|Case 17 :|
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The Bartel criteria establishes the diagnosis as "possible," "probable," or "definite". Using the Bartel method, three criteria must be met before the diagnosis of multiple sclerosis can be considered "definite":
(i) History of neurologic symptoms with relapse and remission;
(ii) Evidence of two or more anatomically separate lesions in the central nervous system obtained by clinical examination, electrophysiologic tests, or imaging techniques; and
Evidence of immunologic disturbance involving the central nervous
system revealed by a demyelinative spinal fluid profile.
Diagnosis of multiple sclerosis may be considered "probable" when there is evidence of two separate lesions in the central nervous system and when the patient satisfies only one of the two remaining essential criteria. Finally, patients with evidence of a single lesion or clinical deficit, but satisfying one or both of the remaining essential criteria, would be diagnosed as "possible" multiple sclerosis.
Acute MS (Marburg type) may also present as areas of clearly defined rings within or surrounding plaques of demyelination. These rings have signal characteristics on T1-weighted images consistent with the presence of paramagnetic material, with slight increase in signal intensity. Enhancement is typically seen in the region of these rings. This appearance most likely represents the presence of free radicals in the macrophage layer forming the margin of an acute plaque. Plaques of Balo concentric sclerosis are striking in their unique concentric rings of alternating destroyed and intact myelin.
In classic MS, the area of
inflammation decreases in size with time and leaves a smaller residual
plaque of high intensity, often more linear or punctate in appearance than
the initial lesion. Treatment with steroids may also be associated with a
marked reduction in lesion enhancement and morphology. High intensity
lesions in MS do not necessarily indicate demyelination, but rather might
merely reflect transient inflammation. Occasionally the plaque will
contain a cavity large enough to present as a fluid-containing cyst. With
progression of disease, atrophy is apparent, and increased iron deposition
is concomitantly found in the basal ganglia. Plaques are commonly situated
in the periventricular location, internal capsule, corpus callosum, pons,
and brachium pontis but may appear throughout the myelinated white matter
and not uncommonly in the gray matter. When the plaques are located in the
immediate periventricular region they may not be apparent on long TR/TE
images (where CSF is high intensity) and
"proton-density-weighted" (long TR/short TE) images will better
define the MS lesions as bright signal adjacent to darker CSF. Note that
the anatomic distribution of the lesions should not be considered key to
the diagnosis, since "exceptional" locations are in fact quite
The corpus callosum is a region
that is especially sensitive to demyelination with multiple sclerosis,
possibly due to its intimate neuroanatomic relationship to the lateral
ventricular roofs and its relationship to small penetrating vessels.
Sagittal MR imaging has been advocated for the depiction of the majority
of the corpus callosal lesions, although many can be clearly identified on
conventional axial images, particularly using proton-density-weighted
parameters. In up to 93% of MS patients, focal lesions can be identified
in the inferior aspect of the corpus callosum on sagittal views. Long TR
images typically show focal corpus callosal lesions to best advantage, but
the anatomic distortion with focal thinning in the inferior aspect of the
corpus callosum may be easily appreciated on T1-weighted lesions in many
Intracranial involvement with MS may appear quite similar to many other white matter diseases on MRI, with scattered foci of high intensity in the white matter on T2-weighted spin-echo images. Contrast enhancement may be used to add specificity to the finding of multiple hyperintensities on T2-weighted images, since the finding of enhancing along with nonenhancing lesions is quite common in MS but makes many other diagnoses unlikely. Similarly, the temporal changes in enhancing and nonenhancing lesions common in MS cases is very different from other entities. Periventricular lesions of MS commonly appear as linear abnormalities oriented perpendicular to the lateral ventricle, due to the propensity of MS plaques to occur in a periventricular location. Although this is common, the appearance of an MS lesion on MRI is highly variable and certainly not specific. MS can also appear as very subtle, diffuse hyperintensity in the white matter. Moreover, it has been shown by several studies that quantitative analysis of relaxation times in "normal appearing" white matter in MS patients differs from that of normal volunteers.