Herpes simplex encephalitis is a diffuse or focal lesion of the medulla caused by herpesviruses HSV-1, HSV-2, Varicella Zoster. The main symptoms of the disease: febrile fever, progressive depression of consciousness, convulsive seizures. At the end of the acute period of infection, residual neurological disorders persist for a long time. To establish a diagnosis, it is necessary to conduct PCR diagnostics of the cerebrospinal fluid, brain tomography, electroencephalogram. Treatment of pathology includes antiviral drugs, decongestant, neurometabolic and anticonvulsant therapy.
G05.1 Encephalitis, myelitis and encephalomyelitis in viral diseases classified elsewhere
Encephalitis of herpetic origin accounts for up to 15-20% of all viral inflammatory processes in brain tissue. Symptoms occur with a frequency of 4-5 cases per 1 million population, and up to a third of patients are children, and about 20% more are in the age category over 60 years. The disease does not lose its relevance in modern neurology, because for a successful outcome of pathology, it is necessary to make a diagnosis and start treatment in time, and delay in providing medical care is fraught with the death of the patient.
The disease in 95% of cases is caused by the herpes simplex virus type 1, which is explained by the high prevalence of the pathogen. According to WHO, about 2/3 of the world’s population under the age of 50 are infected with HSV-1. In second place in frequency is Varicella Zoster Virus (VZV) — the causative agent of chickenpox, herpes zoster. Encephalitis caused by HSV-2 is rare, mainly in immunocompromised patients.
The leading risk factor is a reduced immune status. Herpetic infection proceeds latently, is activated against the background of a violation of the general resistance of the body (with hypothermia, stress, menstruation in women). At risk are people with congenital and acquired immunodeficiency, patients receiving treatment with immunosuppressive drugs. Triggers include reinfection with other strains of herpesviruses, accompanied by autoimmune reactions.
The primary infection of HSV-1, as a rule, occurs in childhood when viral particles enter the mucous membranes, after which the pathogen begins to multiply, migrates to the nerve ganglia, where it remains in a state of latent infection for a long time. Infection with HSV-2 is observed after the beginning of sexual life through the mucous membranes of the genital tract, and the further path of development of the pathogen is similar to HSV-1.
Symptoms of the disease in most cases occur when the infection is reactivated under the influence of provoking factors. Herpesviruses enter the brain hematogenically or through nerve trunks (through the trigeminal or olfactory nerve). From the Gasser node, they spread to the thalamus, subcortical nuclei, and the cortex of the large hemispheres. When spreading along the olfactory tract, the limbic system (hippocampus, temporal cortex) suffers first.
In the typical course of acute cerebral inflammation, several successive stages are distinguished: early, the period of the height of the disease, regression of signs, the stage of residual phenomena. In 70%, the pathology manifests with a sudden high fever (more than 39 ° C), accompanied by intense headaches in the frontotemporal zone, severe drowsiness, vomiting, unrelated to food intake.
On the second or third day, the symptoms are supplemented by disturbances of consciousness: patients begin to get confused in time and space, do not recognize relatives, experience various hallucinations. As the severity of the condition worsens, focal or generalized seizures appear. Occasionally, opercular automatism is observed — repeated smacking or sucking movements.
On average, after 3 days, the disease enters the peak stage. The main manifestation is a deep depression of consciousness up to coma. Patients do not respond to sound and tactile stimuli, but motor reactions to pain stimuli remain within normal limits. Symptoms of decortication or decerebration, arrhythmic breathing, bilateral motor disorders may also occur.
If the patient has been provided with comprehensive treatment, the reverse development of symptoms of herpes simplex encephalitis begins from 3-4 weeks. This stage lasts from several months to 1 year, is characterized by the gradual restoration of temporarily lost neurological functions. At the end of the third stage, about 80% of patients have persistent residual phenomena that can persist for life.
In the acute period, the progression of cerebral edema is unfavorable, which is fraught with its insertion. In the temporo-tentorial form of wedging, a triad of signs occurs: loss of consciousness, hemiparesis, anisocoria. Symptoms of the transtentorial form are the lack of reaction of the pupils to light, fixation of the eyeballs along the median line, bilateral muscle hypertonicity. The work of the respiratory center is often disrupted.
