Compared with controls, PD patients had: Increased variability in fibre size, increased % fibres with central nuclei, more angular small fibres, fibre atrophy and fibre type grouping (greater atrophy in patients with dysphagia), fast‐to‐slow shift in fibre types, more N‐CAM‐positive fibres indicating denervation. Here, NCAM1 is linked to Parkinson disease.