Objective: To investigate whether altered neuronal activity in the subthalamic nucleus (STN) is associated with severity in patients with Parkinson’s disease (PD).

Background: PD is a progressive degenerative disorder. Its motor symptoms commonly start on one side of body and extend to the other side with advancing disease. The alteration in neuronal activity in the basal ganglia is thought to underlie the mechanism of PD.

Method: Thirty patients (M:19; F:11) who received bilateral STN DBS treatment were studied. Microelectrode recording in STN was performed. Single unit analysis including interspike interval (ISI) and coefficient of variation of ISI (CV) was carried out. Power spectral analysis was performed. UPDRS III was obtained. The severe symptoms (initiated body side) and the moderate symptoms (affected body side) were defined based on lateralized UPDRS III scores during “off” medication, disease duration, and the side of initial symptoms. For the severe symptoms group, the UPDRS III scores were≥20, the side of initial symptoms disease duration at≥8 year. The neuronal activity between two groups was compared.

Results: 271 neurons with mean firing rate (MFR) 41.2± 6.8 Hz identified from the severe symptoms group and 241 neurons with MFR 34.8± 6.6 Hz identified from the moderate symptoms group (p<0.001). Power spectral analysis showed 34.9% (84/241) ß oscillatory neurons in the moderate symptoms group and 51.3% (139/271) ß oscillatory neurons in the severe symptoms group (P<0.01). In contrast, there were 34.9% (84/241) tremor frequency oscillatory neurons in the moderate symptoms group and 21.4% (58/271) tremor frequency oscillatory neurons in the severe symptoms group (P<0.05). Further comparisons show that there were significant differences of MFR and CV between neurons (n=221) of the moderate and severe symptoms groups (MFR: 34.8±9.4 Hz vs 41.5±11.0 Hz P<0.01; CV: 1.07±0.02 vs.1.02±0.02, P<0.02).

Conclusion: The results suggest that subthalamic neuronal firing rate and proportion of ß oscillatory neurons increase with PD progression. This result is compatible with the rate theory of PD and could be due to loss of dopaminergic input to the striatum.

References: [1] M. S. Remple, C. H. Bradenham, C. C. Kao, P. D. Charles, J. S. Neimat, and P. E. Konrad. Subthalamic nucleus neuronal firing rate increases with Parkinson’s disease progression. Mov Disord. 2011, 26:1657-62. [2] L. A. Shreve, A. Velisar, M. Malekmohammadi, M. M. Koop, M. Trager, E. J. Quinn, et al.. Subthalamic oscillations and phase amplitude coupling are greater in the more affected hemisphere in Parkinson’s disease. Clin Neurophysiol. 2017,128:128-137.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/differences-in-subthalamic-oscillatory-neuronal-activity-associated-with-severity-in-parkinsons-disease/