Herpes simplex encephalitis (HSE) is an infectious inflammation of the brain, caused, in adults and adolescents, by the herpes simplex virus type I. It leads to a multitude of neurological symptoms, that can either be generalized or focal.

The symptoms most typically related to HSE include fever, which is present in up to 90% of the patients and cephalalgia [1]. The full course of the clinical symptomatology tends to develop over a period of some days. Convulsions and psychiatric sequelae, such as psychotic incidences and behavioral pattern modifications are also common [1]. Patients may progress to a lethargy, confusion, and delirium. Profound neurological symptomatology also encompasses memory loss, speech impairment or aphasia, anosmia, limb weakness or even hemiparesis. Retinitis may also occur as a result of HSE and meningismus may be observed. The clinical picture in herpes simplex encephalitis infection is extremely broad and there is no pathognomonic clinical finding that can aid towards a precise diagnosis of the disorder [2]. Immunocompromised individuals tend to present with a less typical or less profound set of symptoms as compared to the immunocompetent population [3].

Neonatal herpes simplex encephalitis is usually a result of a herpes simplex type II infection and initial symptoms develop during the first two weeks after birth. The clinical picture includes seizures, loss of appetite, weakness, and lethargy, along with irritability and tremors. Lesions on the skin may also be observed.

• Fever

  Classic triad of fever, nuchal rigidity, and altered mental status Photophobia, phonophobia, rash associated with meningococcemia, concomitant sinusitis or otitis, swelling of the fontanelle in infants (0-6 months) Brain abscess Fever, headache, hemiparesis [wikidoc.org]

  The clinical picture is often one of spontaneous and rapid developments of fever, headache, confusion, and seizures. Fever and abnormal mental status are the primary signs and symptoms of HSVE, occurring in >90% of patients. [hindawi.com]

  A 30-year-old man was admitted in PGIMER with the complaints of fever, altered sensorium and seizures. [ncbi.nlm.nih.gov]

  In pregnancy HSE manifests very much the same way as in the general population with the triad of headache, fever and seizures. [encephalitis.info]

  If you have viral meningitis, symptoms may include fever, light sensitivity, headache, and a stiff neck. [hopkinsmedicine.org]

• Pain

  Orolabial herpes (Figure 1): edema and pain may lead to dysphagia. Genital herpes can be associated with extreme pain, edema, and dysuria. [infectiousdiseaseadvisor.com]

  Patients may develop painful, severe visual impairment over a few days, or experience an insidious onset with mild visual symptoms such as floaters. [mja.com.au]

  By day three he was feeling much better, although complained of jaw pain, and it was noted that his jaw was not closing properly. His co-ordination was also still mildly impaired with bilateral arm drift on examination. [priory.com]

  Anti-viral or anti-bacterial medicines may be prescribed, along with other medications to relieve the symptoms, such as corticosteroids to reduce inflammation, anti-convulsants, and medications for pain relief. [brainfoundation.org.au]

  Severe health consequences Untreated and undiagnosed HSV can lead to varying and severe health consequences, including painful chronic infection, miscarriage or premature birth, and fatal infection in newborns. [diagnostics.roche.com]

• Malaise

  Adult: usually HSV-1 Transmission: see herpes simplex virus infections Infectivity: highly contagious References:[2] Pathophysiology Clinical features Prodromal phase Duration: few hours to days Nonspecific symptoms Fever Headache Nausea and vomiting Malaise [amboss.com]

  […] children (33% <20y) and the elderly (50% >50y) the classic triad of fever, headache and altered CAUSE HSV-1 encephalitis is more common in adults HSV-2 infection is more common in neonates CLINICAL FEATURES Classic presentation flu-like illness with malaise [litfl.com]

  […] common, and most severe, in children (33% 50y) the classic triad of fever, headache and altered CAUSE HSV-1 encephalitis is more common in adults HSV-2 infection is more common in neonates CLINICAL FEATURES Classic presentation flu-like illness with malaise [lifeinthefastlane.com]

