Does dominant pedunculopontine nucleus exist?

Sir,We read with great interest the paper by Fling et al. (2013) recently published in Brain . In this imaging study, patients with Parkinson’s disease with freezing of gait (FOG), without FOG, and age-matched controls were studied with diffusion tensor imaging to identify group and inter-hemispheric differences of tract quality and quantity in the pedunculopontine nucleus (PPN) network. Interestingly, patients with Parkinson’s disease with FOG had significantly less right PPN tract volume in terms of absolute values and ratio with the left side (i.e. greater laterality index) compared to patients without FOG. Furthermore, solely in the Parkinson’s disease with FOG group, linear regression analysis significantly correlated greater lateralization of PPN tract volume with poorer performance in action inhibition tasks. The authors concluded that right hemispheric circuitry might be uniquely involved in the pathophysiology of FOG (Fling et al. , 2013). In keeping with these findings, clinical evidence from the DATATOP cohort supports the notion …