly intervals by gradually adding another 100 mg/d on tid/qid schedule (bid with extended release) until best response obtained; not to exceed 1000 mg/d
>12 years: Administer as in adults; not to exceed 1000 mg/d in children aged 12-15 y or 1200 mg/d in patients >15 y
May decrease primidone and phenobarbital levels; serum concentrations may be increased by concurrent primidone or phenobarbital; plasma levels and toxicity may increase with concurrent cimetidine—interaction of greatest clinical importance when cimetidine added to carbamazepine during first 4 wk of therapy; levels increase 38-123% within 30 d of danazol administration
Documented hypersensitivity, history of bone marrow depression, concomitant MAOIs, concomitant danazol
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Do not use concomitantly with MAOIs; discontinue MAOIs for >14 d before carbamazepine administration
This drug is not a simple analgesic; do not use for relief of minor aches or pains; use caution in patients with increased intraocular pressure
Obtain complete pretreatment blood counts, including platelets and possibly reticulocytes and serum iron, as baseline; monthly CBC, differential, platelets during the first 2 mo and thereafter yearly or every other year
May produce drowsiness, dizziness, or blurred vision; patients should observe caution while driving or performing other tasks requiring alertness, coordination, or physical dexterity
A hydantoin, its primary site of action appears to be motor cortex, where it may inhibit spread of seizure activity; may reduce maximal activity of brain stem centers responsible for tonic phase of grand mal seizures.
Dose should be individualized; if daily dosage cannot be divided equally, larger dose should be given before bedtime.
Phosphorylated formulation, fosphenytoin, available for parenteral use (IV/IM).
Initial: 100 mg PO/IV tid or 125 mg suspension PO tid
Maintenance: 300-400 mg/d PO/IV divided tid (qd/bid if extended release); increase to 600 mg/d (625 mg/d suspension) prn; not to exceed 1500 mg/d
Initial: 5 mg/kg/d PO/IV divided bid/tid
Maintenance: 4-8 mg/kg PO/IV divided bid/tid; not to exceed 300 mg/d
> 6 years: May require minimum adult dose (300 mg/d); not to exceed this dose
Toxicity may be increased by amiodarone, benzodiazepines, chloramphenicol, cimetidine, disulfiram, ethanol (acute ingestion), fluconazole, isoniazid, metronidazole, miconazole, omeprazole, phenacemide, phenylbutazone, succinimides, sulfonamides, trimethoprim, and valproic acid; effects may be decreased by barbiturates, carbamazepine, diazoxide, ethanol (chronic ingestion), rifampin, theophylline, antacids, charcoal, and sucralfate; may decrease effects of acetaminophen, amiodarone, carbamazepine, cardiac glycosides, corticosteroids, dicumarol, disopyramide, doxycycline, estrogens, haloperidol, methadone, metyrapone, mexiletine, oral contraceptives, quinidine, theophylline, and valproic acid
Documented hypersensitivity; SA block, sinus bradycardia, second- and third-degree AV block, Adams-Stokes syndrome (because of effects on ventricular automaticity)
D - Fetal risk shown in humans; use only if benefits outweigh risk to fetus
Death from cardiac arrest has occurred after too-rapid IV administration, sometimes preceded by marked QRS widening; discontinue if hepatic dysfunction occurs; discontinue if skin rash appears—do not resume if rash is exfoliative, bullous, or purpuric; use caution in patients with diabetes (may raise blood glucose) or acute intermittent porphyria
May cause blood dyscrasias; obtain baseline CBC and urinalysis, repeat monthly for several months thereafter
If chronic suppressive therapy is needed, acyclovir or famciclovir can be used orally.
For excellent patient education resources, visit eMedicine's Teeth and Mouth Center and Brain and Nervous System Center. Also, see eMedicine's patient education articles Oral Herpes, Cold Sores, and Encephalitis.
