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Infectious Disease - Encephalitis
ENCEPHALITIS
BASICS DESCRIPTION
Viruses, bacteria, fungi, and protozoa are among the infectious organisms that can cause encephalitis, which is an inflammation of the brain parenchyma that results in neurological symptoms. Any of these organisms can infect the central nervous system and cause encephalitis, mainly through hematogenous dissemination. Fever, disorientation, and headache are common initial symptoms, while seizures are also possible.
The incidence of epidemiology
• The elderly and the young are more likely to be affected by encephalitis.
• Herpes simplex virus (HSV) is the most frequent cause of viral encephalitis in the United States, accounting for 10% of all encephalitis cases. The most frequent cause in newborns is HSV-2, which is contracted during birth.
• Viral encephalitis's yearly incidence (the most
3.5–7.4/100,000 person-years (common etiology), with about 20,000 new cases annually.
RISK ELEMENTS
Age, season (i.e., HSV occurs irregularly throughout the year, while arboviruses are more prevalent in the summer and fall), immunological state, and potential exposures through travel, activities, and contact with animals and insects are risk factors.
OVERALL PREVENTION
• Transmission may be reduced by avoiding tick and mosquito bites.
• Vector control should be taken into consideration in regions where disease is on the rise.
• The risk of enteroviral infections may be reduced by avoiding swimming in ponds in the latter part of the summer.
• Those who live in or want to move to endemic areas should receive the Japanese encephalitis vaccine, which is already available.
• Disease can probably be avoided by avoiding mosquito bites.
• Measles, mumps, rubella, polio, and varicella vaccinations prevent these encephalitis-causing diseases.
Pathophysiology
The particular organism has a significant role in the pathophysiology of infection. Through hematogenous spread, viremia causes the reticuloendothelial system to be seeded, followed by distant locations like the central nervous system. Retrograde peripheral nerve transmission is the cause of infection in rabies encephalitis.
Ethiology
The most prevalent infectious etiology is viral. It is possible to identify no etiologic agent in as many as 75% of cases.
• Viral-Flaviviridae: Powassan virus, Russian spring-summer encephalitis, Central European encephalitis, West Nile virus, Japanese encephalitis virus, and St. Louis encephalitis virus
Togaviridae: Rubella virus, Venezuelan equine encephalitis, Western equine encephalitis, and Eastern equine encephalitis (EEE)
Bunyaviridae: Rift Valley fever, California, and La Crosse - Herpesviridae: HHV6, herpes B virus, varicella zoster virus (VZV), cytomegalovirus (CMV), and HSV The Paramyxoviridae family includes the Hendra, measles, mumps, and Nipah viruses. Other viruses that are frequently thought of include HIV and JC.
• • • •
influenza, mumps, rabies, adenovirus, enteroviridae (coxsackievirus, echovirus, and poliovirus), and Bacteria include Tropheryma whippelii (Whipple's illness), Mycobacterium tuberculosis, Mycoplasma, Listeria monocytogenes, Nocardia, Bartonella bacilliformis (Oroya fever), and Bartonella henselae (cat scratch disease). Ehrlichia chaffeensis (human monocytotropic ehrlichiosis), Coxiella burnetii (Q fever), Anaplasma phagocytophilum (human granulocytotropic ehrlichiosis), and Rickettsia rickettsii (Rocky Mountain spotted fever) are examples of ehrlichiosis and rickettsiosis. Spirochetes: Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease)
Fungal: Candida, Coccidioidomycosis, Cryptococcus neoformans, Aspergillus
Protozoa include Plasmodium falciparum (malaria), Acanthamoeba, Balamuthia mandrillaris, Toxoplasma gondii, and Naegleria fowleri. The trypanosomiasis caused by Trypanosoma brucei gambiense (West Africa) and Trypanosoma brucei rhodesiense (East Africa)
Helminths: Taenia solium (cysticercosis), Gnathostoma species, and Baylisascaris procyonis
History of Diagnosis
The history can be highly instructive, depending on the organism. For instance, the patient's immunological status, recreational activities, insect and animal exposures, travel history, and the incidence of specific diseases in the area can all assist to narrow the differential.
