Abstract
BackgroundMacrodactyly is a congenital malformation characterized by aggressive overgrowth of multiple tissues, including subcutaneous fat, nerves, and bones in digits or limbs. In type II macrodactyly, the peripheral nerve is enlarged; however, the morphological and functional characteristics of the affected peripheral nerves have rarely been evaluated.MethodsIn this research, six macrodactyly patients and three polydactyly patients (control) were studied. Pre-operative sensory nerve action potential and intra-operative nerve action potential tests were performed. The microstructure and ultrastructure of the enlarged nerves were observed and neurofilament (NF) expression was evaluated using immunofluorescent staining.ResultsAxon impairment of the digital nerves originating from the median nerve (MN) was observed. A compensatory reinnervation from the ulnar nerve (UN) was found in two of the six patients, and significant morphological changes were observed in the enlarged nerve. The myelinated nerve fibers decreased, the lamellar structure of the myelin sheath changed, and the density of the NFs of the unmyelinated fibers decreased. There was aberrant distribution of NFs in the macrodactylous nerve tissues. In patients with compensatory UN reinnervation, the number of myelinated and unmyelinated fibers increased to normal levels; however, the diameter of the myelinated fibers apparently decreased.ConclusionsThe morphology and function of the macrodactylous enlarged nerve was impaired in type II macrodactyly patients; however, the unaffected UN partially compensated for the lost function of the affected MN under specific situations. Electrophysiological tests should be performed to determine the function of the affected nerve and surgical treatment for type II macrodactyly could be refined.
Highlights
Is characterized by excessive growth of multiple tissues including subcutaneous fat, nerve, and bone in digits or limbs, which the patient is tortured by the progression of the disease
The morphology and function of the macrodactylous enlarged nerve was impaired in type II macrodactyly patients; the unaffected ulnar nerve (UN) partially compensated for the lost function of the affected median nerve (MN) under specific situations
During the pre-operative electrophysiological test, we found that the sensory nerve action potentials (NAPs) amplitude in the index digits significantly decreased with prolonged latency (Fig 2A and 2E)
Summary
Is characterized by excessive growth of multiple tissues including subcutaneous fat, nerve, and bone in digits or limbs, which the patient is tortured by the progression of the disease. The multiple overgrowth of bone and soft tissue is often assessed by X-rays or magnetic resonance imaging (MRI) (Fig 1B and 1C); these methods are not sensitive to detect the nerve enlargement and functional damage. The results provided new information on morphological and neurophysiological impairment of the nerve in type II macrodactyly patients, and might help surgeons make the clinical decision on whether to excise the damaged nerves or preserve the functional compensatory nerve during the surgical procedure. Is a congenital malformation characterized by aggressive overgrowth of multiple tissues, including subcutaneous fat, nerves, and bones in digits or limbs. In type II macrodactyly, the peripheral nerve is enlarged; the morphological and functional characteristics of the affected peripheral nerves have rarely been evaluated
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