Wasay M, Mekan SF, Khelaeni B, et al. Extra temporal involvement in herpes simplex encephalitis. Eur J Neurol. Jun 2005;12(6):475-9. [Medline].
Whitley RJ, Soong SJ, Dolin R, et al. Adenine arabinoside therapy of biopsy-proved herpes simplex encephalitis. National Institute of Allergy and Infectious Diseases collaborative antiviral study. N Engl J Med. Aug 11 1977;297(6):289-94. [Medline].
Elbers JM, Bitnun A, Richardson SE. A 12-year prospective study of childhood herpes simplex encephalitis: is there a broader spectrum of disease?. Pediatrics. Feb 2007;119(2):e399-407. [Medline].
Shelley BP, Raniga SB, Al-Khabouri J. An unusual late complication of intracerebral haematoma in herpes encephalitis after successful acyclovir treatment. J Neurol Sci. Jan 31 2007;252(2):177-80. [Medline].
Marschitz I, Rodl S, Gruber-Sedlmayr U. Severe chorea with positive anti-basal ganglia antibodies after herpesencephalitis. J Neurol Neurosurg Psychiatry. Jan 2007;78(1):105-7. [Medline].
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McGrath NM, Anderson NE, Hope JK, et al. Anterior opercular syndrome, caused by herpes simplex encephalitis. Neurology. Aug 1997;49(2):494-7. [Medline].
Mondal G, Kumar R, Ghosh JK, Basu K, Chatterjee S. Basal ganglia involvement in a child with herpes simplex encephalitis. Indian J Pediatr. May 27 2009;[Medline].
Li JZ, Sax PE. HSV-1 encephalitis complicated by cerebral hemorrhage in an HIV-positive person. AIDS Read. Apr 2009;19(4):153-5. [Medline].
Mitchell BM, Stevens JG. Neuroinvasive properties of herpes simplex virus type 1 glycoprotein variants are controlled by the immune response. J Immunol. Jan 1 1996;156(1):246-55. [Medline].
Geiger KD, Nash TC, Sawyer S, et al. Interferon-gamma protects against herpes simplex virus type 1-mediated neuronal death. Virology. Nov 24 1997;238(2):189-97. [Medline].
Cathomas R, Pelosi E, Smart J. Herpes simplex encephalitis as a complication of adjuvant chemotherapy treatment for breast cancer. Clin Oncol (R Coll Radiol). Jun 2005;17(4):292-3. [Medline].
Schloss L, Falk KI, Skoog E, Brytting M, Linde A, Aurelius E. Monitoring of herpes simplex virus DNA types 1 and 2 viral load in cerebrospinal fluid by real-time PCR in patients with herpes simplex encephalitis. J Med Virol. Jun 23 2009;81(8):1432-1437. [Medline].
Beneto A, Gomez E, Rubio P, et al. [Periodical EEG pattern modifications in herpetic encephalitis treated with acyclovir]. Rev Neurol. Jul 1996;24(131):829-32. [Medline].
[Best Evidence] Glenny AM, Fernandez Mauleffinch LM, Pavitt S, Walsh T. Interventions for the prevention and treatment of herpes simplex virus in patients being treated for cancer. Cochrane Database Syst Rev. Jan 21 2009;CD006706. [Medline].
Utley TF, Ogden JA, Gibb A, et al. The long-term neuropsychological outcome of herpes simplex encephalitis in a series of unselected survivors. Neuropsychiatry Neuropsychol Behav Neurol. Jul 1997;10(3):180-9. [Medline].
Athmanathan S, Vydehi BV. Neuronal apoptosis in herpes simplex virus-1 encephalitis (HSE). Medical Microbiology. 2001;19:127-131.
Baxter P, Forsyth R, Eyre J. Relapse and movement disorder after herpes simplex encephalitis. J Child Neurol. Jun 1997;12(4):283. [Medline].
Brown ZA, Vontver LA, Benedetti J, et al. Effects on infants of a first episode of genital herpes during pregnancy. N Engl J Med. Nov 12 1987;317(20):1246-51. [Medline].
