Corneal confocal microscopy demonstrates varying degrees of neurodegeneration in atypical parkinsonian disorders

Objective: We have used corneal confocal microscopy (CCM) to identify corneal nerve loss as a potential marker of neurodegeneration in participants with Parkinson's disease (PD), multiple system atrophy (MSA) and progressive supranuclear palsy (PSP).Methods: Patients with PD (n = 19), PSP (n = 11), MSA (n = 8) and healthy controls (n = 18) underwent neurological assessment and CCM.Results: Corneal nerve fibre density was significantly lower in participants with PD (p = 0.005), PSP (p = 0.005) and MSA (p = 0.0003) compared to controls. Corneal nerve branch density was significantly lower in participants with PD (p = 0.01) and MSA (p = 0.019), but not in participants with PSP (p = 0.662), compared to controls. Corneal nerve fibre length was significantly lower in participants with PD (p = 0.002) and MSA (p = 0.001) but not in participants with PSP (p = 0.191) compared to controls.Conclusion: CCM detects corneal nerve loss in participants with PD and MSA and to a lesser extent in PSP compared to healthy controls.