Abstract #1005

The relationship between diffusion MRI-derived axon diameters and conduction velocities in human peripheral nerves

Alexandru V. Avram¹, Zhen Ni², Felipe Vial², Amber Simmons³, Adam S. Bernstein^3,4, Giorgio Leodori⁵, Sinisa Pajevic⁶, Richard Coppola⁷, Mark Hallett², and Peter J. Basser³

¹National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD, United States, ²National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, MD, United States, ³National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, United States, ⁴Biomedical Engineering, University of Arizona, Tucson, AZ, United States, ⁵Clinical Center, National Institutes of Health, Bethesda, MD, United States, ⁶Center for Information Technology, National Institutes of Health, Bethesda, MD, United States, ⁷National Institute of Mental Health, National Institutes of Health, Bethesda, MD, United States

From diffusion-weighted MRIs with large q-values we estimated average axon diameters (AADs) in the median and ulnar nerves of healthy volunteers. We described signals using a tissue model of restricted and hindered diffusion and employed the multiple correlation function framework to account for all gradient pulses. Nerve conduction velocity distributions in the ulnar nerves were measured using electrophysiological techniques. Along these nerves, AADs correlated with average nerve conduction velocities supporting the linear dependence with propagation speed previously reported in the classical literature. This work presents pilot data suggesting the possibility of inferring inter-cortical latencies from whole-brain diffusion MRI.

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