Pathology has a severe course, in the absence of timely medical care, the mortality rate reaches 70%. Even if etiotropic treatment is carried out, a fatal outcome is recorded in 15-20% of patients, more often in infants, the elderly, and patients at risk. In recovered patients, complete regression of neurological symptoms is observed only in 20% of cases, and the rest face residual symptoms.
The most dangerous chronic complication of the disease is considered to be a progressive vegetative state (akinetic mutism), characterized by irreversible destruction of higher mental functions. Patients have preserved consciousness, vital functions (breathing, blood circulation), but there is no cognitive activity. Such patients do not speak, do not react to external stimuli, and require constant care.
Typical consequences of the herpetic form of encephalitis include the Kluver-Bucy syndrome, in which severe long-term mental and cognitive disorders develop. Symptoms of the disorder include an agitated state, aggressiveness, pathological hypersexuality. There are also intellectual disabilities, problems with concentration, memory loss.
The patient is examined by infectious diseases specialists, neurologists, emergency and intensive care doctors. It is possible to suspect encephalitis by the acute onset, the presence of febrile fever, a combination of cerebral and focal symptoms. To confirm the disease, to clarify the etiology of the inflammatory process, the following research methods are prescribed:
- Neuroimaging. The “gold standard” of diagnosis is MRI of the brain, the sensitivity of which when detecting lesions reaches 100% at an early stage of the disease. If this method is unavailable or at later stages of herpes simplex encephalitis, a CT scan of the brain is used.
- Electroencephalography. In the acute period, the EEG shows focal or diffuse disturbances of bioelectric brain activity: high-amplitude delta and theta waves, the appearance of “acute-slow wave” complexes.
- Lumbar puncture. The cerebrospinal fluid has normal transparency, microscopic examination reveals lymphocytic pleiocytosis (about 100 cells in 1 ml), an increase in the amount of protein, a decrease in glucose levels.
- DNA diagnostics. The sensitivity of the PCR study of the cerebrospinal fluid to herpesviruses is 96-98%, and the specificity reaches 94%. Since false negative results are not excluded in the early period of infection, testing is necessarily repeated on the 4th day of the disease.
Herpes simplex encephalitis is characterized by a rapid increase in neurological deficit, progression of general cerebral symptoms, therefore, complex treatment should begin as early as possible. The best chances of full recovery are in patients who started receiving etiotropic drugs on the first day of the manifestation of the disease. Treatment of the disease includes the following groups of medications:
- Antiviral agents. The drug of choice is acyclovir, administered intravenously by drip if herpes simplex encephalitis is suspected even before laboratory confirmation of the diagnosis. The criterion for the completion of therapy is a negative PCR test of the cerebrospinal fluid.
- Interferons. In severe forms of encephalitis, it is advisable to combine immunomodulators with etiotropic antiviral medications. Interferons or interferon inducers are used to enhance the nonspecific resistance of the body.
- Glucocorticoids. They are mainly prescribed for the relief of cerebral edema. Hormones are also used in the case of recurrent herpes infection, in which an autoimmune process develops in the body.
- Diuretics. Medications are indicated for edema-swelling of the brain. Emergency dehydration is carried out with the help of the osmodiuretic mannitol or the saluretic furosemide. Oncodehydrants (albumin), glycerin solutions for probe injection into the stomach are also recommended.
- Anticonvulsants. The “first line” medicines for the elimination of convulsive syndrome are benzodiazepines. With their insufficient effectiveness, treatment is enhanced by drugs for anesthesia, barbiturates.
Vitamin complexes (B vitamins, ascorbic acid) in combination with antioxidants have a beneficial effect on the state of the central nervous system after suffering from herpes simplex encephalitis. Restorative treatment also includes nootropics and neurometabolic drugs to improve cognitive brain functions. Correction of the immunological status is carried out by adaptogens, actoprotectors, nonspecific immunomodulators.
To replenish the energy consumption of the body, stimulate reparative processes, enteral nutrition is shown to be adequate in terms of caloric content and vitamin composition. Much attention is paid to physiotherapy procedures, massage and physical therapy aimed at improving motor function. If there are indications, classes with speech therapists and speech pathologists are recommended.
Prognosis and prevention
Despite the etiotropic treatment, the prognosis for herpes simplex encephalitis remains unfavorable, the mortality rate is 15-20%. Most of those who have recovered still have neurological deficits. To prevent the disease, rational treatment of herpes of the skin and mucous membranes, timely counseling of patients with disseminated herpes infection is necessary.