From the Guidelines
EEG results are helpful in assessing brain function in patients with Herpes Simplex Virus type 1 (HSV-1) Encephalitis, as they can detect abnormal electrical activity, including periodic lateralized epileptiform discharges (PLEDs) in the temporal regions. The use of EEG in evaluating brain function in patients with HSV-1 encephalitis is supported by several studies, including a 2012 guideline by the Association of British Neurologists and British Infection Association, which states that EEG is abnormal in most patients with encephalopathy, including more than 80% of those with acute viral encephalitis 1.
Key Points to Consider
- EEG can be helpful in distinguishing whether abnormal behavior is due to a primary psychiatric disease or acute encephalitis.
- EEG is useful to identify non-convulsive or subtle motor seizures, which occur in both HSV encephalitis and other encephalopathies.
- In HSV encephalitis, EEG abnormalities include non-specific diffuse high amplitude slow waves, sometimes with temporal lobe spike-and-wave activity and periodic lateralized epileptiform discharges (PLEDs).
- A 2008 study by the Infectious Diseases Society of America also highlights the importance of EEG in evaluating patients with encephalitis, stating that EEG abnormalities can range from nonspecific generalized slowing to distinctive patterns suggestive of specific entities, including repetitive sharp wave complexes over the temporal lobes or periodic lateralizing epileptiform discharges in HSV-1 1.
Clinical Application
- EEG findings should be interpreted alongside other diagnostic tests like CSF PCR for HSV, MRI findings, and clinical presentation.
- Serial EEGs may be useful for monitoring treatment response and disease progression.
- While EEG findings are sensitive for encephalitis, they are not specific for HSV-1 as the cause.
- The most recent and highest quality study, a 2013 consensus statement by the International Encephalitis Consortium, also emphasizes the importance of EEG in evaluating patients with suspected encephalitis, stating that EEG abnormalities can be helpful in suggesting a specific etiologic diagnosis of encephalitis 1.
From the Research
EEG Results in Assessing Brain Function
- EEG results can be helpful in assessing brain function in patients with Herpes Simplex Virus type 1 (HSV-1) Encephalitis, as they can detect subtle or subclinical disturbances of cerebral function and allow monitoring of cerebral activity over time 2.
- Certain EEG phenotypes, such as lateralised periodic discharges, may indicate a specific pathophysiology, including HSV-1 encephalitis 2, 3, 4.
- EEG can be used to monitor the progression of the disease in patients with treatment refractory HSE, and may prompt escalation in therapy 4.
Prognostic Value of EEG
- EEG findings, such as absence of reactivity to auditory/noxious stimuli, can be associated with poor functional outcome in adult patients with severe herpes simplex encephalitis 5.
- Lateralized periodic discharges, seizures, and status epilepticus can be recorded in patients with HSV-1 encephalitis, but their presence may not always be associated with poor outcome 3, 6, 5.
- The prognostic value of EEG can be influenced by various factors, including the timing of the EEG recording, the presence of sedation, and the clinical context of the patient 5.
Clinical Applications of EEG
- EEG can be used to confirm or exclude non-convulsive seizures or status epilepticus, particularly in critically ill patients 2.
- EEG can be included in specialist guidelines for disease assessment, monitoring, and prognostication of various types of encephalitis, including viral and autoimmune encephalitis 2.
- Continuous EEG monitoring can provide valuable information on the progression of the disease and the response to treatment in patients with HSE 4.