The aim of this study was to summarize and appraise the existing evidence regarding magnetic resonance imaging (MRI) and functional magnetic resonance imaging (fMRI) findings in carpal tunnel syndrome (CTS) to identify possible altered brain structure and function.

CTS represents the most common nerve entrapment neuropathy in the arm associated with an altered nociceptive system peripherally and centrally.

Databases/search engines including Embase, Web of Science, Scopus, PubMed, and Cochrane were searched for relevant literature.  We included studies comparing MRI and fMRI findings in participants with chronic CTS and healthy controls regarding interdigit cortical representation distance and cluster size of digit representation on somatosensory cortex. When possible, the results from different studies were pooled and meta-analysis was performed using standardized mean difference (SMD) as effect size measures based on random effect model.

Among the included studies, there was a significant reduction of interdigit cortical separation distance of index-middle and index-little fingers in the CTS (SMD=-0.878, 95%CI (-1.27, -0.48), P-value <0.001) and (SMD=-0.84, 95%CI (-1.26, -0.42), P-value<0.001) respectively. However, middle-little fingers interdigit separation showed no significant difference (SMD=0.2, 95%CI (-0.9, -1.3), P-value =0.7).

In CTS, cluster size of index, middle and little fingers representation in the primary somatosensory cortex showed significant blurring as evident by increased their cluster size as well as reduction of interdigit cortical separation distance between both index-middle and index-little fingers. Altered cortical morphology and function proved that the central mechanisms might be involved in CTS building a base for future asserting studies and possible directed treatment strategies.