Postural tremor in Wilson's disease: A magnetoencephalographic study

Abstract

The following study included 5 Wilson's disease (WD) patients showing a right-sided postural forearm tremor (4-6 Hz) and addressed the question of whether the primary motor cortex (M1) is involved in tremor generation. Using a 122-channel whole-head neuromagnetometer and surface electromyogram (EMG), we investigated cerebromuscular coupling. Postural tremor was observed in a sustained 45-degree posture of the right-sided forearm. Data were analyzed using dynamic imaging of coherent sources (DICS), revealing cerebromuscular coupling between EMG and cerebral activity. Coherent sources were superimposed on individual high-resolution T1-weighted magnetic resonance images (MRI). Phase lags between EMG and cerebral areas showing strongest coherence were determined by means of a Hilbert transform of both signals. In all patients, postural tremor was associated with strong coherence between tremor EMG and activity in contralateral primary sensorimotor cortex (S1/M1) at tremor or double tremor frequency. Phase lag values between S1/M1 activity and EMG revealed efferent and afferent components in the corticomuscular coupling. Taken together, our results indicate that postural tremor in WD is mediated through a pathological oscillatory drive from the primary motor cortex.

Synchronized brain network underlying postural tremor in Wilson's disease

“…Our current findings revealed a spatially distributed cerebello–thalamo–cortical network at tremor or double tremor frequency in WD postural tremor generation, including S1/M1, higher cortical motor areas (PM, SMA), PPC, and thalamus contralateral to the forearm tremor as well as ipsilateral cerebellum. We revealed coupling between S1/M1 and peripheral tremor in the first place,11 whereas the majority of other cerebral sources have not been consistently coherent with the tremor EMGs. Because of this lack of cerebro–muscular coherence, our CTC network findings cannot be explained by independent coupling of the different brain areas with the tremor EMGs.…”

“…In all patients, contralateral primary sensorimotor cortex demonstrated strongest cerebro–muscular coupling to right‐sided tremor EMG 11. The majority of other cerebral sources revealed no consistent significant cerebro–muscular coherence.…”

“…Five male WD patients (age, 33–54 years; mean, 40.2 years) participated in our study. Data of cortico–muscular coherence between S1/M1 and tremor EMGs in these patients have recently been published 11. On the day of MEG recordings, laboratory diagnostics including liver function tests and serum copper, serum ceruloplasmin, serum ammonia, 24‐hour urinary copper excretion, and a detailed neurological examination (H.H., A.S.) were performed on each participant.…”

“…First, tomographic maps of cerebro–muscular coherence were computed to identify the area of the strongest coherence to the EMG (Fig. 1, left) 11. Second, this source was defined as the reference region for further cerebro–cerebral coherence analysis within the entire brain (Fig.…”

Study on Lesion Assessment of Cerebello-Thalamo-Cortical Network in Wilson’s Disease with Diffusion Tensor Imaging

“…Is there any correlation between the abnormalities in diffusion images and the clinical symptoms? Magnetoencephalographic data of symptomatic patients of WD have been published and demonstrated involvement of a cerebello-thalamo-cortical network in WD tremor generation [6, 30]. Sudmeyer et al showed strongly significant correlation between unified Parkinson's disease rating scale part III action tremor score and MRI signal change ratio in the head of the caudate nucleus, the globus pallidus, and the substantia nigra in patients of WD [10].…”