Objective: To find out how deep brain stimulation (DBS) impacts cortical auditory processing in advanced Parkinson’s disease (PD) patients.

Background: Motor symptoms of PD can be significantly alleviated by DBS. However, the mechanism of action of DBS is largely unclear. The short-term effect of DBS on cortical auditory processing in PD has been studied previously, but the long-term effect has remained unclear (1). We studied long-term DBS effect on cortical auditory processing in advanced PD patients.

Methods: Auditory evoked fields (AEFs) elicited with 1-kHz tones were recorded with magnetoencephalography (MEG) in 15 Parkinsonian patients before bilateral DBS implantation to subthalamic nuclei (STN) and after 6 months of DBS. At 6 months, MEG recordings were done both DBS on and off. The strong artefacts associated with DBS were suppressed by the signal subspace separation with temporal extension.

Results: The AEF at 100 ms (N100m) increased in amplitude, significantly (p = 0,040) over the hemisphere contralateral to the stimulated left ear. Simultaneously ipsilateral N100m amplitude diminished during follow-up, and the ipsi-contralateral hemispheric peak latency and amplitude difference significantly increased. The N100m latency shortened in the hemisphere contralateral to the stimulated ear and increased in the ipsilateral hemisphere during the follow-up. Turning DBS off at 6 months decreased N100m amplitudes in both hemispheres, whereas latencies were not affected. These differences were non-significant.

Conclusions: DBS treatment appears to excite cortical auditory processing contralaterally to the stimulated ear during follow-up of six months. Additionally, DBS seems to increase N100m latency difference between the hemispheres. These observations support the theory that STN DBS modulates the thalamocortical pathway by reducing thalamic inhibition and clearly modulates non-motor signal processing in Parkinson’s disease (2).

References: 1. Airaksinen K, Mäkelä JP, Taulu S, Ahonen A, Nurminen J, Schnitzler A, Pekkonen E. Effects of DBS on auditory and somatosensory processing in Parkinson’s disease. Hum Brain Mapp. 2011 Jul;32(7):1091-9. 2. Miocinovic S, McIntyre CC, Savasta M, Vitek JL. Mechanisms of Deep Brain Stimulation. In: Tarsy D, Vitek JL, Starr PA, Okum MS, editors. Deep Brain Stimulation in Neurological and Psychiatric Disorders. 1st ed. Totowa, NJ: Humana Press; 2008. p. 151-77.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/stn-dbs-modulates-cortical-auditory-processing-in-advanced-parkinsons-disease-a-meg-study/