Objective Involuntary eyelid closure (IEC) may occur after deep brain stimulation of the subthalamic nucleus (STN-DBS) in Parkinson's disease (PD) and is often categorised as apraxia of lid opening (ALO), albeit the appropriateness of this term is under debate. To gain insight into the hitherto undefined pathophysiology of IEC after STN-DBS, we performed a comprehensive clinical and electrophysiological characterisation of lid function in a total of six PD patients.
Methods The study was carried out in six PD patients who developed IEC after STN-DBS. They underwent neurological examination and electromyography recording of activity in the orbicularis oculi muscle (OO) upon varying stimulation patterns. Intraoperative studies were performed in one patient.
Results Increasing STN-DBS intensity induced IEC in four patients, whereas it improved the condition in two. Needle EMG showed tonic hyperactivity of the OO in STN-DBS induced IEC, while variable patterns of OO activity (irregular and tonic) were seen in patients with STN-DBS-relieved IEC. Intraoperative analysis in one patient showed evidence for IEC being induced by activation of corticobulbar fibres.
Conclusions We identified two groups of IEC after STN-DBS based on clinical and EMG patterns: (1) STN-DBS induced IEC associated with tonic OO overactivity and (2) STN-DBS relieved IEC presenting with variable EMG patterns. Our findings provide relevant information on pathophysiology of STN-DBS related IEC and implications for its therapeutic management.
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Funding DW was supported by a research grant from Medtronic. JKP was supported by the Hertie-Foundation. AG has been funded by DFG GH 94/2-1, BMBF 16SV3783 and ERC 227632 grants. RK is supported by grants of the DFG (KR2119/3-1) and BMBF (01GS01834).
Competing interests FA has received speakers' honoraria and travel grants from Ipsen Pharma, Allergan and Merz Pharmaceuticals. TG has received speakers' honoraria from Novartis, Merck-Serono, Schwarz Pharma, Boehringer Ingelheim and Valeant Pharma, and research grants from Helmholtz Alliance for Health in an Ageing Society (HELMA).
Patient constent Obtained.
Provenance and peer review Not commissioned; externally peer reviewed.
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