Deep brain stimulation for tremor resulting from acquired brain injury.

OBJECTIVES: To evaluate the efficacy of deep brain stimulation (DBS) in the treatment of tremor resulting from acquired brain injury (ABI). METHODS: A series of eight consecutive patients with post-ABI tremor were treated with DBS of the ventro-oralis posterior (VOP)/zona incerta (ZI) region, and subsequently underwent blinded assessments using Bain's tremor severity scale. RESULTS: VOP/ZI DBS produced a mean reduction in tremor severity of 80.75% based on Bain's tremor severity scale, with significant reductions in all five component tremor subscores: rest, postural, kinetic, proximal and distal. No adverse neurological complications were reported, although one patient experienced exacerbation of pre-existing gait ataxia. CONCLUSION: VOP/ZI stimulation is demonstrated here to be an effective and safe approach for the treatment of post-ABI tremor in the largest series published at the time of writing.

Local field potentials reveal a distinctive neural signature of cluster headache in the hypothalamus.

Cluster headache (CH) is a debilitating neurovascular condition characterized by severe unilateral periorbital head pain. Deep brain stimulation of the posterior hypothalamus has shown potential in alleviating CH in its most severe, chronic form. During surgical implantation of stimulating macroelectrodes for cluster head pain, one of our patients suffered a CH attack. During the attack local field potentials displayed a significant increase in power of approximately 20 Hz. To the authors' knowledge, this is the first recorded account of neuronal activity observed during a cluster attack. Our results both support and extend the current literature, which has long implicated hypothalamic activation as key to CH generation, predominantly through indirect haemodynamic neuroimaging techniques. Our findings reveal a potential locus in CH neurogenesis and a potential rationale for efficacious stimulator titration.

Abnormal thalamocortical dynamics may be altered by deep brain stimulation: using magnetoencephalography to study phantom limb pain.

Deep brain stimulation (DBS) is used to alleviate chronic pain. Using magnetoencephalography (MEG) to study the mechanisms of DBS for pain is difficult because of the artefact caused by the stimulator. We were able to record activity over the occipital lobe of a patient using DBS for phantom limb pain during presentation of a visual stimulus. This demonstrates that MEG can be used to study patients undergoing DBS provided control stimuli are used to check the reliability of the data. We then asked the patient to rate his pain during and off DBS. Correlations were found between these ratings and power in theta (6-9) and beta bands (12-30). Further, there was a tendency for frequencies under 25 Hz to correlate with each other after a period off stimulation compared with immediately after DBS. The results are interpreted as reflecting abnormal thalamocortical dynamics, previously implicated in painful syndromes.

Reduction of common motoneuronal drive on the affected side during walking in hemiplegic stroke patients.

OBJECTIVE: The objective of this study was to use motor unit coupling in the time and frequency domains to obtain evidence of changes in motoneuronal drive during walking in subjects with stroke. METHODS: Paired tibialis anterior (TA) EMG activity was sampled during the swing phase of treadmill walking in eight subjects with unilateral stroke. RESULTS: On the unaffected side, short-term synchronization was evident from the presence of a narrow central peak in cumulant densities and from the presence of significant coherence between these signals in the 10-25 Hz band. Such indicators of short-term synchrony were either absent or very small on the affected side. Instead, pronounced 10 Hz coupling was observed. CONCLUSIONS: It is suggested that reduced corticospinal drive to the spinal motoneurones is responsible for the reduced short-term synchrony and coherence in the 10-25 Hz frequency band on the affected side in hemiplegic patients during walking. SIGNIFICANCE: This is of importance for understanding the mechanisms responsible for reduced gait ability and development of new strategies for gait restoration.

Local field potential beta activity in the subthalamic nucleus of patients with Parkinson's disease is associated with improvements in bradykinesia after dopamine and deep brain stimulation.

Parkinson's disease is treated pharmacologically with dopamine replacement medication and, more recently, by stimulating basal-ganglia nuclei such as the subthalamic nucleus (STN). Depth recordings after this procedure have revealed excessive activity at frequencies between 8 and 35 Hz (Brown et al., 2001; Kuhn et al., 2004; Priori et al., 2004) that are reduced by dopamine therapy in tandem with improvements in bradykinesia/rigidity, but not tremor (Kuhn et al., 2006). It has also been shown that improvements in motor symptoms after dopamine correlate with single unit activity in the beta range (Weinberger et al., 2006). We recorded local field potentials (LFPs) from the subthalamic nucleus of patients with Parkinson's disease (PD) after surgery to implant deep brain stimulating electrodes while they were on and off dopaminergic medication. As well as replicating Kuhn et al., using the same patients we were able to extend Weinberger et al. to show that LFP beta oscillatory activity correlated with the degree of improvement in bradykinesia/rigidity, but not tremor, after dopamine medication. We also found that the power of beta oscillatory activity uniquely predicted improvements in bradykinesia/rigidity, but again not tremor, after stimulation of the STN in a regression analysis. However improvements after STN stimulation related inversely to beta power, possibly reflecting the accuracy of the electrode placement and/or the limits of STN stimulation in patients with the greatest levels of beta oscillatory activity.