Giuseppe Nicoletti

Monoamine Oxidase-A Genetic Variations Influence Brain Activity Associated with Inhibitory Control: New Insight into the Neural Correlates of Impulsivity

BACKGROUND Previous evidence has shown that genetic variations in the serotonergic system contribute to individual differences in personality traits germane to impulse control. The monoamine oxidase-A (MAO-A) gene, coding for an enzyme primarily involved in serotonin and noradrenaline catabolism, presents a well-characterized functional polymorphism consisting of a variable number of tandem repeats in the promoter region, with high-activity and low-activity variants. High-activity allele carriers have higher enzyme expression, lower amine concentration, and present higher scores on behavioral measures of impulsivity than low-activity allele carriers. METHODS We studied the relationship of this polymorphism to brain activity elicited by a response inhibition task (Go/NoGo task), using blood oxygenation level-dependent (BOLD) functional magnetic resonance imaging in 24 healthy men. RESULTS Direct comparison between groups revealed a greater BOLD response in the right ventrolateral prefrontal cortex (Brodmanns area [BA] 45/47) in high-activity allele carriers, whereas a greater response in the right superior parietal cortex (BA 7) and bilateral extrastriate cortex (BA 18) was found in low-activity allele carriers. CONCLUSIONS These data suggest that a specific genetic variation involving serotonergic catabolism can modulate BOLD response associated with human impulsivity.

Essential Head Tremor Is Associated with Cerebellar Vermis Atrophy: A Volumetric and Voxel-Based Morphometry MR Imaging Study

BACKGROUND AND PURPOSE: Our aim was to investigate the presence of brain gray matter (GM) abnormalities in patients with different forms of essential tremor (ET). MATERIALS AND METHODS: We used optimized voxel-based morphometry (VBM) and manually traced single region-of-interest analysis in 50 patients with familial ET and in 32 healthy subjects. Thirty patients with ET had tremor of the arms (a-ET), whereas the remaining 20 patients had both arm and head tremor (h-ET). RESULTS: VBM showed marked atrophy of the cerebellar vermis in the patients with h-ET with respect to healthy subjects (Pcorrected < .001). Patients with a-ET showed a trend toward a vermal GM volume loss that did not reach a significant difference with respect to healthy controls (Puncorrected < .01). The region-of-interest analysis showed a reduction of the cerebellar volume (CV) in the h-ET group (98.2 ± 13.6 mm3) compared with healthy controls (110.5 ± 15.5 mm3, P < .012) as well as in the entire vermal area (790.3 ± 94.5 mm2, 898.6 ± 170.6 mm2, P < .04 in h-ET and control groups, respectively). CONCLUSIONS: Atrophy of the cerebellar vermis detected in patients with h-ET strongly supports the evidence for the involvement of the cerebellum in the pathophysiology of ET. The lack of a significant CV loss observed in patients with a-ET suggests that a-ET and h-ET might represent distinct subtypes of the same disease.

Diffusion tensor MRI changes in cerebellar structures of patients with familial essential tremor

Objective: The aim of our study was to investigate the microstructural integrity of brain regions functionally involved in the tremor loop in patients with familial essential tremor (FET), using diffusion tensor imaging (DTI). Methods: Twenty-five patients with FET, 15 patients with Parkinson disease (PD), and 15 healthy subjects were studied. DTI was performed to measure fractional anisotropy (FA) and mean diffusivity (MD) in various regions of interest: red nucleus, dentate nucleus (DN), cerebellar white matter, middle (MCP) and superior cerebellar peduncle (SCP), and ventrolateral thalamus. Results: In patients with FET, FA values in the DN (median 0.19, range 0.13–0.23) were reduced (p < 0.001) compared with patients with PD (median 0.37, range 0.32–0.58) and healthy controls (median 0.36, range 0.33–0.40). In patients with FET, FA was also reduced (p = 0.003) and MD values increased (p < 0.001) in the SCP compared with patients with PD and healthy controls. Among patients with FET, those with longer disease duration showed FA values in the DN lower than those with shorter disease duration (p = 0.018). Patients with FET could be completely distinguished from both patient with PD and healthy controls using FA values of the DN alone. Conclusion: Neuroimaging evidence of microstructural changes consistent with neurodegeneration was found in the dentate nucleus (DN) and SCP of patients with familial essential tremor. This suggests that neurodegenerative pathology of cerebellar structures may play a role in essential tremor. Further studies are needed to assess the role of fractional anisotropy and mean diffusivity changes in DN and SCP in the differential diagnosis of essential tremor and Parkinson disease, which may present similar clinical signs at the onset of disease.

