Natalizumab is an approved drug for the treatment of relapsing MS. Unfortunately, a rare but serious side effect of natalizumab treatment is the occurrence of progressive multifocal leukoencephalopathy (PML), an infection of the central nervous system due to a virus called the John Cunningham Virus (JCV).
As of 4 February 2014, a total of 437 cases of natalizumab-associated PML have been documented in more than 100,000 MS patients treated with natalizumab.
The diagnosis of PML is based on the clinical presentation and the identification of JCV antibodies in the cerebrospinal fluid and on the magnetic resonance imaging (MRI) scan.
The Journal of Neurology, Neurosurgery and Psychiatry has recently published an interesting study carried out in the Netherlands. The research team aimed to find advanced signs of MS on the MRI scans of patients treated with natalizumab, in the absence of clinical symptoms of PML.
They saw that asymptomatic natalizumab-associated PML indicators on MRI scans show rather localized lesions, frequently located in the frontal lobes, affecting the cortical grey matter and adjacent juxtacortical white matter.
This knowledge could assist in the diagnosis of natalizumab-associated PML at an asymptomatic stage, leading to a higher survival rate and improved functional outcomes.