How is encephalitis diagnosed?
Diagnosis of encephalitis includes careful questioning to determine possible exposure to viral sources. Tests which can help confirm the diagnosis and rule out other disorders include:
A picture of the brain such as a CT scan or magnetic resonance imagining (MRI) is often done. MRI is the procedure of choice if herpes encephalitis is suspected.
A DNA study called polymerase chain reaction (PCR) has greatly improved the diagnosis of herpes encephalitis.
A reading of the electrical activity of the brain with an EEG can detect irregularities. Herpes encephalitis produces a characteristic EEG pattern.
A lumbar puncture, also known as a spinal tap, may be necessary to isolate the virus. During this procedure, the doctor applies local numbing medication and then inserts a needle into your lower back to collect fluid from the space around the spinal column for analysis.
The virus may also be isolated from tissue or blood.
A brain biopsy (surgical gathering of a small tissue sample) may be recommended in some cases where treatment to date has been ineffective and the cause of the encephalitis is unclear. Definite diagnosis by biopsy may allow specific treatment that would otherwise be too risky.