MRI and US of Normal and Abnormal Digital Nerves

Abstract

Digital nerves provide essential sensory innervation to the fingers and toes, playing a crucial role in tactile sensation and proprioception. Injury, inflammation, or entrapment of these nerves can result in sensory deficits, paresthesia, and neuropathic pain. Imaging the digital nerves is technically challenging due to their small caliber, adjacent and similarly appearing vascular bundles, and distal location in the extremities. Accurate evaluation requires detailed anatomic knowledge and optimized protocols using high-frequency US or MRI to ensure proper nerve visualization. Common pathologic conditions of digital nerves include traumatic injuries, inflammatory or infectious causes, compressive neuropathies caused by space-occupying lesions, and neoplastic lesions. Traumatic injuries are the most common digital nerve lesions, often requiring US to assess nerve continuity, caliber changes, and neuroma formation. MRI, including MR neurography, is especially useful in complex cases for evaluating nerves and associated soft-tissue or bone abnormalities. Although rare, neoplastic lesions, such as schwannomas and neurofibromas, are usually benign. Other tumorlike space-occupying lesions, including ganglion, lipoma, and hematoma, can cause nerve compression. The digital nerves of the foot are more commonly affected by trauma or interdigital neuromas, which represent a distinct entity characterized by perineural fibrosis rather than true neoplasia. The authors present a comprehensive case-based review of the digital nerves of the hands and feet, emphasizing anatomic considerations, proper imaging techniques with protocol suggestions, and key pathologic conditions. Readers can incorporate this knowledge into their practices for timely management of patients with digital nerve lesions.