Clinical contribution of PET neurotransmission imaging in neurological disorders

in Acta Neurologica Belgica (2005), 105(3), 119-136

Imaging neurotransmission in vivo using positron emission tomography (PET) is a rapidly expanding clinical science. The present review summarizes the actual contribution of PET imaging to clinical ... [more ▼]

Imaging neurotransmission in vivo using positron emission tomography (PET) is a rapidly expanding clinical science. The present review summarizes the actual contribution of PET imaging to clinical problems in movement and seizure disorders and dementia. [less ▲]

CASL fMRI of subcortico-cortical perfusion changes during memory-guided finger sequences

in Neuroimage (2005), 25(1), 122-132

Arterial spin labeling (ASL) perfusion functional magnetic resonance imaging (fMRI) is an attractive alternative to BOLD fMRI. Nevertheless, current ASL fMRI techniques are limited by several factors that ... [more ▼]

Arterial spin labeling (ASL) perfusion functional magnetic resonance imaging (fMRI) is an attractive alternative to BOLD fMRI. Nevertheless, current ASL fMRI techniques are limited by several factors that hamper more routine applications in humans. One of these factors is restricted brain coverage so that whole-brain ASL fMRI studies have never been reported. The present study tested the ability of a multislice continuous ASL (CASL) fMRI approach using a small surface coil placed on the subject's neck to map changes in regional cerebral blood flow (rCBF) throughout the brain while healthy individuals (N = 15) performed memory-guided sequential finger movements at a mean rate of similar to0.5 Hz. As predicted by results from a large number of studies, reliable task-related increases in flow were detected across subjects not only in primary and associative cortical areas but also in subcortical brain regions. When normalized to baseline, rCBF increased 31% in the hand representation area (HRA) of left primary motor cortex (M1) 13% in the left supplementary motor area proper (SMA), 10% in the left dorsolateral prefrontal cortex (DLPFC), 10-18% in the bilateral intraparietal sulci, 6% in the HRA of left putamen, 10% in the left thalamus, and 17% in the right anterior cerebellum. In addition to these increases, 6% and 4% decreases in rCBF were detected in the HRA of the right M1 and the bilateral posterior cingulate sulci, respectively. These results demonstrate that perfusion-based fMRI using CASL with a separate labeling coil can now be used to characterize task-related flow changes in most of the brain volume with adequate accuracy and sensitivity. [less ▲]

Time-of-day modulations of rCBF response in functional brain imaging studies: a meta-analysis

in NeuroImage (2005), 26(Suppl. 1),

Changes in brain anatomy in focal hand dystonia

in Annals of Neurology (2004), 55(5), 736-739

No consistent cerebral anatomical abnormality has ever been reported in primary focal hand dystonia (FHD). The present voxel-based morphometry study showed a significant bilateral increase in gray matter ... [more ▼]

No consistent cerebral anatomical abnormality has ever been reported in primary focal hand dystonia (FHD). The present voxel-based morphometry study showed a significant bilateral increase in gray matter in the hand representation area of primary somatosensory and, to a lesser extent, primary motor cortices in 36 patients with unilateral FHD compared with 36 controls. The presence of anatomical changes in the perirolandic cortex for the unaffected hand as well as that for the affected hand suggests that these disturbances may be, at least in part, primary. [less ▲]

Low-frequency coherent fluctuations in BOLD activity: a preliminary report

Poster (2004)

Background Low frequency (<0.1Hz) fluctuations originating from blood flow and oxygenation have been observed in the brain by different groups (Golanov et al. 1994; Biswal.et al. 1995). The goal of this ... [more ▼]

Background Low frequency (<0.1Hz) fluctuations originating from blood flow and oxygenation have been observed in the brain by different groups (Golanov et al. 1994; Biswal.et al. 1995). The goal of this study was to use BOLD fMRI to characterize coherent fluctuations in those low frequencies between spatially distant brain regions. Methods Thirteen right-handed subjects were studied using blocked-design BOLD fMRI at rest and as they performed sequential finger movements at a slow rate (~0.5 Hz) with their right hand. Serial acquisitions of EPI images were obtained at 3T using a single-shot 2D gradient-echo echo-planar imaging sequence. Data were processed and analyzed using standard procedures implemented in the statistical parametric mapping software (SPM2). Temporal profile of brain activity in 6 predefined regions (left S1M1, right S1M1, SMA, left thalamus, right cerebellum and CSF) were extracted on a subject-by-subject basis using the VOI tool in SPM2. After deconvolution (Gitelman et al. 2003), time series data representing movement and resting conditions were concatenated to create 2 within-condition time-series. After subtracting the mean over all epochs from each epoch, the (complex) coherency was calculated in the 5 lowest frequency bins with a frequency resolution of 1/17.5Hz (0, 0.05, 0.11, 0.17, 0.23 Hz). Real and imaginary parts of coherency, representing correlation and correlation of phase-shifted signals, respectively, were analyzed separately. Coherency was computed independently for each region pairs and each subject. Significance was defined as p<0.05 Bonferroni corrected for multiple comparisons. Results The main finding was the presence of coherent fluctuations in BOLD signal mainly in the lowest frequencies for (almost) all regions. The real part of coherency was equally pronounced during the movement and rest conditions. The only exception was a larger coherence during rest than during the task condition in the lowest frequencies between left and right S1M1. We could not find any significant imaginary part of coherency indicating that the time delays between dependent neural activations are negligible compared to the inverse frequencies under study. Partialling out the data in any of the regions did not have any significant impact on coherence map. Importantly, there was no evidence of coherent activity between any of the brain regions and CSF in any of the frequency bands. Discussion BOLD signal recorded during different behavioral steady-states showed very similar coherent fluctuations for all regions pairs studied mainly in the lowest frequencies. Those results are in good agreement with electrophysiological recordings in monkeys in which high coherence in band-limited power of local field potential signals have been reported at very low frequencies (<0.1Hz) (Leopold et al. 2003). In that study, coherence patterns were also highly similar under distinctly different behavioral states. Task-independent coherence in lower frequencies may be related to whole brain slow synchronous oscillations whose significance remains to be elucidated. References Golanov et al. (1994). Am J Physiol. 266; R204-214. Biswal et al. (1995). Magn Reson Med. 34; 537-541. Gitelman et al. (2003). NeuroImage. 19; 200-207. Leopold. et al. (2003). Cereb Cortex. 13; 422-433. [less ▲]

