Objective: To explore the patterns of neuronal activity in the basal ganglia nucleus in parkinsonian patients with levodopa-induced dyskinesia (LID).
Methods: Sixteen idiopathic parkinsonian patients, 11 males and 5 female: 5; aged 56.1 +/- 11.9, with the mean disease duration of (10.1 +/- 6.6). years and Hoehn & Yahr score ranging 2 -4, all with the symptoms of tremor, rigidity, and bradykinesia, 8 with severe LID [with the mean unified Parkinson's disease rating scale (UPDRS) IV score of 6.8 +/- 1.5] underwent pallidotomy (n = 8) or subthalamic nucleus (STN) deep brain stimulation (DBS) implantation (6 bilaterally and 2 unilaterally). Microrecording was performed in the globus pallidus internus (GPi) and STN. Electromyogram (EMG) on the contralateral limbs to surgery was simultaneously recorded. Single unit analysis was performed. The interspike interval (ISI) and coefficient of variation (CV) of ISI were calculated. One-way ANOVA and rank test were employed to compare the ISI and CV among the patients.
Results: Two hundred and thirty-eight neurons were identified from the GPi (n = 8) and STN (n = 14). 22.6% of them were tremor-related neurons, 33.8% were rapid tonic neuronal activity[ related, and 29.0% were irregular neuronal activity-related. It was discovered that 8. 0% of the neurons from GPi and STN were with grouped discharge following long period pause with the CV of 87 +/- 0.55, and 7.5% of the neurons were with low frequency firing with the mean frequency of (17.7 +/- 5.9) Hz. ANOVA revealed that in the STN the CV of the neurons with irregular with grouped discharge was significantly higher than those of the neurons with irregular neuronal activity and with low frequency firing (both P < 0.05), the ISI of the neurons with irregular grouped discharge was significantly higher than that of the neurons with low frequency firing and significantly higher than that of the neurons irregular neuronal activity (both P < 0.05); and in the GPi the CV of the neurons with irregular grouped discharge was significantly lower than those of the neurons with irregular neuronal activity and those with low frequency firing and the ISI of the neurons with irregular grouped discharge was significantly higher than those of the other groups (all P < 0.05). Chi square test showed that majority of the neurons with grouped discharge and neurons with low frequency firing mainly existed in the GPi and STN of the PD patients with LID (all P < 0.05).
Conclusion: The altered neuronal activity in the basal ganglia nucleus of GPi and STN plays an important role in the pathophysiology of PD and LID.