Mixed results: Further studies needed on MRI accuracy in nerve disease

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Studies examining the diagnostic accuracy of MRI in distinguishing normal from abnormal extra-cranial nerves yield mixed results, according to a recent literature review published this month in the American Journal of Roentgenology.

The review was headed by Robert M. Kwee, MD, with Maastricht University Medical Center in The Netherlands. The team sought to look more into the increasingly common use of MRI to characterize, visualize and diagnose peripheral nerve disease.

“To our knowledge, however, no study has systematically investigated the accuracy of MRI in diagnosing extracranial peripheral nerve disease,” Kwee and colleagues said. “Therefore, the purpose of the current study was to systematically review the accuracy of MRI in distinguishing normal from abnormal peripheral nerves.”

Researchers queried PubMed/MEDLINE and Embase databases to find relevant studies on the performance of MRI in diagnosing nerve disease. The search resulted in a total of 1,908 articles from PubMed/Medline and 2,063 articles from Embase.

In the end, 33 articles were used in the literature review and investigated different types of nerves and used various criteria to diagnose peripheral nerve disease.

The researchers said a wide variation in sensitivities and specificities existed.

Kwee and team found the methodological quality of the studies to be moderate.

“Only 11 of the included studies investigated exclusively patients suspected of peripheral nerve disease,” the authors wrote.

Kwee and colleagues worried that fact might lead to overestimating studies’ accuracy,

“Indeed, overall accuracy (the relative diagnostic odds ratio) for the criterion of nerve T2-weighted or short T1 inversion recovery (STIR) hyperintensity was significantly lower for studies that included only patients suspected of peripheral nerve disease,” they wrote.

The authors noted that nerve T2-weighted or STIR hyperintensity, nerve enlargement and nerve flattening were most frequently used MRI criteria when studying abnormal peripheral nerves and these criteria were associated with the findings of reference standards in the studies.

“Clinical decision making using MRI should be done with care because there are no definitely established criteria that achieve high sensitivity and specificity for diagnosing peripheral nerve disease,” Kwee and colleagues concluded. “Well-designed studies performed only in patients suspected of peripheral nerve disease should further validate the utility of several MRI criteria for different nerves before implementing this technique in clinical practice.”