Is there a role for combined EMG-fMRI in exploring the pathophysiology of essential tremor and improving functional neurosurgery?
BACKGROUND
Functional MRI combined with electromyography (EMG-fMRI) is a new technique to investigate the functional association of movement to brain activations. Thalamic stereotactic surgery is effective in reducing tremor. However, while some patients have satisfying benefit, others have only partial or temporary relief. This could be due to suboptimal targeting in some cases. By identifying tremor-related areas, EMG-fMRI could provide more insight into the pathophysiology of tremor and be potentially useful in refining surgical targeting.


OBJECTIVE
Aim of the study was to evaluate whether EMG-fMRI could detect blood oxygen level dependent brain activations associated with tremor in patients with Essential Tremor. Second, we explored whether EMG-fMRI could improve the delineation of targets for stereotactic surgery.


METHODS
Simultaneous EMG-fMRI was performed in six Essential Tremor patients with unilateral thalamotomy. EMG was recorded from the trembling arm (non-operated side) and from the contralateral arm (operated side). Protocols were designed to study brain activations related to voluntary muscle contractions and postural tremor.


RESULTS
Analysis with the EMG regressor was able to show the association of voluntary movements with activity in the contralateral motor cortex and supplementary motor area, and ipsilateral cerebellum. The EMG tremor frequency regressor showed an association between tremor and activity in the ipsilateral cerebellum and contralateral thalamus. The activation spot in the thalamus varied across patients and did not correspond to the thalamic nucleus ventralis intermedius.


CONCLUSIONS
EMG-fMRI is potentially useful in detecting brain activations associated with tremor in patients with Essential Tremor. The technique must be further developed before being useful in supporting targeting for stereotactic surgery.
Department of Neurology/Clinical Neurophysiology, Academic Medical Center, Amsterdam, The Netherlands.
Maria Fiorella
MF
Contarino
Paul F C
PF
Groot
Johan N
JN
van der Meer
Lo J
LJ
Bour
Johannes D
JD
Speelman
Aart J
AJ
Nederveen
Pepijn
P
van den Munckhof
Marina A J
MA
Tijssen
Peter Rick
PR
Schuurman
Anne-Fleur
AF
van Rootselaar
D001931:Brain Mapping / Q000379:methods*; D004525:Efferent Pathways / Q000502:physiology; D004576:Electromyography / Q000379:methods*; D020329:Essential Tremor / Q000503:physiopathology* / Q000601:surgery*; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D010100:Oxygen / Q000097:blood; D013238:Stereotaxic Techniques; D013788:Thalamus / Q000601:surgery*
D010100:Oxygen