Seeing big nerves in small children

Despite being a literally palpable clinical feature of some peripheral neuropathies, nerve enlargement is rarely studied systematically. Enlarged nerves can often be felt or seen, particularly in the neck, in the hereditary hypertrophic neuropathies, especially in Dejerine-Sottas disease and Charcot-Marie-Tooth disease type 1A (CMT1A). Even in affected children as young as 3 years, the authors have strongly suspected CMT1A when the child, and particularly a parent, has excessively large and easily palpable median nerves at the elbow, which approach or exceed the size of a standard pencil. Nerve hypertrophy is also encountered in Hansen disease, chronic inflammatory demyelinating neuropathy, nerve tumors, and certain focal nerve lesions. For the first time, Yiu et al.¹ have provided an analytical description of its distribution, evolution, and functional significance in children. Why has this taken so long? Unlike disease in other organs, disease in nerve and muscle has only been studied with the microscope—virtually never with the naked eye. Barring abscess or tumor, nerves and muscles are cut away at autopsy and most pathologists see nothing but tiny fragments from clinical donors. Even in the virtual world of MRI, most radiologists look past the nerves and muscles to seek out disease in other organs. However, placing high-resolution ultrasound in the hands of enterprising investigators such as Yiu et al. has for the first time made it possible not just to recognize nerve enlargement, but to measure it.