  Infected patients develop prodromal symptoms, such as malaise, fever, headache, and nausea, followed by the acute or subacute onset of neurological symptoms, which can include lethargy, confusion, and delirium. [hindawi.com]

• Anosmia

  Profound neurological symptomatology also encompasses memory loss, speech impairment or aphasia, anosmia, limb weakness or even hemiparesis. Retinitis may also occur as a result of HSE and meningismus may be observed. [symptoma.com]

  Short term memory impairment (70%), anosmia (65%), and dysphasia (41%) were the most common signs. [jnnp.bmj.com]

  After the initial symptoms appear, affected individuals may develop speech abnormalities such as a diminished ability to communicate by speech, writing, and/or signs (aphasia), absence of the sense of smell (anosmia), and memory loss. [rarediseases.org]

• Vomiting

  Abstract A 15-year-old girl was referred to our hospital due to fever, headache, and vomiting of 7 days duration and focal motor convulsion at the day of referral. [ncbi.nlm.nih.gov]

  Signs and symptoms include fever, headaches, vomiting, seizures and psychiatric manifestations. Definition (MSH) An acute (or rarely chronic) inflammatory process of the brain caused by SIMPLEXVIRUS infections which may be fatal. [fpnotebook.com]

  A 2.5-year-old boy was brought to our emergency department with a 24-h history of fever, vomiting, dysphagia, and brief episodes of teeth-clenching. He was febrile (38.2°C), dysarthric, and drooling, with otherwise normal examination results. [jcm.asm.org]

• Nausea

  The manifestations of HSVE include low-grade pyrexia accompanied by severe headache, nausea, vomiting, and lethargy, followed by neurological features, which may include cognitive dysfunction (confusion, acute memory disturbances and disorientation), [orpha.net]

• Loss of Appetite

  The clinical picture includes seizures, loss of appetite, weakness, and lethargy, along with irritability and tremors. Lesions on the skin may also be observed. [symptoma.com]

  She described a loss of appetite for 6 weeks but had no headache, fever, rash, pleuritic chest pain or shortness of breath suggestive of a lupus flare. Her initial visual acuity was 6/9 in her right eye and “hand movements” in her left eye. [mja.com.au]

  The patient had been previously well, although one week prior he had had flu-like symptoms, including loss of appetite and general myalgia, as well as a swelling on the right side of his neck which had resolved on its own. [casesjournal.biomedcentral.com]

  Patients with primary infection may have a prodrome, which can include symptoms, such as fever, malaise, loss of appetite, and localized pain and/or burning at the site the lesions will occur. [infectiousdiseaseadvisor.com]

• Blurred Vision

  One week following the last fraction of radiotherapy, he presented again with a 5-day history of progressive fatigue, intermittent fevers of up to 101°F, confusion, blurred vision and sharp right-sided headache. [karger.com]

• Diplopia

  Patient A 37-year-old woman was admitted to the hospital with fever, diplopia, left hemiparesis, sensory change in the face and limbs, personality changes, frontal dysexecutive syndrome, and a stiff neck. [jamanetwork.com]

• Skin Lesion

  Figure 1: Herpes skin lesion. [e-ijd.org]

  Skin lesions usually are not found in association with herpes simplex encephalitis. Herpes simplex encephalitis is caused by a virus known as herpes simplex virus (HSV). [rarediseases.org]

• Visual Hallucination

  Although rare, visual impairment can be associated with complex visual hallucinations indicative of Charles Bonnet syndrome. [ncbi.nlm.nih.gov]

  Motor agitation, disorientation, drowsiness, visual hallucinations, and aggressiveness were the most frequent symptoms. Other authors, such as Boyapati et al.13 also described such neuropsychological symptoms as psychosis and delirium. [elsevier.es]

  Delusions of misidentification of staff were present, as were visual hallucinations. [hindawi.com]

  The patient started experiencing a subjective slowing of mentation, visual hallucinations as well as auditory hallucinations. [jmedicalcasereports.com]

