Table 2.

Cerebellar physiological studies for tremor

Authors and year	Techniques	Clinical syndrome	Number of patients	Number of controls	Methods	Findings/outcome
Muthuraman et al. [53]	EEG	ET	20	10	Coherence, source localization-DICS, connectivity-RPDC	Oscillating cerebral networks underlying classical ET and aging-related tremor differ, suggests a pathophysiological difference
Schnitzler et al. [54]	MEG, EMG	ET	8	-	Source localization- DICS, Partial coherence	Network of brain areas including the cerebellum shows oscillatory interactions, leading to a rhythmic modulation of muscle activity becoming apparent as tremor
Timmermann et al. [55]	MEG, EMG	PD resting tremor	6	-	Source localization- DICS, coherence	Tremor-related oscillatory activity within a cerebral network, with abnormal coupling in a cerebello-diencephalic cortical loop and cortical motor and sensory areas contralateral to the tremor hand
Pollock et al. [56]	MEG, EMG	PD	10	11	Source localization- DICS, coherence	Decreases in cerebro-cerebral coupling between thalamus and motor cortical areas after levodopa intake. Tremor oscillatory networks consists of sources in contralateral primary sensorimotor cortex, supplementary motor area, contralateral premotor cortex, thalamus, secondary somatosensory cortex, posterior parietal cortex and ipsilateral cerebellum
Muthuraman et al. [58]	EEG-EMG	ET, PD	ET-34, PD-34	34	Coherence, Source localization- DICS, connectivity-TPDC	Differing topography of cerebellar activity in PD, ET and mimicked tremor
Pedrosa et al. [59]	EEG, MRI	ET	20	20	Source localization- DICS	Increases within frontal motor activity are associated with tremor emergence, and tremor amplitude reduction is linked to changes in cerebellar activity
Muthuraman et al. [57]	EEG, EMG	PD, ET	PD-10, ET-10	10	Source localization- DICS, RPDC	Voluntary tremor has a unidirectional flow from the diencephalon to cortex. Explanations about pathological and voluntary tremors having similar neuronal pathways, but pathologic tremors are unable to be controlled voluntarily. Cerebellar source found in ET, PD patients and healthy subjects
Muthuraman et al. [60]	EEG, EMG	Orthostatic tremor	15	-	Source localization- DICS, coherence	Initial bilateral corticomuscular coherence pattern in orthostatic tremor, followed by a segregated unilateral pattern. Standing tremor frequency consists of sources in the primary motor leg area, supplementary motor area, primary sensory cortex, prefrontal/premotor cortex, thalamus, and cerebellum
Südmeyer et al. [61]	MEG, EMG	Postural tremor-WD	5	-	Source localization- DICS, coherence	Synchronized network consisting of the cerebello–thalamo–cortical network, involving primary sensorimotor cortex, supplementary motor area, premotor cortex, and posterior parietal cortex generates WD postural tremor
Pan et al. [62]	Cb-EEG	ET	20	20	In vivo analysis, Time frequency analysis	Excessive cerebellar oscillations in patients with ET
Wong et al. [67]	Cb-EEG	Familial ET, Sporadic ET	Familial-22, Sporadic-18	20	Spectral analysis	In Familial ET cerebellar oscillations are associated with tremor severity but not sporadic ET. Conserved cerebellar oscillations in familial and sporadic ET patients
Bosch et al. [68]	EEG	PD	75	39	Spectral analysis	Resting state, theta band (4–7 Hz) cerebellar oscillations are abnormal
Bosch et al. [69]	EEG	PD	10 PD- with PI, 11 PD- without PI	15	Spectral analysis	Association of mid-frontal and mid cerebellar regions in postural stability and theta frequency oscillations (4–7 Hz) are important for postural control in PD
Bosch et al. [70]	EEG	PD	79	37	Time frequency analysis, connectivity analysis	Altered cerebellar oscillations in motor and cognitive task performances in PD

EEG electroencephalography, MEG magnetoencephalography, EMG electromyogram, Cb-EEG cerebellar EEG, MRI magnetic resonance imaging, ET essential tremor, PD Parkinson’s disease, WD Wilson’s disease, DICS dynamic imaging of coherent sources, TPDC temporal partial directed coherence, RPDC renormalized partial directed coherence, PI postural instability