Alleviation of off-period dystonia in Parkinson disease by a microlesion following subthalamic implantation
Clinical article
Object
A collision/implantation or microlesion effect is commonly described after subthalamic nucleus (STN) implantation for high-frequency stimulation, and this is presumed to reflect disruption of cells and/or fibers. Off-period dystonia, a frequent cause of disability in patients with advanced Parkinson disease, can lead to the need for surgical treatment. The authors assessed the early effect of this microlesion on off-period dystonia.
Methods
The authors assessed 30 consecutive patients with the advanced levodopa-responsive form of Parkinson disease. The patients' symptoms were Hoehn and Yahr Scale score ≥ 3, the mean duration of their disease was 11.4 ± 3.5 years, and they had undergone bilateral implantation of electrodes within the STN for high-frequency stimulation between February 2004 and December 2006. The microlesion effect was defined by the clinical improvement (Unified Parkinson's Disease Rating Scale [UPDRS] Part III score, UPDRS Part IV, item 35) assessed the morning of the 3rd day following STN implantation, after at least a 12-hour withdrawal of dopaminergic treatment and before the programmable pulse generator was switched on (off-drug/off-stimulation mode).
Results
Compared with baseline (off state), the microlesion effect improved the motor score (UPDRS Part III) by 27%. Subscores for tremor, rigidity, and bradykinesia respectively improved by 42, 37, and 25%. Nineteen patients (63%) suffered from off-period dystonia before surgery. Twelve (41%) reported complete relief of their symptoms in the immediate postoperative period and remained free of painful off-period dystonia throughout the 6-month follow-up period.
Conclusions
The author postulated that off-period dystonia alleviation may reflect both a microsubthalamotomy and micropallidotomy effect. They hypothesize, moreover, that the microlesion could play a role in the 6-month postoperative outcome.
Abbreviations used in this paper:
GPi = internal globus pallidus; PD = Parkinson disease; STN = subthalamic nucleus; UPDRS = Unified Parkinson's Disease Rating Scale.
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