MEDICAL EXAMINATION
• Although a thorough skin examination should be performed to check for rashes, the neurological examination takes up the majority of the physical examination. It might be challenging to differentiate between meningitis and encephalitis due to the possibility of meningeal inflammation causing meningitis symptoms.
• Increased intracranial pressure may result in cranial nerve anomalies and early focal symptoms.
• When they appear, rashes are most useful for diagnosis. There might not be enough proof of tick or mosquito bites.
• Certain etiologies are linked to distinctive
physical manifestations: Lyme disease is linked to anomalies of the cranial nerves; Japanese encephalitis is linked to a movement problem resembling Parkinson's disease:
The temporal lobes are where HSV tends to localize, and patients can exhibit strange behavior as a prodrome.
Initial diagnostic and interpretation lab tests
• Although the white blood cell count (WBC) may be low in viral infections and elevated in bacterial infections, initial laboratory tests, such as the complete blood count (CBC) with differential, are not very useful.
• As soon as a non-contrast head CT scan or clinical examination rules out a space-occupying lesion, a lumbar puncture should be carried out.
• Cell counts, total protein, glucose, bacterial and viral cultures, fungal stain and culture, India ink stain, and HSV 1 and 2 as well as CMV and VZV should all be assessed using polymerase chain reaction (PCR) in cerebrospinal fluid (CSF).
• The usual CSF profile in viral encephalitis will show lymphocytic pleocytosis.
glucose, as well as increased protein. Malaria smears and WBC analysis for morulae in
• If there is a clinical suspicion that a patient may have ehrlichiosis or malaria, ehrlichia should be taken into consideration.
Cultures of non-CNS locations, such as blood, sputum, the nasopharynx, and stool, should be carried out as directed by clinical and epidemiologic guidelines. Serology is frequently used to make the diagnosis. It is important to get both acute and convalescent serologies. A range of PCR-based diagnostics are also available, and serologic testing can be performed in cases of Japanese encephalitis, dengue, and West Nile virus. • More CSF ought to be kept on hand.
Follow-up and Particular Points to Remember
It is recommended to closely monitor patients with specialists, such as those in infectious diseases and neurology.
Imaging To rule out imminent herniation, bleeding, and other problems, brain imaging should be done before lumbar puncture.
• The gold standard is a brain MRI, which every patient should get. For instance, in the instance of HSV
• Temporal lobe lesions, which can be unilateral or bilateral and hemorrhagic, are a characteristic finding in encephalitis. Gray matter involvement may be seen on MRI in cases with Japanese B encephalitis.
Hyperintense lesions in the brainstem are revealed by enterovirus-induced rhombencephalitis.
• When MRI is not accessible, brain CT should be performed. As a non-specific test, it is unable to distinguish between different etiological agents.
Diagnostic Techniques and Other
• The above-described lumbar puncture.
• In certain situations, EEG can be useful. For instance, EEG may show widespread slowing, focal temporal alterations, and PLEDS (periodic complexes and periodic lateralizing epileptiform discharges) in cases of HSV encephalitis. Alpha coma pattern, delta activity with spikes, and diffuse continuous delta activity are all linked to Japanese B encephalitis. Diffuse delta activity is linked to St. Louis encephalitis.
Pathological Results
• Inflammation of cortical arteries in the gray matter or at the gray–white matter junction is observed in viral encephalitis. Necrosis, demyelination, perivascular cuffing, and round cell infiltration are typical.
• There are several distinct histopathologic features for various etiologies, such as Japanese B encephalitis, necrosis in EEE, Negri bodies in rabies, and Cowdry type A inclusion bodies in HSV.
• Certain viruses may exhibit distinct patterns of dispersion. For example, HSV may typically be detected in the pons and temporal lobes, but it can also cause extensive lesions. The temporal lobes are also favored by rabies. The brainstem seems to be preferred by the West Nile virus.
DISTINCTIVE DIAGNOSIS
Acute disseminated encephalomyelitis (ADEM), encephalopathy, brain abscess, bacterial or viral meningitis, and Reye's syndrome
• Toxic metabolic abnormalities • Aseptic meningitis brought on by drugs including metronidazole, ibuprofen, and trimethrim–sulfamethoxazole
Vasculitis, vascular disorders caused by collagen, and paraneoplastic syndromes
MEDICAL CARE
Treatment for both HSV and bacterial meningitis should be part of empirical therapy until bacterial meningitis is ruled out. The empirical regimen should include doxycycline if rickettsial or Ehrlichia infection is suspected.
