Treat with IV Aciclovir if this is in the differential. Can cause a focal neurological deficit and appear identical to a temporal infarct in a patient who is otherwise well. Clues - pyrexia, cold sore, MRI changes, seizure, progression
- Most serious form is Herpes simplex encephalitis
- Other causes include West Nile virus
- HSV-1 has a predilection for the temporal lobes and less so frontal
- Invades brain parenchyma and may cause haemorrhagic necrosis
- There is haemorrhagic necrosis of the inferiomedial portion of the temporal lobe
- Disease begins unilaterally, then spreads to the contralateral temporal lobe
- Headache, Fever, Focal seizures and generalised seizures
- Cold sores on lips or mouth
- Altered consciousness, and abnormalities of speech and behaviour
- Hyperreflexia, coma, hemiparesis
- CT/MRI to exclude abscess will show lesions in the temporal lobes. May be necrosis and haemorrhage
- CSF - raised lymphocytes and elevated protein. Bloody CSF can result in a falsely negative PCR as the porphyrins can interfere with the assay
- HSV: also check enteroviral PCR or WNV (West Nile virus) if suspected.
- MRI - asymmetrical temporal lobe changes with HSV with inflammation, swelling and even necrosis
- EEG - slowing and periodic discharges
- Brain Biopsy - HSV encephalitis may show neuronal inclusion bodies called Cowdry Type A found in the nucleus
Poor prognostic indicators
- Age > 30, Coma at presentation, Bilateral EEG abnormalities
- High CNS viral load, Treatment delayed (4 days), abnormal CT
- If you have any suspicion of the diagnosis at all then treat with IV Aciclovir even if it turns out to be wrong. Untreated HSV is a tragedy.
- Treatment threshold must be very low initially. Studies show that Mortality was significantly reduced in Aciclovir-treated patients (28 percent versus 54 percent)
- IV Aciclovir 10 mg/kg TDS is given for 2-3 weeks.
- Monitor renal function, hydration and NG feeding as required.
- Often initially managed in HDU setting. Of those who survive there is a high risk of ongoing neurological deficits.
- There is no evidence base for steroids. Treat any seizures.
- For the most severe cases hemicraniectomy may be need for decompression
- Long term sequelae are seen in half of those treated such as poor memory, emotional lability, poor concentration, irritability, depression