CNS infection: Encephalitis (hsv-1 = Viral!!!) Flashcards
Definition
Encephalitis describes inflammation of the brain parenchyma. The most common cause of encephalitis is herpes simplex virus-1 (95% of cases), which causes temporal and inferior frontal lobe encephalitis.
Epidemiology
Immunocompromise:
- numerous causes including extremes of age (children and the elderly),
- infection (such as HIV)
- medication (such as chemotherapy)
Risk Factors
Blood/fluid exposure: HIV and West Nile virus
Mosquito bite: West Nile virus
Transfusion and transplantation: CMV, EBV, HIV
Close contact with cats: toxoplasmosis
Aetiology
HSV (70%)
- HSV1(95%)
- HSV2
CMV
EBV
Mumps, rubella, measles
Fungal = cerebral aspergillosis
T cell lymphoma
Metabolic encephalopathy
Signs
Pyrexia
Reduced GCS
Focal neurological deficit, such as:
- Aphasia
- Hemiparesis
- Cerebellar signs
Symptoms
Fever
Headache
Behavioural changes:
- Memory disturbance
- Psychotic behaviour
- Withdrawal or change in personality
Confusion
Seizures
Diagnosis
Blood tests: FBC, CRP, U&Es and blood culture
Throat swab: culture for viral organisms
CT or MRI head: MRI is preferred and will show evidence of inflammation in the medial temporal and inferior frontal lobes in HSV encephalitis; CT is normal in ⅓ of cases
CSF investigations:
Analysis: lymphocytosis with raised protein in the case of viral aetiology
PCR: assays for common viral infections including HSV should be carried out
Culture: useful for bacterial causes
Serology: antibodies against specific viral antigens
Management
Antiviral medication:
- ACICLOVIR should be commenced empirically in all patients with suspected encephalitis
- Ganciclovir may be preferred in other herpesvirus infections, such as HHV-6
A combination of ganciclovir and foscarnet is usually used in CMV
Complications
Neurological sequelae: such as aphasia and neuropsychiatric issues
Seizures
Ischaemic stroke
Hydrocephalus