MEDICATION
• For 14–21 days, acyclovir 10 mg/kg is administered intravenously every 8 hours to treat HSV encephalitis. For neonates, higher doses—20 mg/kg intravenously every 8 hours—are advised.
• Ganciclovir is used to treat CMV encephalitis either by alone or in conjunction with foscarnet.
• HHV6 in immunocompromised hosts is treated with ganciclovir or foscarnet.
In the context of HIV, highly aggressive antiviral therapy (HAART) is recommended as an adjuvant treatment. Other targeted medicines are contingent upon the etiologic agent.
Considering the patient
Requirements for Admission
Hospitalization and specialized care, maybe including intensive care unit (ICU) level care, are necessary for patients suffering from encephalitis.
Intravenous Fluids
Because acyclovir is linked to kidney damage, patients should drink plenty of water while receiving treatment.
Continuing Care Follow-Up Suggestions
Patients' reactions to treatment should be regularly observed. Notably, recovery could be delayed or not happen at all, much like in the case of HSV encephalitis.
Monitoring of Patients
Clinical conditions determine the type and scope of patient monitoring. Long-term effects of the initial illness may be revealed by neuropsychological testing.
Depending on the etiological agent, the prognosis varies. For instance, early diagnosis and treatment commencement can significantly improve outcome in cases with HSV encephalitis. Poorer results are linked to delays in proper therapy.
• Untreated HSV encephalitis has a 70% fatality rate; with treatment, that number drops to 6–19%, with roughly half of survivors experiencing moderate to severe
impairment of the nervous system. Better results are linked to younger ages (less than 30).
COMPLICATIONS
Incorporate death, irreversible neurological impairments, and seizures. Although there is considerable disagreement about whether relapse is a result of a recurring viral infection or the host immune system's reaction to infection, it has been demonstrated that relapse occurs in 5–26% of patients with HSV encephalitis, with some cases perhaps being caused by insufficient therapy.
ENCEPHALITIS
BASICS DESCRIPTION
Viruses, bacteria, fungi, and protozoa are among the infectious organisms that can cause encephalitis, which is an inflammation of the brain parenchyma that results in neurological symptoms. Any of these organisms can infect the central nervous system and cause encephalitis, mainly through hematogenous dissemination. Fever, disorientation, and headache are common initial symptoms, while seizures are also possible.
The incidence of epidemiology
• The elderly and the young are more likely to be affected by encephalitis.
• Herpes simplex virus (HSV) is the most frequent cause of viral encephalitis in the United States, accounting for 10% of all encephalitis cases. The most frequent cause in newborns is HSV-2, which is contracted during birth.
• Viral encephalitis's yearly incidence (the most
3.5–7.4/100,000 person-years (common etiology), with about 20,000 new cases annually.
RISK ELEMENTS
Age, season (i.e., HSV occurs irregularly throughout the year, while arboviruses are more prevalent in the summer and fall), immunological state, and potential exposures through travel, activities, and contact with animals and insects are risk factors.
OVERALL PREVENTION
• Transmission may be reduced by avoiding tick and mosquito bites.
• Vector control should be taken into consideration in regions where disease is on the rise.
• The risk of enteroviral infections may be reduced by avoiding swimming in ponds in the latter part of the summer.
• Those who live in or want to move to endemic areas should receive the Japanese encephalitis vaccine, which is already available.
• Disease can probably be avoided by avoiding mosquito bites.
• Measles, mumps, rubella, polio, and varicella vaccinations prevent these encephalitis-causing diseases.
Pathophysiology
The particular organism has a significant role in the pathophysiology of infection. Through hematogenous spread, viremia causes the reticuloendothelial system to be seeded, followed by distant locations like the central nervous system. Retrograde peripheral nerve transmission is the cause of infection in rabies encephalitis.
Ethiology
The most prevalent infectious etiology is viral. It is possible to identify no etiologic agent in as many as 75% of cases.
