C7 nerve root sensory distribution in peripheral nerves: a bold functional magnetic resonance imaging investigation at 9.4 T.

Introduction: In this study we used a rat model to elucidate the linear make-up of each major nerve of the upper limb by the C7 root through sensory stimulation and functional magnetic resonance imaging (fMRI).
Methods: The C7 nerve root and major nerves of the right forelimb were stimulated electrically. Blood oxygen level-dependent functional magnetic resonance imaging (BOLD fMRI) was performed concurrently. Voxel overlap within the primary sensory cortex was calculated.
Results: C7 comprised sensation in <1% in the musculocutaneous nerve, 6% in the ulnar nerve, 16% in the radial nerve, and 19% in the median nerve (P<0.005 for each). The overlap was always <25% for each major nerve.
Conclusions: This study helps explain why C7 is a suitable donor for brachial plexus injury treatment and why there is only a transient sensory deficit after transfer.