• Delusion

  Delusions of misidentification of staff were present, as were visual hallucinations. [hindawi.com]

  On October 14, he became suspicious, had delusion of persecution, and ran around. [dovepress.com]

  […] symptoms: memory impairment (n=31); speech disorders (n=18); cognitive impairment (n=15); disorientation (n=11); focal neurological signs (n=8); dysexecutive syndrome (n=3); disinhibition (n=2); perseveration (n=2); and hallucinations or aggressiveness or delusion [cambridge.org]

• Auditory Hallucination

  The patient started experiencing a subjective slowing of mentation, visual hallucinations as well as auditory hallucinations. [jmedicalcasereports.com]

• Gustatory Hallucination

  In addition, because of the involvement of the frontal and temporal lobes, patients often display bizarre behaviour, personality changes, anosmia, and gustatory hallucinations. [neuropathology-web.org]

• Seizure

  Clinical improvement was clear with prompt recovery and acute control of seizures. The only remaining deficits were mild memory and attention impairments. Seizures did not recur in the next 6 months. [ncbi.nlm.nih.gov]

  In terms of risk to the unborn baby, seizures in the mother can pose a serious risk and therefore seizure control is of utmost important. [encephalitis.info]

• Headache

  […] other causes of headache, altered mental status and seizures such as brain tumors and delirium trmemns. [wikidoc.org]

  On hospital day 3, she had a sudden onset of vomiting and severe headache. Brain CT showed frank temporal lobe hemorrhage. Despite aggressive medical treatment, she became increasingly drowsy. [ncbi.nlm.nih.gov]

  If you have viral meningitis, symptoms may include fever, light sensitivity, headache, and a stiff neck. [hopkinsmedicine.org]

  Case Report: A 27-year-old woman with no past medical history presented with altered mental state, headaches, and seizures. She had a nasal dermal filler injection for aesthetic purpose five weeks before her acute presentation. [ukm.pure.elsevier.com]

• Meningism

  PMID 22421697. ↑ 20.0 20.1 Meningitis and Encephalitis Fact Sheet. National Institute of Neurological Disorders and Stroke. [wikidoc.org]

  The meninges are the layers of thin tissue that cover your brain. If these tissues become infected, it’s called meningitis. When your brain becomes inflamed or infected, the problem is called encephalitis. [hopkinsmedicine.org]

  The coronal post-gadolinium T1-weighted image on the right shows abnormal meningeal thickening and enhancement, arrowheads. [svuhradiology.ie]

  Mollaret's meningitis Other names Benign recurrent lymphocytic meningitis Meninges of the central nervous system: dura mater, arachnoid, and pia mater. [en.wikipedia.org]

• Confusion

  Most frequent symptoms at admission were fever, confusion, aphasia and seizures. Mortality rate was 11 %. 2 patients presented a clinical relapse. In conclusion, the most frequent neurological sequelae were aphasia and amnesia. [ncbi.nlm.nih.gov]

  Although it can present discreetly with confusion, altered behaviour and sleepiness. [encephalitis.info]

  These symptoms may include a stiff neck, altered reflexes, confusion, convulsions, and paralysis. [rarediseases.org]

• Cognitive Impairment

  Despite profound cognitive impairment at their clinical nadir, both patients recovered fully. [ncbi.nlm.nih.gov]

  The most important modifiable risk factors for cognitive impairment are alcohol excess, smoking, limited exercise, and not keeping an active mind for learning. [encephalitis.info]

The diagnosis of herpes simplex encephalitis requires a plethora of tests for confirmation. These include a medical history that is expected to be compatible with the main symptoms of the infection, a lumbar puncture to drain cerebrospinal fluid (CSF) for analysis, a CSF polymerase-chain-reaction test (PCR), a brain magnetic resonance imaging scan (MRI) and, possibly, a computed tomography scan (CT) of the brain or brain biopsy [4] [5].

