Indolent course of progressive multifocal leukoencephalopathy during natalizumab treatment in MS

Case report.

In September 2002, a 30-year-old previously healthy woman presented with walking difficulties. Neurologic examination showed a bi-pyramidal syndrome, ataxia, and sensory disturbance in all extremities. After MRI of the brain and cervical spinal cord, which showed multiple typical T2-weighted white matter lesions, diagnosis of a clinically isolated syndrome suggestive of a first episode of MS was established.

In January 2003, the patient started interferon-β-1a, which she discontinued in October 2003 because of depressive symptoms. From March 2004 until December 2006, she used glatiramer acetate. Still, several clinical relapses occurred.

In March 2007, the patient started natalizumab infusions. She had no clinical exacerbations since. Routine MRI of the brain 1 year later showed no active lesions.

A second MRI in February 2009 was initially interpreted as showing no new lesions. In retrospect, subtle and diffuse abnormalities were visible in cortical and subcortical areas (figure). Since June 2009, she had mild progressive cognitive problems. For example, she made repetitive phone calls up to 6 times a day and was forgetting appointments. For that reason, in October 2009, a new MRI was performed, showing a new pontine lesion and progression of the diffuse abnormalities in both hemispheres (figure).