011-23 – Brainstem Morphometry and Deep Brain Stimulation Outcome in Cervical Dystonia

Background: Cervical dystonia is a movement disorder, characterised by involuntary head and neck muscle contractions. Although deep brain stimulation (DBS) of the globus pallidus internus (GPi) is an effective treatment option, clinical outcomes can vary even when sufficient targeting accuracy is achieved. Evidence indicates a role of brainstem dysfunction in cervical dystonia pathophysiology, but this has yet to be explored in relation to DBS outcomes.

Objective: To explore brainstem morphometry in relation to long-term clinical motor outcomes following DBS.

Methods: 26 patients with idiopathic cervical dystonia underwent bilateral targeting of the GPi and were separated into suboptimal and superior clinical outcome groups. A brainstem shape analysis was performed to assess surface changes and was additionally used as a seed to assess connectivity from a normative structural connectome. Brainstem nuclei and peduncular volumes were calculated between groups. Patient-specific electrode configurations were modelled to quantify the stimulatory overlap with the GPi to assess implantation accuracy.

Results: Inward deflation of brainstem shape was observed in patients with poorer responses. Fibre tracking from this area intersected cerebellar, pallidal and cortical motor regions. Cerebellar peduncle volumes, but not brainstem nuclei were observed to be significantly reduced in patients with poorer clinical outcomes. GPi implantation accuracy was not significantly correlated with clinical motor outcome.

Conclusions: Structural morphometry of the brainstem and cerebellar peduncles may mediate the potential efficacy of DBS on clinical motor outcomes. Brainstem changes appear to map onto whole-brain motor networks which may drive therapeutic response.