CSF cytology

Cerebrospinal fluid analysis in a case of HSE is expected to display red blood cells and xanthochromia. Pleocytosis, with white blood cell levels of mononuclear type approximately at 10-500 per mL and augmented protein levels at 60-700 mg/dL are also exhibited in a typical analysis. Glucose may be slightly diminished. During the initial phase of the infection, CSF analysis may be normal in a considerable number of patients (app 10-15%) [6]. A viral HSV-II culture is solely possible in neonates.

Imaging modalities

Neuroimaging is widely used to detect brain inflammation in patients with a suspected HSE and, additionally, to differentiate between this disorder and other conditions that could result in the same symptomatology, such as a tumor. MRI scans are substantially preferred to CT scans with reference to the HSE diagnosis since the sensitivity of an MRI scan is superior [7].

PCR

A PCR test, carried out on the CSF sample, can directly detect viral load and greatly accelerate the diagnosis of HSE, both in adults and neonates. With the advent of PCR, the use of brain biopsy has diminished, since PCR constitutes a non-invasive, accurate tool for the detection of herpes simplex encephalitis, whose specificity and sensitivity amount to 98-100% and 94-98% respectively [8] [9].

• Cerebrospinal Fluid Abnormality

  A presumptive diagnosis of herpes simplex encephalitis was made in five patients with distinctive clinical findings and compatible cerebrospinal fluid abnormalities. [jamanetwork.com]

  fluid",[2] cerebrospinal fluid abnormalities may not be detectable for the entire time.[6] Diagnosis can be elusive, as Helbok et al. note: "in reality, many more weeks, even months pass by until the diagnosis is established. [en.wikipedia.org]

• Periodic Lateralized Epileptiform Discharges

  Watemberg and Morton (March 7 issue) describe a case of herpes simplex encephalitis in a 13-year-old boy and present the classic electroencephalographic finding of periodic lateralized epileptiform discharges. 1 Whereas it is gratifying to learn that [nejm.org]

  Electroencephalogram revealed periodic lateralized epileptiform discharges (PLEDS) in the left fronto-temporal lobes. [academic.oup.com]

  In addition, the patient had periodic lateralized epileptiform discharges on electroencephalogram, which supports the diagnosis of herpes encephalitis. [emedicine.medscape.com]

  Typical findings include diffuse slowing, focal temporal changes, periodic complexes, and periodic lateralizing epileptiform discharges (PLEDS). These latter findings are highly suggestive of HSE, in the proper clinical context. [casemed.case.edu]

• Hyponatremia

  Introduction This report describes a patient with herpes simplex encephalitis who exhibited, during the acute stage of his illness, severe, transient hyponatremia with renal sodium loss presumably induced by inappropriate and excessive production of antidiuretic [jamanetwork.com]

  Disorientation, hyponatremia and abnormalities in initial brain CT were identified as new prognostic factors. [ncbi.nlm.nih.gov]

  Laboratory values were only significant for hyponatremia with urine hyperosmolality consistent with syndrome of inappropriate antidiuretic hormone secretion. [karger.com]

  Other Names Learn More: HPO ID 80%-99% of people have these symptoms CSF lymphocytic pleiocytosis 0200149 EEG abnormality 0002353 30%-79% of people have these symptoms Fatigue Tired Tiredness [ more ] 0012378 Fever 0001945 Headache Headaches 0002315 Hyponatremia [rarediseases.info.nih.gov]

• Klüver-Bucy Syndrome

  We treated a patient with relapsing HSE of the contralateral temporal lobe, resulting in Klüver-Bucy syndrome, after a full-dose acyclovir treatment. [ncbi.nlm.nih.gov]

  Long term sequelae of HSE include neuropsychiatric and cognitive defects, including anterograde amnesia, dysnomia, Klüver-Bucy syndrome and epilepsy [ 8 ]. [raredisorders.imedpub.com]

