Unilateral subdural motor cortex stimulation improves essential tremor but not Parkinson's disease

Abstract

Epidural motor cortex stimulation has been reported to be effective in treating some movement disorders. Nevertheless, clinical results have been variable and no double-blinded evaluations have been reported. The aim of this study was to investigate efficacy and safety of unilateral subdural motor cortex stimulation in patients with essential tremor and Parkinson's disease. Six patients with essential tremor and five parkinsonian patients were selected. Craniotomy was performed under local anaesthesia with conscious sedation. A four contact electrode (Resume II model 3587, Medtronic, Inc) was positioned on the motor cortex, after identification of the area with direct monopolar cortical stimulation. Soon after surgery, a variety of different settings of stimulation were assessed using standard rating scales to select the optimal stimulation parameters. The effects of chronic stimulation were evaluated in both groups of patients after 3 months (double-blinded fashion) and 1 year (open fashion). In essential tremor, contralateral hand tremor scores significantly improved (P = 0.04) with stimulation during the double-blinded study, whereas in Parkinson's disease, there were no changes in the OFF medication/on stimulation motor scores compared with off stimulation. At 1 year, tremor was improved by stimulation in two out of three patients with essential tremor available at follow-up, whereas no improvement was observed in the five parkinsonian patients. One parkinsonian patient had a cortical venous infarct. Three other patients had self-limiting seizures with aggressive trials of stimulation in the period of dosage selection. These findings suggest that unilateral subdural motor cortex stimulation may be useful for contralateral hand tremor in selected patients with essential tremor but was not effective in improving parkinsonian signs in our series.

Resting-state networks link invasive and noninvasive brain stimulation across diverse psychiatric and neurological diseases

“…4A, graph). In other diseases, evidence that a specific site of noninvasive stimulation is ineffective is not as strong; however, in general, stimulation of cerebellum appears to be more effective for essential tremor than stimulation of M1 (53)(54)(55)(56)(57), stimulation of M1 appears to be more effective for pain than stimulation of DLPFC (58)(59)(60)(61), and stimulation of the left DLPFC appears to be more effective for depression than stimulation of the cranial vertex (top of the head) (17). In all cases, the DBS site with the best evidence of efficacy was significantly more connected to the sites where noninvasive stimulation was effective than to sites where noninvasive stimulation was ineffective, with connectivity to the ineffective site falling at or below the connectivity to random sites (Fig.…”

“…Invasive cortical stimulation involves the surgical implantation of an electrode on the surface of the brain. The current results are likely to be pertinent to this technique, because the sites of cortical implantation tend to be the same targets used for noninvasive stimulation, including M1 in Parkinson's disease (129,130), M1 in essential tremor (54), premotor cortex in dystonia (131), left DLPFC in depression (132), cerebellum in epilepsy (133), and M1 in pain (61). Other noninvasive brain-stimulation modalities include electroconvulsive therapy and vagal nerve stimulation, which show therapeutic effi- (table).…”

Recent Advances in Essential Tremor

“…When compared to DBS, superficial cortical stimulation is less complex to perform and has a lower incidence of cerebral haemorrhage. However, adverse events such as sensory effects, contraction of the contralateral fingers and seizures can limit its clinical use [45].…”

Noninvasive Measurement of Cortical Activity During Effective Brain Stimulation For Movement Disorders

“…Despite these data, attempts at epidural motor cortex stimulation (EMCS) in humans with Parkinson disease and essential tremor in small case series have shown mixed results, with a recent blinded study, suggesting that it may improve symptoms of essential tremor, but not Parkinson disease [14]. Although the small sample sizes and potential technical/methodological differences of the various EMCS studies make them difficult to reconcile with one another, they raise the possibility that the cortical physiology associated with subthalamic and thalamic DBS in our recent work might be unrelated to its therapeutic mechanism.…”

“…While this is possible, these subcortical DBS targets are small, dense functional nodes in the motor network that receive projections from multiple cortical regions, while EMCS activates the cerebral cortex less discriminately over a larger volume. This has lead authors to question whether EMCS influences neuronal activity efficiently enough to exert meaningful behavioral effects [14]. Regardless of whether EMCS sufficiently influences primary motor cortex activity, it still may not act on adjacent cortical regions such as the premotor, supplementary motor and parietal areas (regions with known projections to the subthalamic nucleus and thalamus).…”