Electrophysiological study of symptomatic improvement by subthalamic stimulation on patients with Parkinson's disease

Abstract

To investigate the correlation of the neuronal activity in the subthalamic nucleus (STN), active contacts of deep brain stimulation (DBS), and clinical outcome of Parkinson's disease (PD). Nineteen patients with PD, 12 males and 17 females, aged (61 +/- 8), received STN DBS. Simultaneously microelectrode recording was performed in the STN and electromyography (EMG) was conducted on the selected muscles of contralateral limb during the surgery. Single unit analysis and cross-correlation test were carried out to study the neuronal pattern-related parkinsonian symptoms. All patients were evaluated with the unified Parkinson's disease rating scale (UPDRS) in "off" state pre- and post-operatively. Two hundred and seventy-eight STN neurons were identified in 29 trajectories. Among these neurons, 35 (12.6%) fired at the same frequency as the tremor (R = 0.7, P < 0.01) and was defined as "tremor cell"; 91 (32.7%) fired rapid tonic discharge, and 152 (54.7%) fired irregular neuronal discharge. Majority of the tremor cells (74.3%, 26/35) were localized at the dorsal part of STN, while majority of the tonic discharge cells (59.3%, 54/94) and irregular discharge cells (65.1%, 99/152) were distributed in the ventral part of STN were localized at the ventral part of STN (all P < 0.05). UPDRS showed that the tremor improvement rates of the stimulation contacts from those at the lower part to the those at the upper part of STN (0/4, 1/5, 2/6, and 3/7) were 50.0%, 68.9%, 83.2%, and 87.4% respectively; the clinical rigidity improvement rates were 84.6%, 82.4%, 69.7%, and 55.2%; and the clinical bradykinesia improvement rates were 66.1%, 57.0%, 54.1%, and 42.1% respectively. Different patterns of neuronal activity in STN are likely to associate with parkinsonian symptoms. The results provide the helpful information for selection of contacts of DBS and surgical therapy.