Patterns of brain atrophy in Parkinson’s disease, progressive supranuclear palsy and multiple system atrophy

BACKGROUND AND PURPOSE Quantitative analysis of brain atrophy may be useful in differentiating Parkinsons Disease (PD) from Progressive Supranuclear Palsy (PSP) and parkinsonian variant of Multiple System Atrophy (MSA-P); the aim of this study was to identify the volumetric differences of subcortical structures in patients with PD, PSP and MSA-P using a novel and validated fully-automated whole brain segmentation method. METHODS Volumetric MRIs were obtained in 72 patients with PD, 32 patients with PSP, 15 patients with MSA-P, and in 46 control subjects. Subcortical volume was measured automatically by FreeSurfer. Multivariate analysis of covariance, adjusted for intracranial volume (ICV), sex and age, was used to explore group differences. RESULTS No volumetric differences were found between PD and controls group; otherwise the volumes of the cerebellum, the thalamus, the putamen, the pallidum, the hippocampus, and the brainstem were significantly reduced in PSP and MSA-P compared to patients with PD and control subjects. PSP and MSA-P patients only differed in thalamus volume which was smaller in PSP group (p < 0.001). Moreover, patients with PSP and MSA-P showed a ventricular system (including lateral, third and fourth ventricles) larger than that detected in PD and controls (p < 0.001). CONCLUSIONS Volumetric data obtained with automated segmentation of cerebral regions show a significant atrophy of different brain structures in parkinsonisms rather than in PD. Our study also demonstrates that the atrophy of the thalamus only occurs in PSP while the enlargement of the whole ventricular system characterizes both PSP and MSA-P.

Dopamine D2 receptor gene polymorphism and the risk of levodopa-induced dyskinesias in PD.

OBJECTIVE To investigate whether polymorphisms in the genes for dopamine receptors D1 and D2 are associated with the risk of developing peak-dose dyskinesias in PD. BACKGROUND Peak-dose dyskinesias are the most common side effects of levodopa therapy for PD. The identified predictors may only partially account for the risk of developing peak-dose dyskinesias because a substantial proportion of patients never develop peak-dose dyskinesias. Genetic factors could play a role in determining the occurrence of peak-dose dyskinesias. METHODS A case-control study of 136 subjects with sporadic PD and 224 population control subjects. We studied three polymorphisms involving the dopamine receptor D1 gene and one intronic short tandem repeat polymorphism of the dopamine receptor D2 gene. RESULTS The polymorphisms of the dopamine receptor D1 gene were not associated with the risk of developing PD or peak-dose dyskinesias. The 15 allele of the polymorphism of the dopamine receptor D2 gene was more frequent in parkinsonian subjects than in control subjects. More important, the frequency of both the 13 allele and the 14 allele of the dopamine receptor D2 gene polymorphism was higher in nondyskinetic than in the dyskinetic PD subjects. The risk reduction of developing peak-dose dyskinesias for PD subjects carrying at least 1 of the 13 or 14 alleles was 72% with respect to the PD subjects who did not carry these alleles. CONCLUSIONS Certain alleles of the short tandem repeat polymorphism of the dopamine receptor D2 gene reduce the risk of developing peak-dose dyskinesias and could contribute to varying susceptibility to develop peak-dose dyskinesias during levodopa therapy.

Cerebellar Atrophy in Essential Tremor Using an Automated Segmentation Method

BACKGROUND AND PURPOSE: Essential tremor (ET) is a slowly progressive disorder characterized by postural and kinetic tremors most commonly affecting the forearms and hands. Several lines of evidence from physiologic and neuroimaging studies point toward a major role of the cerebellum in this disease. Recently, voxel-based morphometry (VBM) has been proposed to quantify cerebellar atrophy in ET. However, VBM was not originally designed to study subcortical structures, and the complicated anatomy of the cerebellum may hamper the automatic processing of VBM. The aim of this study was to determine the efficacy and utility of using automated subcortical segmentation to identify atrophy of the cerebellum and other subcortical structures in patients with ET. MATERIALS AND METHODS: We used a recently developed automated volumetric method (FreeSurfer) to quantify subcortical atrophy in ET by comparing results obtained with this method with those provided by previous evidence. The study included T1-weighted MR images of 46 patients with ET grouped into those having arm ET (n = 27, a-ET) or head ET (n = 19, h-ET) and 28 healthy controls. RESULTS: Results revealed the expected reduction of cerebellar volume in patients with h-ET with respect to healthy controls after controlling for intracranial volume. No significant difference was detected in any other subcortical area. CONCLUSIONS: Volumetric data obtained with automated segmentation of subcortical and cerebellar structures approximate data from a previous study based on VBM. The current findings extend the literature by providing initial validation for using fully automated segmentation to derive cerebellar volumetric information from patients with ET.

