Complications
Mortality varies according to the underlying aetiological agent. Untreated herpes simplex virus (HSV) encephalitis has a mortality of around 70%, with early treatment reducing this to approximately 10%.[8][133] Older age and depressed levels of consciousness (Glasgow Coma Scale <6) are poor prognostic indicators. Rabies and amoebic encephalitis are almost universally fatal. High mortality is seen with Eastern equine encephalitis, Japanese encephalitis, Nipah virus, and viral haemorrhagic fevers. HIV infection forebodes higher mortality rates in encephalitis.[8]
Early treatment with aciclovir and adequate supportive critical care can decrease mortality associated with HSV encephalitis. For other cases, in addition to specific treatments if available, good supportive critical care medicine is advocated and there is some indirect evidence that this is associated with decreased mortality.
Syndrome of inappropriate secretion of antidiuretic hormone (SIADH), diabetes insipidus (DI), loss of temperature control, and vasomotor instability can occur in patients with encephalitis.
SIADH: avoidance of hypotonic fluids and fluid restriction (if possible).
DI: maintenance of normovolaemia and use of desmopressin.
Hyperthermia: antipyretics or cooling devices are used to maintain normothermia, as hyperthermia is associated with worse functional outcomes.
Vasomotor instability: monitored in an intensive care unit setting with adequate intravenous access and cardiac and blood pressure monitoring. Treatment is tailored to stabilise these parameters, with the institution of advanced cardiac life support protocols as required.
Depending on the extent and severity, worsens the outcome. Antiplatelet or anticoagulant agents can be considered.
Herpes simplex virus (HSV) encephalitis can trigger autoimmune encephalitis that leads to neurological worsening.[134] Prospective studies suggest 23% to 27% of patients with herpes simplex encephalitis develop autoimmune encephalitis.[134][145] Post-HSV-autoimmune encephalitis usually presents within 2 months of treatment of herpes simplex encephalitis; the symptoms are age-dependent, and the neurological outcome is worse in young children.[134][145] These patients may respond to immunotherapy.[59]
Occurs after 6 months. An extrapyramidal syndrome characterised by somnolence, fatigue, and ophthalmoplegia was seen after the influenza epidemic of 1918. Occasional cases are now reported after sporadic viral encephalitis, especially Japanese encephalitis.[146]
Neurological sequelae occur within one month and include abulia, akinetic mutism, aphasia, amnesia, neuropsychiatric issues, and motor problems. ADHD and cognitive issues can be seen in children.[127][140][141] Acute rehabilitation services, speech language therapy, and neuropsychiatric services should be provided for these patients.
A frequent component of encephalitis and a consequence of the extensive inflammatory reaction that is integral to encephalitis. The formation of gliotic scars marks the healing phase and can lead to the formation of epileptogenic foci. A neurology consultation is highly recommended for all patients with ongoing seizures.
Status epilepticus is defined as 5 or more minutes of either continuous seizure activity or repetitive seizures without regaining consciousness.[142][143] Treatment involves a stepwise medication approach aimed at aborting the clinical and electrographic seizures. It carries a high mortality rate and may cause serious complications if not promptly treated.
Management is best done in consultation with a specialist in neurocritical care or neurology. Seizures can occur in the long term and need to be treated with standard anticonvulsant drugs in consultation with a neurologist. See Status epilepticus.
Sleep disorders in patients with autoimmune encephalitis include parasomnia, insomnia, hypersomnia, and sleep-disordered breathing.[147][148] These can be acute and severe, and can often persist beyond the initial stage of the disease.[149] Untreated sleep disturbances may worsen autonomic instability, thereby challenging attempts to wean patients from mechanical ventilation. Over the long term, sleep disorders may compromise recovery and return to meaningful function.[150] Because sleep disorders are often overshadowed by other neurological and psychiatric symptoms, patients and caregivers should be specifically questioned about new-onset sleep disruption or behaviours.[150]
Depending on the extent and severity, worsens the outcome. Haemorrhages are usually medically managed with supportive care and monitoring of blood pressure. Larger bleeds may require surgical interventions.
Depending on the extent and severity, worsens the outcome. The treatment of cerebral vein thrombosis is difficult, as anticoagulant use can increase the risk of haemorrhage.
Can develop as a late complication with bacterial, fungal, and parasitic encephalitis. This is due to the decreased efficiency of absorption of cerebrospinal fluid from arachnoid granulations. Placement of a draining ventricular catheter/ventriculoperitoneal shunt should be considered.
The syndrome of prolonged and persistent fatigue, myalgia, difficulty in concentrating, and post-exertional malaise is sometimes seen after viral encephalitis.[144] No specific treatments exist for this condition, but a multidisciplinary approach is advocated.
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