Plaha P et al. (2006) Stimulation of the caudal zona incerta is superior to stimulation of the subthalamic nucleus in improving contralateral parkinsonism. Brain 129: 1732–1747

Deep brain stimulation is commonly used in the treatment of Parkinson's disease (PD). Although the subthalamic nucleus (STN) is the most usual target for stimulation, controversy exists over whether this is the optimum location. Plaha et al. now report high-frequency stimulation of the caudal part of the zona incerta nucleus (cZI) to be the most effective.

Between April 2002 and June 2004, 64 patients with medically refractory idiopathic PD underwent deep brain stimulation surgery, using a novel MRI-directed method of lead implantation; 17 patients had the best therapeutic contact in the postero-dorsal STN, 20 dorsomedial/medial to the STN (d/mSTN), and 27 posterior to the STN within the cZI. Patients were evaluated a median of 6 months after surgery. Following stimulation, the cZI group showed the most marked reductions in Unified Parkinson's Disease Rating Scale III motor score and adjusted 'off–on' rigidity score, as well as the greatest improvements in tremor and bradykinesia. The differences in dyskinesia scores, levodopa medication reduction and stimulation parameters were not statistically different between the groups; however, four patients in the d/mSTN group experienced adverse effects, and bilateral stimulation in these patients led to slurred speech and balance difficulties.

These results indicate that abnormal zona incerta activity could have an important role in PD. The data need replicating in larger randomized, controlled studies, but offer a potential improvement for the surgical management of PD.