A. Regarding the use of gadolinium-chelate, enhanced MR imaging is recommended for suspected MS for purposes of diagnosis and initial diagnostic evaluation.
There are several factors contributing to this recommendation. Confounding diagnoses may be less well visualized, or even missed, without contrast-enhanced MR imaging (leptomeningeal disease, meningioma, other mass lesions, vascular malformation). More important, the identification of enhancing lesions is an important component of the IP criteria providing evidence for disease DIT and DIS. Enhancing lesions at the time of a CIS are a strong independent predictor of future clinical attacks and a diagnosis of MS,10,20,21 probably as identification of an enhancing lesion is more likely with more active disease.
Conventional doses of gadolinium-chelate (0.1 mmol/kg, 20 mL maximum) are recommended with a minimum delay of 5 minutes following injection. Although it is well documented that greater doses (and delayed imaging) will increase lesion conspicuity and lesion number,22 for routine clinical care in an individual there is no evidence that supports higher doses at this time.
Although a greater dose of MR contrast may convert an individual from not MS to MS, to date there have been no formal tests of this strategy to predict MS. The cost of additional MR contrast is not inconsequential.
B. Enhanced MR imaging is considered optional for the baseline evaluation (in individuals already diagnosed with MS).
The standard of care is variable. Some MS neurologists routinely use enhanced MR imaging in their baseline assessment, but others do not. Enhancing lesions are a surrogate marker for focal disruption of the blood-brain barrier associated with macroscopic inflammation, an early (though probably not the earliest) stage in focal MS lesions. New enhancing lesions remain conspicuous from about 1 week through about 16 weeks, most <4 weeks.23 It is likely that inflammation is also microscopic (below MR imaging resolution), but there are no practical and no established quantitative methodologies for evaluating microscopic inflammation in vivo. There is controversy regarding inflammation in MS—notably related to “good” (potentially reparative) versus “bad” (proinflammatory, injurious) inflammation.24 Nevertheless, the current at least partially effective MS therapies are thought to exert much of their effect through anti-inflammatory mechanisms, and inflammation, dysfunction, and electrical disturbances are well correlated in functionally exquisite parts of the CNS, which suggests that much of the MR imaging–detected inflammation is undesirable. Inflammation is notably associated with axonal transection and other markers for axonal injury (amyloid precursor protein).25
C. Enhanced MR imaging is considered optional for the follow-up of MS.
Although the standard of care in many MS centers is to acquire routine enhanced MR imaging to aid in treatment decisions, there is insufficient evidence to conclude that enhancement alone should drive treatment decisions.
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