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Changes in cortical excitability with thalamic deep brain stimulation.
Neurology. 2005 Jun 14; 64(11):1913-9.Neur

Abstract

BACKGROUND

Deep brain stimulation (DBS) is an effective treatment for several movement disorders. However, its mechanism of action is largely unknown. Both lesioning and DBS of the ventralis intermedius (VIM) nucleus of thalamus improve essential tremor. Although DBS was initially thought to inhibit the target neurons, recent studies suggest that DBS activates neurons.

OBJECTIVE

To test the hypothesis that thalamic DBS activates the target area in patients with essential tremor.

METHODS

Cortical excitability was assessed in seven unmedicated patients with essential tremor using unilateral stimulators implanted in the VIM of the dominant hemisphere and in 11 healthy controls using transcranial magnetic stimulation (TMS). Patients were studied during optimal DBS (ON condition), half the optimal frequency (HALF), and with DBS off (OFF) in random order. Tremor was assessed after a change in DBS setting. Electromyography was recorded from the dominant hand, and TMS was applied over the contralateral motor cortex using single and paired pulses to elicit motor evoked potentials (MEPs). MEP recruitment was determined using stimulus intensities from 100% to 150% of motor threshold.

RESULTS

Tremor scores were significantly improved with DBS ON. Analysis of variance showed a significant interaction between condition (ON, HALF, OFF, Normal) and stimulus intensity on MEP amplitude. During DBS ON MEP amplitudes were significantly higher compared with controls at high but not at low TMS intensities.

CONCLUSION

Because the ventralis intermedius (VIM) projects directly to the motor cortex, the high motor evoked potential amplitude with deep brain stimulation ON suggests that VIM DBS activates rather than inhibits the target area.

Authors+Show Affiliations

Division of Neurology, Krembil Neuroscience Centre, Toronto Western Research Institute, University Health Network, University of Toronto, Toronto, Ontario, Canada.No affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info availableNo affiliation info available

Pub Type(s)

Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

15955943

Citation

Molnar, G F., et al. "Changes in Cortical Excitability With Thalamic Deep Brain Stimulation." Neurology, vol. 64, no. 11, 2005, pp. 1913-9.
Molnar GF, Sailer A, Gunraj CA, et al. Changes in cortical excitability with thalamic deep brain stimulation. Neurology. 2005;64(11):1913-9.
Molnar, G. F., Sailer, A., Gunraj, C. A., Cunic, D. I., Lang, A. E., Lozano, A. M., Moro, E., & Chen, R. (2005). Changes in cortical excitability with thalamic deep brain stimulation. Neurology, 64(11), 1913-9.
Molnar GF, et al. Changes in Cortical Excitability With Thalamic Deep Brain Stimulation. Neurology. 2005 Jun 14;64(11):1913-9. PubMed PMID: 15955943.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - Changes in cortical excitability with thalamic deep brain stimulation. AU - Molnar,G F, AU - Sailer,A, AU - Gunraj,C A, AU - Cunic,D I, AU - Lang,A E, AU - Lozano,A M, AU - Moro,E, AU - Chen,R, PY - 2005/6/16/pubmed PY - 2005/12/28/medline PY - 2005/6/16/entrez SP - 1913 EP - 9 JF - Neurology JO - Neurology VL - 64 IS - 11 N2 - BACKGROUND: Deep brain stimulation (DBS) is an effective treatment for several movement disorders. However, its mechanism of action is largely unknown. Both lesioning and DBS of the ventralis intermedius (VIM) nucleus of thalamus improve essential tremor. Although DBS was initially thought to inhibit the target neurons, recent studies suggest that DBS activates neurons. OBJECTIVE: To test the hypothesis that thalamic DBS activates the target area in patients with essential tremor. METHODS: Cortical excitability was assessed in seven unmedicated patients with essential tremor using unilateral stimulators implanted in the VIM of the dominant hemisphere and in 11 healthy controls using transcranial magnetic stimulation (TMS). Patients were studied during optimal DBS (ON condition), half the optimal frequency (HALF), and with DBS off (OFF) in random order. Tremor was assessed after a change in DBS setting. Electromyography was recorded from the dominant hand, and TMS was applied over the contralateral motor cortex using single and paired pulses to elicit motor evoked potentials (MEPs). MEP recruitment was determined using stimulus intensities from 100% to 150% of motor threshold. RESULTS: Tremor scores were significantly improved with DBS ON. Analysis of variance showed a significant interaction between condition (ON, HALF, OFF, Normal) and stimulus intensity on MEP amplitude. During DBS ON MEP amplitudes were significantly higher compared with controls at high but not at low TMS intensities. CONCLUSION: Because the ventralis intermedius (VIM) projects directly to the motor cortex, the high motor evoked potential amplitude with deep brain stimulation ON suggests that VIM DBS activates rather than inhibits the target area. SN - 1526-632X UR - https://www.unboundmedicine.com/medline/citation/15955943/Changes_in_cortical_excitability_with_thalamic_deep_brain_stimulation_ L2 - http://www.neurology.org/cgi/pmidlookup?view=long&pmid=15955943 DB - PRIME DP - Unbound Medicine ER -