How is PML diagnosed?

Many of the symptoms of PML are similar to those seen with other HIV-related diseases (e.g., toxoplasmosis, cryptococcal meningitis, and lymphoma of the central nervous system). Thus, it is important to determine the exact cause of these symptoms so that the correct treatment can be started.

Diagnosis is based partly on the symptoms being experienced, combined with an examination of the results of a magnetic resonance imagine (MRI) scan. Typically, lesions will show up as white or dark spots on the MRI. Most brain specialists can make a confident diagnosis based on the clinical exam and an MRI. The most accurate way to diagnose PML, however, is by conducting a brain biopsy. To do this, a surgeon will need to remove a small piece of brain tissue and send it to a lab for analysis. However, a brain biopsy can be risky, especially for those with compromised immune systems. It is also possible to diagnose PML by analyzing magnetic resonance imaging (MRI) scans of the brain and/or by looking for the JC virus in the fluid surrounding the spinal column. This requires a spinal tap—a needle inserted into the lower back to drain spinal fluid so that it can be analyzed.

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