  Kluver-Bucy syndrome, hypersexuality, and the law. Neurocase 2010;16:140-5. 12. Stewart JT. Carbamazepine treatment of a patient with Klüver-Bucy syndrome. J Clin Psychiatry 1985;46:496-7. 13. Jha S, Patel R. [cjhr.org]

  An autopsy case of probable herpes simplex encephalitis (HSE) showed the partial Klüver-Bucy syndrome from 1 to 7 months after the onset, which consists of strong oral tendencies, emotional changes and possible hypersexuality. [dict.cnki.net]

• Diffuse Encephalopathy

  Nonetheless, the clinical picture and ancillary diagnostic studies are compatible with a bilateral diffuse encephalopathy involving predominantly hippocampal and adjacent mesial temporal regions.Because of the predilection of herpes simplex encephalitis [jamanetwork.com]

In these cases, it is often appropriate to restart treatment promptly. [encephalitis.info]

[…] and prognosis Treatment is with intravenous antivirals (e.g. acyclovir), and if appropriate, antiepileptics and agents to reduce intracranial pressure. [radiopaedia.org]

Relapsing herpes simplex encephalitis (HSE) rarely occurs after acyclovir treatment. We treated a patient with relapsing HSE of the contralateral temporal lobe, resulting in Klüver-Bucy syndrome, after a full-dose acyclovir treatment. [ncbi.nlm.nih.gov]

Favorable prognosis was observed in 73% of patients. [ncbi.nlm.nih.gov]

RESULTS: Of 251 cases of TL encephalitis, 43% had an infectious etiology compared with 16% with a noninfectious etiology. [ncbi.nlm.nih.gov]

Definition / general Herpes simplex (HSV) encephalitis is a severe necrotizing viral infection preferentially involving the medial temporal and frontal lobes of the brain Epidemiology Most commonly identified etiology of nonepidemic viral encephalitis [pathologyoutlines.com]

Therefore, HSE was not suspected to have a genetic etiology. [anr.fr]

Epidemiology References:[1] Epidemiological data refers to the US, unless otherwise specified. [amboss.com]

METHODS: Epidemiological study: we used the hospital medical and administrative discharge database to identify hospital stays, deaths and ICU admissions relating to HSE in 39 hospitals, from 2010 to 2013. [ncbi.nlm.nih.gov]

Viral aetiology and clinico-epidemiological features of acute encephalitis syndrome in eastern India. Epidemiology and Infection 2014; 142: 2514–2512. 12. Ghannad, MS, et al. Herpes simplex virus encephalitis in Hamadan, Iran. [cambridge.org]

PMSI is becoming a useful and powerful epidemiologic tool [21–23]. [ccforum.biomedcentral.com]

In this article, the author reviews the clinical features, pathogenesis, epidemiology, diagnosis, and management of herpes simplex encephalitis. [medlink.com]

The postoperative viral pathophysiology remains a subject of debate. The rate of adverse outcome is high and early antiviral treatment seems to be a strong predictor of clinical outcome. [ncbi.nlm.nih.gov]

However its pathophysiology remains largely unknown and its poor prognosis is in contrast with the usually good tolerance of most clinical herpetic manifestations. [eurekaselect.com]

Etiology Pathogen: herpes simplex virus Neonates: both HSV-1 and HSV-2 Adult: usually HSV-1 Transmission: see herpes simplex virus infections Infectivity: highly contagious References:[2] Pathophysiology Clinical features Prodromal phase Duration: few [amboss.com]

Can herpes meningoencephalitis be prevented? Avoiding herpes virus infections in the first place can help you prevent herpes meningoencephalitis. [hopkinsmedicine.org]

Ideally the patient should be prescribed on the lowest effective dose of anti-epileptic drugs to prevent seizures. [encephalitis.info]

Decompressive craniectomy prevented imminent brain herniation and a fatal outcome in both of these patients. [ncbi.nlm.nih.gov]

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9. Schloss L, Falk KI, Skoog E, et al. 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. 2009 Aug; 81(8):1432-7