Routes of Entrance 1-Hematogenous: After systemic viral infection (e.g. arthropod borne viruses ) 2-Neuronal: Spread by axonal transport (e.g. HSV, rabies)
Viral Meningitis Viral Meningitis is an infection of the meninges and the subarachnoid space by viruses Etiology of Virus Meningitis 1-Enteroviruses ((coxsackieviruses, echoviruses ,polioviruses and human enteroviruses 68-71)) these are RNA viruses present in the GIT and causes 80-90% of cases and spread by feco-oral route.
2-Herpes simplex 3- Mumps virus 4- Influenza virus1 5- Varicella Zoster Virus Less Common Viruses 1- Epstien-Barr Virus. 2- HIV 3- lymphocytic choriomeningitis virus 4- Mollartet,s meningitis ( HSV type 2 )
Clinical Features Acute onset of headache, fever , irritability and rapid development of meningism . The headache is frontal or retroorbital with photophobia and pain on moving the eyes Focal neurological signs are rare .
constitutional symptoms include : malaise , myalgia , anorexia , nausea and vomiting , abdominal pain , and or diarrhea .
Investigations CSF examination showsWBCs 10-500/dl of lymphocytic type with normal glucose and protein level .CSF : PCR , culture , and serology , a specific cause can be found in 75 – 90 % of cases.
Management The patient treated symptomatically include use of analgesics , antipyretics and antiemetics. Fluid electrolyte status should be monitored . In patient with meningitis caused by HSV-1 or 2 and in cases of severe EBV and VZV meningitis , intravenous acyclovir ( 15 -30 mg/kg per day in three divided doses )
Which can be followed by an oral drug such as acyclovir ( 800 mg five times daily ) , famcyclovir (500 mg,tid) , or valacyclovir (1000 mg tid ) for a total course of 7 – 14 days
Viral Encephalitis Viral encephalitis is a diffuse or focal infection of the brain parenchyma caused by viruses
Etiology of viral encephalitisCOMMON : Herpes simplex type I and to less extend type II Varicella Zoster Virus Epstein – Barr virus Athropod-borne Viruses West Nile Virus
LESS COMMON : - Rabies - Eastern equine encephalitis virus - Western equine encephalitis virus - Cytomegalovirus - Enteroviruses - Mumps
Clinical features Acute onset of an almost universal triad of headache (in over 90% of cases) , fever , and alteration in mental status , preceded by symptoms of nonspecific mild illness. Changes in mental status at presentation may range from confusion, frank psychosis, or somnolence to stupor or coma. Temporal lobe involvement may result in seizures characterized by olfactory or gustatory aura or hallucinations.
Focal neurological signs (aphasia , hemiplegia ) . Seizues , involuntary movement like tremor Meningism present in many patient. Brainstem encephalitis : ataxia, dysartheria, diplopia or other cranial nerves palsies . Change in the level of consciousness may be present .
Herpes simplex viruses The commonest cause of sporadic cases of encephalitis, affect mainly temporal and frontal lobe . HSV type I reach the CNS through the trigeminal cranial nerve . HSV type II reach the CNS through hematogenous spread from genital tract infection
Investigations -CFS examination •Lymphocytic pleocytosis (25-500cell /dl)•normal glucose•normal or slightly elevated protein•PCR:- for detection of DNA or RNA
Of the viruses from the CSF and it is the most sensitive method for the diagnosis of CNS viral infection *Neuroimaging studies (MRI or CT scan of brain ) performed if the patient has any one of 1-ultered consciousness 2- seizure
3-focal neurological deficit 4-Atypical CSF profile *EEG: shows generalized slowing *Brain biopsy: for patient in whom the diagnosis was failed by other investigations.
Treatment of viral encephalitis 1- The patient require care in an intensive Care unit . 2- Vital functions , including respiration , Bp and ICP should be monitored continuously and supported as required 3- Fluid restriction , avoidance of hypotonic intravenous solutions , and suppression of fever . 4- Seizures should be treated with standard anticonvulsants .
5- Acyclovir 10mg/kg/8 hours in IV fluid not more than 7mg/ml over 1hours in patient with normal renal function for 14-21 days Side effect of acyclovir include: leukopenia, megaloblastic anaemia or thrombocytopenia and elevations in blood urea nitrogen and creatinine levels .
other antiviral -vidorabine -Foscarnet -Ganciclovir -cidofovir -ribavirin
Prognosis Young patient better than elderly patient consciouse patient better than comatose Sequelea :- -seizures -hemiplegia -coagnitive impairment
Slow Viral Infection of CNS 1-SUBACUTE SCLEROSING PANENCEPHALITIS SSPE SSPE occurs in children and adolescents usually many years after primary measles virus infection
Clinical features -Intellectual deterioration -apathy and clumsiness -myoclonic jerk -rigidity and dementia
Treatment : Inosiplex 100mg/kg/day alone or in combination with intrathecal or intraventricular alpha interferon but death ensures within years
2- Progressive Multifocal Lencoencephalopthy PML PML occurs due to infection of oligodendrocyte by human polyomavirus JC and HIV causing demyelination of cerebral hemispheres but sparing the spinal cord and optic nerve .
Clinical features Patients often present with visual deficits, typically a homonymous hemianopia ; mental impairment (Dementia, confusion, personality change ) ; weakness , including hemri- or monoparesis ; ataxia and aphasia.
Almost all patients have an underlying immunosuppressive disorders ; the most common associated conditions were AIDS , hematologic malignancies , transplant recipients , and chronic inflammatory diseases. Death within weeks or months.
3 - CRENTZFELDT-JAKOB DISEASE CJD GJD is a human transmissible spongiform encephalopathy . CJD caused by prion (abnormal protein ) . It could be : 1- Sporadic CJD, 85% - 90% cases . 2- Familial CJD, 10 % - 15 % .
Clinical features Middle aged to elderly ; rapid progressive dementia, myoclonus, visual disturbance, weakness and / or spasticity , extrapyramidal signs , ataxia and death within 4-6 months .
ACQUIRED IMMUNODEFICIENCY SYNDROME AIDS HIV can directly affect the nervous system or indirectly due to CD4 cell depletion.
Brain can be affected either I-Non focal lesions of brain 1-Acute HIV encephalitis 2-Aids dementia 3-Encephalitis due to HSV , CMV , varicella zoster virus. 4-PML
II-Focal lesions in the brain 1-Toxoplasma 2-Primary CNS lymphoma 3-Brain abscess 4-Tuberculoma 5-Vascular disorder 6- Neurosyphilis
Meninges Meningitis :HIV, TB, Cryptococcus, syphilitic Spinal cord -Transverse myelitis -Vascular myelopathy
Peripheral Nerves -Infection CMV, Varicella Zoster Virus -Non Hodgkin,s lymphoma -Polyneuropathy -Mononeuropathy Muscles: -Myositis , Myopathy