Neuroradiology Case of the Week

Case 20

Natasha Buckshee, MD, and P-L Westesson, MD, PhD, DDS

Clinical Presentation: Patient is a 38-year-old male with a history of multiple sclerosis and worsening clinical symptoms.

Radiographic Findings: There are multiple high-signal (FLAIR) lesions in periventricular, subcortical white matter, the corpus callosum and along the callo-septal interface. The lesions radiate out from the ventricle into the white matter in a pattern that is characteristic for multiple sclerosis.

Figure 1: High-signal intensity in FLAIR images in deep white matter.	Figure 2: High-signal intensity in FLAIR images in deep white matter.
Figure 3: High-signal intensity in FLAIR images in periventricular white matter, this represents “Dawson’s Finger”.	Figure 4: High-signal intensity in FLAIR images in the callo-septal interface.

Diagnosis: Multiple sclerosis. Multiple matter lesions in characteristic deep white matter locations consistent with clinical history of multiple sclerosis.

Discussion:
   Multiple sclerosis (MS) is possibly due to autoimmune-mediated demyelination. It is the most common demyelinating disease (after vascular and age-related demyelination). There is a female preponderance with peak age between 20 and 40 years. Typical location is the callo-septal interface.
   The most typical course is a prolonged relapsing-remitting disease. Later, the disease often shifts into a chronic-progressive phase. A rare form is acute fulminant MS of the Marburg type and is associated with rapid clinical deterioration.

Imaging:

• An ovoid high-signal foci on T2WI.
• Periventricular extension (perpendicular to ventricles).
• Beveled or target (lesion within a lesion) appearance common on T1 and PD-weighted sequences.
• There is variable enhancement (solid, ring)
• Most lesions seen on MR are clinically silent

   Most MS plaques are iso- to hypointense on T1-weighted scans and hyperintense compared to brain on T2-weighted scans. Because there are many causes of white matter hyperintensities on T2WI, most authorities require the presence of three or more discrete lesions that are 5mm or greater in size, as well as lesions that occur in a characteristic location and have a compatible clinical history, to establish the MR diagnosis of MS. Periventricular extension of these lesions into the deep white matter, the so called "Dawson's finger" is characteristic. Enhancement represents blood brain barrier disruption, enhancement is variable and transient and is seen during the active demyelinating stage.

References:

1. Osborn, Anne G.: Diagnostic Neuroradiology, Mosby, 1994.