Cerebello-thalamo-cortical network is intrinsically altered in essential tremor: evidence from a resting state functional MRI study.

Cerebello-thalamo-cortical network is suggested to be involved in the pathophysiology of Essential Tremor (ET). 23 patients with ET and 23 matched HC underwent a 3T-MRI with acquisition of a resting state sequence. Connectivity was investigated using a seed-based regression analyses approach. In ET patients were observed: Reduced connectivity between left primary motor cortex (M1) seed and right premotor cortex and cerebellum and bilateral premotor, parietal areas, supplementary motor area (SMA); Increased connectivity between left somatosensory cortex (S1) seed and parietal areas, M1, premotor cortex, SMA; reduced connectivity of this seed with cerebellum. Increased connectivity of SMA seed with premotor cortex and decreased with parietal and precentral areas; Increased connectivity between left thalamus seed and cerebellum; Reduced connectivity between right cerebellum seeds and other cerebellar areas, precentral and premotor areas. ET showed altered connectivity within the cortical sensory-motor network and between cerebral cortex and cerebellum. The increased connectivity between cerebellum and thalamus is consistent with their crucial role in tremor generation. These findings support the dynamical entrainment of multiple central oscillators throughout the cerebello-thalamo-cortical network in ET. This evidence is strengthened by the finding that this network is altered also when the core symptom is absent.

Morphometric and functional MRI changes in essential tremor with and without resting tremor.

The etiopathogenesis of essential tremor (ET) is still debated, since the predominant role of circuit dysfunction or brain degenerative changes has not been clearly established. The relationship with Parkinson's Disease (PD) is also controversial and resting tremor occurs in up to 20 % of ET. We investigated the morphological and functional changes associated with ET and we assessed potential differences related to the presence (ET+R) or absence (ET-R) of resting tremor. 32 ET patients (18 ET+R; 14 ET-R) and 12 healthy controls (HC) underwent 3T-MRI protocol including Spoiled Gradient T1-weighted sequence for Voxel-Based Morphometry (VBM) analysis and functional MRI during continuous writing of "8" with right dominant hand. VBM analysis revealed no gray and white matter atrophy comparing ET patients to HC and ET+R to ET-R patients. HC showed a higher BOLD response with respect to ET patients in cerebellum and other brain areas pertaining to cerebello-thalamo-cortical circuit. Between-group activation maps showed higher activation in precentral gyrus bilaterally, right superior and inferior frontal gyri, left postcentral gyrus, superior and inferior parietal gyri, mid temporal and supramarginal gyri, cerebellum and internal globus pallidus in ET-R compared to ET+R patients. Our findings support that the dysfunction of cerebello-thalamo-cortical network is associated with ET in absence of any morphometric changes. The dysfunction of GPi in ET+R patients, consistently with data reported in PD resting tremor, might suggest a potential role of this structure in this type of tremor.

Cataract surgery under topical anesthesia in a patient with Parkinson disease and deep brain stimulation: a report of feasibility.

PURPOSE: Deep brain stimulation provides benefits for people with Parkinson disease by managing some of their complications. None of the few reports in the current literature establishes the functionality of deep brain stimulation when activated during phacoemulsification. METHODS: A 70-year-old woman with subthalamic deep brain stimulator (DBS) for advanced Parkinson disease was referred to our center for cataract surgery. To evaluate any possible interference between ultrasounds and the DBS, we registered the impedance of the electrodes before and after surgery. RESULTS: The patient underwent uneventful phacoemulsification of her right eye under topical anesthesia with her internal pulse generator device activated. During the surgical procedure, all potential variations of the impedance of the electrodes were recorded. CONCLUSIONS: This report demonstrates that phacoemulsification under topical anesthesia is a feasible procedure in patients with DBS, showing no interference between the ultrasounds and the internal pulse generator.

Influences of dopaminergic treatment on motor cortex in Parkinson disease: a MRI/MRS study.

The objective of this study was to investigate neurochemical and metabolic changes in the motor cortex in a group of de novo Parkinson's disease (PD) patients before and after 6 mo treatment with the dopamine agonist pergolide. Proton magnetic resonance spectroscopy (1H-MRS) has been used to study striatal and cortical metabolism in PD and other parkinsonisms. So far, no studies evaluating possible brain metabolic changes in PD patients before and after dopaminergic therapy have been reported. De novo PD patients (11) and controls (11) underwent clinical evaluation (UPDRS-III motor evaluation) and a first single-voxel 1H-MRS of the motor cortex. 1H-MRS studies were performed using the PROBE-SV System implemented on a 1.5 Tesla Scanner (GE Medical System, Milwaukee, WI). Pergolide was administered up to a dose of 1 mg t.i.d. After 6 mo follow-up, all patients were clinically evaluated and a second single-voxel 1H-MRS was performed. Lower values of Cho/Cr and NAA/Cr ratios were observed in the motor cortex of PD patients compared with controls (P < 0.02 and P < 0.01, respectively). After 6 mo therapy with pergolide (1 mg t.i.d), PD patients showed an improvement in motor performances (P < 0.05) and an increase in Cho/Cr ratios in the motor cortex at the second 1H-MRS evaluation (P < 0.05) was reported. In conclusion, cortical NAA/Cr and Cho/Cr ratios may be impaired in de novo PD. Dopaminergic therapy capable of improving motor function may restore the Cho/Cr ratio in the motor cortex.