• Viral-Flaviviridae: Powassan virus, Russian spring-summer encephalitis, Central European encephalitis, West Nile virus, Japanese encephalitis virus, and St. Louis encephalitis virus
Togaviridae: Rubella virus, Venezuelan equine encephalitis, Western equine encephalitis, and Eastern equine encephalitis (EEE)
Bunyaviridae: Rift Valley fever, California, and La Crosse - Herpesviridae: HHV6, herpes B virus, varicella zoster virus (VZV), cytomegalovirus (CMV), and HSV The Paramyxoviridae family includes the Hendra, measles, mumps, and Nipah viruses. Other viruses that are frequently thought of include HIV and JC.
• • • •
influenza, mumps, rabies, adenovirus, enteroviridae (coxsackievirus, echovirus, and poliovirus), and Bacteria include Tropheryma whippelii (Whipple's illness), Mycobacterium tuberculosis, Mycoplasma, Listeria monocytogenes, Nocardia, Bartonella bacilliformis (Oroya fever), and Bartonella henselae (cat scratch disease). Ehrlichia chaffeensis (human monocytotropic ehrlichiosis), Coxiella burnetii (Q fever), Anaplasma phagocytophilum (human granulocytotropic ehrlichiosis), and Rickettsia rickettsii (Rocky Mountain spotted fever) are examples of ehrlichiosis and rickettsiosis. Spirochetes: Treponema pallidum (syphilis) and Borrelia burgdorferi (Lyme disease)
Fungal: Candida, Coccidioidomycosis, Cryptococcus neoformans, Aspergillus
Protozoa include Plasmodium falciparum (malaria), Acanthamoeba, Balamuthia mandrillaris, Toxoplasma gondii, and Naegleria fowleri. The trypanosomiasis caused by Trypanosoma brucei gambiense (West Africa) and Trypanosoma brucei rhodesiense (East Africa)
Helminths: Taenia solium (cysticercosis), Gnathostoma species, and Baylisascaris procyonis
History of Diagnosis
The history can be highly instructive, depending on the organism. For instance, the patient's immunological status, recreational activities, insect and animal exposures, travel history, and the incidence of specific diseases in the area can all assist to narrow the differential.
MEDICAL EXAMINATION
• Although a thorough skin examination should be performed to check for rashes, the neurological examination takes up the majority of the physical examination. It might be challenging to differentiate between meningitis and encephalitis due to the possibility of meningeal inflammation causing meningitis symptoms.
• Increased intracranial pressure may result in cranial nerve anomalies and early focal symptoms.
• When they appear, rashes are most useful for diagnosis. There might not be enough proof of tick or mosquito bites.
• Certain etiologies are linked to distinctive
physical manifestations: Lyme disease is linked to anomalies of the cranial nerves; Japanese encephalitis is linked to a movement problem resembling Parkinson's disease:
The temporal lobes are where HSV tends to localize, and patients can exhibit strange behavior as a prodrome.
Initial diagnostic and interpretation lab tests
• Although the white blood cell count (WBC) may be low in viral infections and elevated in bacterial infections, initial laboratory tests, such as the complete blood count (CBC) with differential, are not very useful.
• As soon as a non-contrast head CT scan or clinical examination rules out a space-occupying lesion, a lumbar puncture should be carried out.
• Cell counts, total protein, glucose, bacterial and viral cultures, fungal stain and culture, India ink stain, and HSV 1 and 2 as well as CMV and VZV should all be assessed using polymerase chain reaction (PCR) in cerebrospinal fluid (CSF).
• The usual CSF profile in viral encephalitis will show lymphocytic pleocytosis.
glucose, as well as increased protein. Malaria smears and WBC analysis for morulae in
• If there is a clinical suspicion that a patient may have ehrlichiosis or malaria, ehrlichia should be taken into consideration.
Cultures of non-CNS locations, such as blood, sputum, the nasopharynx, and stool, should be carried out as directed by clinical and epidemiologic guidelines. Serology is frequently used to make the diagnosis. It is important to get both acute and convalescent serologies. A range of PCR-based diagnostics are also available, and serologic testing can be performed in cases of Japanese encephalitis, dengue, and West Nile virus. • More CSF ought to be kept on hand.
Follow-up and Particular Points to Remember
It is recommended to closely monitor patients with specialists, such as those in infectious diseases and neurology.
