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30 Cards in this Set
- Front
- Back
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Viral encephalitis
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Cardinal signs and symptoms of encephalitis include headache, fever, alterations of consciousness (ranging from lethargy to coma), confusion, cognitive impairment, personality changes, motor weakness, seizures, movement disorders, accentuated deep tendon reflexes, and extensor plantar responses. Increased intracranial pressure can occur, manifested by papilledema, cranial nerve palsies, and progression to coma. Viral encephalitis is usually an acute illness, with or without a prodrome, but can also be a slowly progressive disease as in progressive multifocal leukoencephalopathy (PML) caused by JC virus, subacute sclerosing panencephalitis (SSPE) occurring after measles, and HIV encephalopathy.
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Viral meningitis
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Infection of the subarachnoid space caused by a virus. The predominant clinical features of fever, headache, and nuchal rigidity, are often accompanied by nausea, vomiting, and malaise. Viral meningitis is usually a self-limited illness which lasts 7-10 days. Viral meningitis can by caused by many viruses, including enteroviruses (most common), arboviruses, herpesviruses, acute HIV infection, and mumps.
Typical CSF findings in viral meningitis: mild to moderate increased in WBC (mainly lymphocytes), normal or slightly elevated protein concentration, and a normal glucose concentration. |
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Aseptic meningitis
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Occurrence of signs, symptoms, and a CSF profile suggesting meningitis in the absence of evidence of typical bacterial, parasitic, or fungal pathogens. Viruses are the most common cause of aseptic meningitis.
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Viral encephalitis
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Viral infection of the brain parenchyma. Symptoms include fever, headache, altered mental status, decreased level of consciousness, and focal neurological symptoms and signs which may include seizures, weakness, and speech disturbances. Typical CSF findings are similar to those found in viral meningitis. The most common causes of viral encephalitis in the U.S. are HSV-1, arboviruses, and enteroviruses.
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Viral encephalitis vs. meningitis
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The same viruses that produce meningitis also can produce encephalitis, but the specific viruses differ in the frequency with which they cause either syndrome. For example, HSV-2 more commonly causes meningitis than encephalitis, and HSV-1 (the most common cause of acute sporadic encephalitis in adults in the U.S.) more commonly causes encephalitis. Most arboviruses are more likely to produce encephalitis than meningitis.
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Meningoencephalitis
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Inflammation of the meninges and brain parenchyma. It is important to note that the presence of altered mental status or focal neurological signs or symptoms should prompt one to consider encephalitis or meningoencephalitis, as opposed to pure meningitis.
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Myelitis
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Inflammation of the spinal cord, which can cause symptoms of weakness, paralysis, sensory loss, and bowel and bladder disturbances. Poliomyelitis is the classic example of viral myelitis, but other viral causes of a myelitis include nonpolio enteroviruses, herpesviruses, retroviruses, and West Nile virus.
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Meningoencephalomyelitis
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Meningitis, encephalitis, and myelitis may all occur
together during an infection |
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CSF findings of CNS infections
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Normal:
0-5 WBC 50-75 Glucose 15-40 Protein Bacterial meningitis Increased CSF pressure Elevated WBC (100-100000, >80% PMNs) Decreased Glucose (<40) Increased Protein (100-1000) Viral meningitis/encephalitis No change in CSF pressure Increased WBC (10-500, mainly lymphocytes) Normal glucose (low in LCM, HSV, mumps) Normal or slightly elevated protein (50-100) |
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Neurotropism
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the ability of a virus to infect neural cells
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Neuroinvasiveness
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the ability of a virus to enter the central nervous system (CNS)
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Neurovirulence
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the ability of a virus to cause disease of nervous tissue once it enters the CNS
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Viral encephalitis
Treatment |
Treatment supportive except acyclovir for HSV
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HSV encephalitis
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HSV encephalitis
Clinical |
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HSV encephalitis
Diagnosis |
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HSV encephalitis
Treatment |
Acyclovir is well-tolerated and reduces mortality from 70% to 19% and should be started EARLY
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Arboviruses
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Arthropod-borne viruses
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Arboviral encephalitis
Pathogenesis |
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West Nile virus
Clinical |
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West Nile virus
Diagnosis |
Most sensitive screening test is IgM ELISA in CSF and/or serum
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West Nile virus
Treatment |
Supportive; experimental interferon, ribavirin, immunoglobulin
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Arboviral encephalitis
Clinical symptoms |
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Arboviral encephalitis
Examples |
Togaviridae - Alphavirus (ssRNA+, env) - Western and Eastern Equine
Flavivirdae - Flavivirus (ssRNA+, env) - Japanese encephalitis, St. Louis encephalitis, Rabies, Dengue, Yellow fever Bunyaviridae - Bunyavirus (ssRNA-, segmented, env) - LaCrosse, California encephalitis |
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Rabies virus
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Rhabdoviridae family, Lyssavirus genus
Nonsegmented negative sense, single-stranded RNA, enveloped |
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Rabies virus
Pathogenesis |
1. Virus innoculated by bite
2. Viral replication in muscle and muscle spindle 3. Virus enters peripheral nervous system via nerve innervating muscle spindle 4. Passive ascent via sensory fibers 5. Replication in dorsal ganglion 6. Rapid ascent in spinal cord 7. Infection of spinal cord, brainstem, cerebellum, and other brain structures 8. Descending infection via nervous system to eye, salivary glands, skin, and other organs |
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Rabies virus
Clinical features |
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Rabies virus
Diagnosis |
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Rabies virus
Treatment |
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Rabies virus
Prevention |
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