Apparent diffusion coefficient of the superior cerebellar peduncle differentiates progressive supranuclear palsy from Parkinson's disease

The early diagnosis of progressive supranuclear palsy (PSP) may be challenging, because of clinical overlapping features with Parkinsons disease (PD) and other parkinsonian syndromes such as the Parkinsonian variant of multiple system atrophy (MSA‐P). Conventional MRI can help in differentiating parkinsonian disorders but its diagnostic accuracy is still unsatisfactory. On the basis of the pathological demonstration of superior cerebellar peduncle (SCP) atrophy in patients with PSP, we assessed the SCP apparent diffusion coefficient (ADC) values in patients with PSP, PD, and MSA‐P in order to evaluate its differential diagnostic value in vivo. Twenty‐eight patients with PSP (14 with possible‐PSP and 14 with probable‐PSP), 15 PD, 15 MSA‐P, and 16 healthy subjects were studied by using diffusion weighted imaging (DWI). ADC was calculated in regions of interest defined in the left and right SCP by two clinically blinded operators. Intrarater (r = 0.98, P < 0.001) and interrater reliability (r = 0.97; P < 0.001) for SCP measurements were high. Patients with PSP had higher SCP rADC values (median 0.98 × 10−3mm2/s) than patients with PD (median 0.79 × 10−3 mm2/s, P < 0.001), MSA‐P (median 0.79 × 10−3 mm2/s, P < 0.001), and healthy controls (median 0.80 × 10−3 mm2/s, P < 0.001). DWI discriminated patients with PSP from PD and healthy subjects on the basis of SCP rADC individual values (100% sensitivity and specificity) and from patients with MSA‐P (96.4% sensitivity and 93.3% specificity). The higher values of rADC in SCP of patients with PSP correspond with the in vivo microstructural feature of atrophy detected postmortem and provide an additional support for early discrimination between PSP and other neurodegenerative parkinsonisms.

Glucocerebrosidase gene mutations are associated with Parkinson's disease in southern Italy.

Recent studies have reported an association between the glucocerebrosidase (GBA) gene and Parkinsons disease (PD). To elucidate the role of this gene in our population, we screened 395 PD patients and 483 controls from southern Italy for the N370S and the L444P mutations. We found 11 patients (2.8%) carrying a heterozygous mutant GBA allele, whereas only one control subject (0.2%) had a heterozygous substitution (P = 0.0018). These results strongly suggest that Italian carriers of a GBA mutation have an increased risk of developing PD.

Myocardial 123metaiodobenzylguanidine uptake in genetic Parkinson's disease

Myocardial 123Metaiodobenzylguanidine (MIBG) enables the assessment of postganglionic sympathetic cardiac innervation. MIBG uptake is decreased in nearly all patients with Parkinsons disease (PD). Our objective was to evaluate MIBG uptake in patients with genetic PD. We investigated MIBG uptake in 14 patients with PD associated with mutations in different genes (Parkin, DJ‐1, PINK1, and leucine‐rich repeat kinase 2 ‐LRRK2), in 15 patients with idiopathic PD, and 10 control subjects. The myocardial MIGB uptake was preserved in 3 of the 4 Parkin‐associated Parkinsonisms, in 1 of the 2 patients with DJ‐1 mutations, in 1 of the 2 brothers with PINK1 mutations, in 3 of the 6 unrelated patients with Gly2019Ser mutation in the LRRK2 gene, whereas it was impaired in all patients with idiopathic PD. MIBG was preserved in all control subjects. Our study shows that myocardial MIGB uptake was normal in 8 of 14 patients with genetic PD, suggesting that cardiac sympathetic denervation occurs less frequently in genetic PD than in idiopathic PD. Our findings also demonstrate that MIGB uptake has a heterogeneous pattern in genetic PD, because it was differently impaired in patients with different mutations in the same gene or with the same gene mutation.

Comparison of different MR venography techniques for detecting transverse sinus stenosis in idiopathic intracranial hypertension

AbstractCerebral venous outflow abnormalities, as transverse sinuses (TSs) stenosis,may underlie a picture of idiopathic intracranial hypertension (IIH). To identify the best non–invasive MR venography (MRV) technique for exploring the disturbance of flow of TSs in IIH patients, we compared threedimensional phase contrast (3–DPC) MRV images, acquired with different velocity encodings (15 and 40 cm/s) with two–dimensional time–of–flight (2D–TOF) MR images in 6 subjects with IIH and 12 age–matched normal controls. In both groups, we also measured flow velocity in TSs by using single slice 2D–CINE PC acquisitions. In all subjects with IIH, 3D-PC showed marked flow disturbance in the mid–lateral portion of both TSs when velocity encoding (VENC) was set to 15 cm/s while only a slightly irregular flow in TSs was detected when VENC was set to 40 cm/s or when 2D–TOF was used. By contrast, 3D–PC (VENC 15 and 40) and 2D–TOF techniques were comparable in detecting TS signal flow in normal controls. Measures of flow velocity, by using 2D-CINE PC, revealed a three–fold increase of velocity at the level of the flow disturbance in IIH patients compared to normal controls (p < 0.0001), suggesting a marked stenosis of mid–lateral portion of TSs in these patients. Setting the VENC to 15 cm/s on 3D–PC MRV may represent the best technical approach for visualizing disturbances of flow in TSs in subjects with symptoms suggestive of IIH.