Peroperative transcranial sonography for electrode placement into the targeted subthalamic nucleus of patients with Parkinson disease: technical note

Abstract

Background In the search for a better preoperative knowledge of the position of probes and electrodes, we assessed the feasibility and the usefulness of transcranial sonography during surgery for the implantation of stimulation electrodes into the subthalamic nucleus (STN) of patients with Parkinson's disease. Methods Transcranial sonography was carried out during stereotactic surgery in 8 patients with Parkinson's disease who had a suitable temporal bone window on the side receiving the electrode. Test stimulation parameters were 130 Hz, 0.1 ms, up to 0 to 4.5 V. Results The test probe with a diameter of 0.8 mm was visualized through the temporal preauricular window. The correct anatomic position of the electrode tip could be indirectly assessed thanks to the topographic relationship of the STN with the hyperechogenic substantia nigra and the nucleus ruber. The tip position of the final electrode was easily documented. A laterality of 10.5 to 11.5 mm, verified by teleradiographic ventriculography and plain films, was correlated with the best response of symptoms of Parkinson's disease to electrical impulses delivered to the STN. Conclusions Transcranial sonography is easily feasible during stereotactic surgery. In combination with the clinical effects of electrostimulation on the symptoms of Parkinson's disease and with stereotactic x-ray images, it enables the assessment and the documentation of the correct position of implanted STN electrodes in real time.