Imaging To rule out imminent herniation, bleeding, and other problems, brain imaging should be done before lumbar puncture.
• The gold standard is a brain MRI, which every patient should get. For instance, in the instance of HSV
• Temporal lobe lesions, which can be unilateral or bilateral and hemorrhagic, are a characteristic finding in encephalitis. Gray matter involvement may be seen on MRI in cases with Japanese B encephalitis.
Hyperintense lesions in the brainstem are revealed by enterovirus-induced rhombencephalitis.
• When MRI is not accessible, brain CT should be performed. As a non-specific test, it is unable to distinguish between different etiological agents.
Diagnostic Techniques and Other
• The above-described lumbar puncture.
• In certain situations, EEG can be useful. For instance, EEG may show widespread slowing, focal temporal alterations, and PLEDS (periodic complexes and periodic lateralizing epileptiform discharges) in cases of HSV encephalitis. Alpha coma pattern, delta activity with spikes, and diffuse continuous delta activity are all linked to Japanese B encephalitis. Diffuse delta activity is linked to St. Louis encephalitis.
Pathological Results
• Inflammation of cortical arteries in the gray matter or at the gray–white matter junction is observed in viral encephalitis. Necrosis, demyelination, perivascular cuffing, and round cell infiltration are typical.
• There are several distinct histopathologic features for various etiologies, such as Japanese B encephalitis, necrosis in EEE, Negri bodies in rabies, and Cowdry type A inclusion bodies in HSV.
• Certain viruses may exhibit distinct patterns of dispersion. For example, HSV may typically be detected in the pons and temporal lobes, but it can also cause extensive lesions. The temporal lobes are also favored by rabies. The brainstem seems to be preferred by the West Nile virus.
DISTINCTIVE DIAGNOSIS
Acute disseminated encephalomyelitis (ADEM), encephalopathy, brain abscess, bacterial or viral meningitis, and Reye's syndrome
• Toxic metabolic abnormalities • Aseptic meningitis brought on by drugs including metronidazole, ibuprofen, and trimethrim–sulfamethoxazole
Vasculitis, vascular disorders caused by collagen, and paraneoplastic syndromes
MEDICAL CARE
Treatment for both HSV and bacterial meningitis should be part of empirical therapy until bacterial meningitis is ruled out. The empirical regimen should include doxycycline if rickettsial or Ehrlichia infection is suspected.
MEDICATION
• For 14–21 days, acyclovir 10 mg/kg is administered intravenously every 8 hours to treat HSV encephalitis. For neonates, higher doses—20 mg/kg intravenously every 8 hours—are advised.
• Ganciclovir is used to treat CMV encephalitis either by alone or in conjunction with foscarnet.
• HHV6 in immunocompromised hosts is treated with ganciclovir or foscarnet.
In the context of HIV, highly aggressive antiviral therapy (HAART) is recommended as an adjuvant treatment. Other targeted medicines are contingent upon the etiologic agent.
Considering the patient
Requirements for Admission
Hospitalization and specialized care, maybe including intensive care unit (ICU) level care, are necessary for patients suffering from encephalitis.
Intravenous Fluids
Because acyclovir is linked to kidney damage, patients should drink plenty of water while receiving treatment.
Continuing Care Follow-Up Suggestions
Patients' reactions to treatment should be regularly observed. Notably, recovery could be delayed or not happen at all, much like in the case of HSV encephalitis.
Monitoring of Patients
Clinical conditions determine the type and scope of patient monitoring. Long-term effects of the initial illness may be revealed by neuropsychological testing.
Depending on the etiological agent, the prognosis varies. For instance, early diagnosis and treatment commencement can significantly improve outcome in cases with HSV encephalitis. Poorer results are linked to delays in proper therapy.
• Untreated HSV encephalitis has a 70% fatality rate; with treatment, that number drops to 6–19%, with roughly half of survivors experiencing moderate to severe
impairment of the nervous system. Better results are linked to younger ages (less than 30).
COMPLICATIONS
Incorporate death, irreversible neurological impairments, and seizures. Although there is considerable disagreement about whether relapse is a result of a recurring viral infection or the host immune system's reaction to infection, it has been demonstrated that relapse occurs in 5–26% of patients with HSV encephalitis, with some cases perhaps being caused by insufficient therapy.
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