Cinque P, Cleator GM, Weber T, et al. The role of laboratory investigation in the diagnosis and management of patients with suspected herpes simplex encephalitis: a consensus report. The EU Concerted Action on Virus Meningitis and Encephalitis. J Neurol Neurosurg Psychiatry. Oct 1996;61(4):339-45. [Medline].
Hasegawa T, Kanno S, Kato M, et al. Neuro-Behçet's disease presenting initially as mesiotemporal lesions mimicking herpes simplex encephalitis. Eur J Neurol. Aug 2005;12(8):661-2. [Medline].
Jereb M, Lainscak M, Marin J, Popovic M. Herpes simplex virus infection limited to the brainstem. Wien Klin Wochenschr. Jul 2005;117(13-14):495-9. [Medline].
Preiser W, Weber B, Klos G, et al. Unusual course of herpes simplex virus encephalitis after acyclovir therapy. Infection. Sep-Oct 1996;24(5):384-9. [Medline].
Shian WJ, Chi CS. Magnetic resonance imaging of herpes simplex encephalitis. Zhonghua Min Guo Xiao Er Ke Yi Xue Hui Za Zhi. Jan-Feb 1996;37(1):22-6. [Medline].
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Whitley RJ, Soong SJ, Linneman C Jr, et al. Herpes simplex encephalitis. Clinical Assessment. JAMA. Jan 15 1982;247(3):317-20. [Medline].
herpes, genital herpes, herpes encephalitis, encephalitis, HSE, HSV-1, HSV-2, cold sores, fever blisters, herpes simplex virus, human herpesvirus, HHV, HHV-1, herpes simplex virus type 1, herpes simplex virus type 2, herpes simplex encephalitis
Wayne E Anderson, DO, Assistant Professor of Internal Medicine/Neurology, Western University of Health Sciences; Assistant Professor of Family Medicine, Touro University College of Osteopathic Medicine; Consulting Staff in Pain Management, Department of Neurology, California Pacific Medical Center
Wayne E Anderson, DO is a member of the following medical societies: American Academy of Neurology, American Medical Association, American Society of Law Medicine and Ethics, California Medical Association, and San Francisco Medical Society
Disclosure: Cephalon Honoraria Speaking and teaching; Pfizer Honoraria Speaking and teaching; King Honoraria Consulting
Ramon Diaz-Arrastia, MD, PhD, Assistant Professor, Department of Neurology, Comprehensive Epilepsy Center, University of Texas Southwestern
Ramon Diaz-Arrastia, MD, PhD is a member of the following medical societies: Alpha Omega Alpha, American Academy of Neurology, New York Academy of Sciences, and Phi Beta Kappa
Disclosure: Nothing to disclose.
Francisco Talavera, PharmD, PhD, Senior Pharmacy Editor, eMedicine
Disclosure: eMedicine Salary Employment
Selim R Benbadis, MD, Professor, Director of Comprehensive Epilepsy Program, Departments of Neurology and Neurosurgery, University of South Florida School of Medicine, Tampa General Hospital
Selim R Benbadis, MD is a member of the following medical societies: American Academy of Neurology, American Academy of Sleep Medicine, American Clinical Neurophysiology Society, American Epilepsy Society, and American Medical Association
Disclosure: Nothing to disclose.
Matthew J Baker, MD, Consulting Staff, Collier Neurologic Specialists, Naples Community Hospital
Matthew J Baker, MD is a member of the following medical societies: American Academy of Neurology
Disclosure: Nothing to disclose.
Nicholas Y Lorenzo, MD, Chief Editor, eMedicine Neurology; Consulting Staff, Neurology Specialists and Consultants
Nicholas Y Lorenzo, MD is a member of the following medical societies: Alpha Omega Alpha and American Academy of Neurology
Disclosure: Nothing to disclose.
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