[Neuronal activity in the globus pallidus internus in parkinsonian patients with rigidity and bradykinesia]

Abstract

Objective: To investigate the neuronal activities in the globus pallidus internus (GPi) related to parkinsonian rigidity and bradykinesia

Methods: Twenty-six patients (M: 13 and F: 13) with parkinsonian syndromes of rigidity and bradykinesia, aged (58 +/- 11) with the duration of disease of (5.5 +/- 3.4) years, underwent pallidotomy. Their unified Parkinson's disease rating scale (UPDRS) motor score of rigidity was > or =5 (total score: 8) and the UPDRS score of bradykinesia was > or =9 (total score: 16) at "off" medication state pre-operationally. During operation, microelectrode recording in the GPi and electromyography (EMG) on the contralateral limbs to the surgery were performed. Single unite analysis and coefficient of variation (CV) of the interspike interval (ISI) were performed. The UPDRS motor score was assessed pre- and post-operationally. One-way ANOVA was carried out to study the firing rate as well as the ISI and CV of the ISI among different types of neuronal activity. Bonferroni test was conducted for means comparison.

Results: 10.1% (n = 24) of the total 237 GPi neurons (26 trajectories) showed discharge activity related to tremor (4-6 Hz), 57.4% (n = 136) of the neurons discharged tonic activity, and 32.5% (n = 77) neurons discharged irregular activity. Further analysis focused on 136 tonic active neurons and found that 75.7% (n = 103) of the neurons were characterized by a mean firing rate of (124.1 +/- 39.2) Hz with an ISI of (8.7 +/- 6.9) ms, and 24.3% (n = 33) of the neurons were characterized by a relative normal mean firing rate of (69.5 +/- 5.9) Hz with an ISI of (14.4 +/- 13.2) ms. The neurons with irregular neuronal activity had a mean firing rate of (30.2 +/- 9.8) Hz with an ISI of (35.6 +/- 36.8) ms. ANOVA revealed that there were statistically differences in the mean firing rate, ISI, and CV of the ISI for these neurons with relative normal tonic activity, high frequency tonic activity, and irregular activity (P < 0.01). UPDRS showed that the improvement of rigidity and bradykesia were 71.9% and 61.8% respectively.

Conclusion: High percent neurons with high frequency tonic activity and irregular neuronal activity observed in GPi suggest that the neuronal activity with altered rate and pattern may play an important role in parkinsonian symptoms such as rigidity and bradykinesia.