Exercise-induced dystonia as a preceding symptom of familial Parkinson's disease

in Movement Disorders (2004), 19(2), 228-230

Paroxysmal exercise-induced dystonia can occur with Parkinson's disease (PD), and in rare cases, this can also be the presenting symptom. We report on 2 second cousins (no known consanguinity) who ... [more ▼]

Paroxysmal exercise-induced dystonia can occur with Parkinson's disease (PD), and in rare cases, this can also be the presenting symptom. We report on 2 second cousins (no known consanguinity) who presented with paroxysmal exercise-induced dystonia who later developed clinical features of PD. Although autosomal recessive inheritance was suggested, and the dystonic features further suggest parkin as a possible cause, ssequencing for parkin mutations was negative and this family may represent a genetic variant of PD. Further genotype-phenotype studies in this and similar families may give clues to pre-symptomatic symptoms in PD and may reflect a particular phenotype of interest for genetics studies in the future. [less ▲]

Neural and cognitive bases of upper limb apraxia in corticobasal degeneration

in Neurology (2001), 57(7), 1259-1268

OBJECTIVE: To investigate the neural and cognitive bases of upper limb apraxia in corticobasal degeneration (CBD). METHODS: Eighteen patients with CBD underwent a cognitive neuropsychological assessment ... [more ▼]

OBJECTIVE: To investigate the neural and cognitive bases of upper limb apraxia in corticobasal degeneration (CBD). METHODS: Eighteen patients with CBD underwent a cognitive neuropsychological assessment of apraxia and resting [(18)F]-fluorodeoxyglucose PET scanning. Two complementary measures of apraxia were computed for each modality of gesture production. First, a performance score measured error frequency during gesture execution. Second, as a more stringent test of the integrity of the praxis system, the correction score measured the patient's ability to correct his or her errors on a second attempt. For each measure type, a cut-off score for the presence of apraxia was defined with regard to healthy controls. Using each cut-off score, the regional cerebral glucose metabolism of patients with CBD with apraxia (i.e., performing below cut-off score) was compared with that of patients with CBD without apraxia. RESULTS: Mean performance scores were below normal values in all modalities. Anterior cingulate hypometabolism predominated in patients with CBD who performed below the cut-off performance score. At variance, mean correction scores were below normal values for gesture imitation only. Hypometabolism in superior parietal lobule and supplementary motor area characterized patients with CBD who were unable to correct their errors at the same rate as control subjects did. CONCLUSIONS: Distinct neural networks underlie distinct aspects of the upper limb apraxic deficits in CBD. Extending previous findings of gesture production deficits in CBD, the use of complementary measures of apraxic behavior discloses a visuoimitative upper limb apraxia in CBD, underlain by a metabolic decrease in a parietofrontal neural network. [less ▲]

Voxel-based distribution of metabolic impairment in corticobasal degeneration

in Movement Disorders (2000), 15(5), 894-904

This report emphasizes the precise topographic distribution of cerebral metabolic impairment in corticobasal degeneration (CBD) and the pathophysiological differences between CBD and progressive ... [more ▼]

This report emphasizes the precise topographic distribution of cerebral metabolic impairment in corticobasal degeneration (CBD) and the pathophysiological differences between CBD and progressive supranuclear palsy (PSP). Statistical parametric mapping (SPM96) analysis of 18FDG positron emission tomography (PET) data was performed in 22 patients with CBD compared with 46 healthy subjects (HS) and 21 patients with PSP who were studied at rest. A statistical threshold of p <0.001 was fixed, further corrected for multiple or independent comparisons (p <0.05). In comparison with HS, the metabolic impairment in CBD was asymmetrically distributed in the putamen, thalamus, precentral (Brodmann's area, BA 4), lateral premotor (BA 6/44) and supplementary motor areas (SMA, BA 6), dorsolateral prefrontal (8/9/46) cortex, and the anterior part of the inferior parietal lobe (BA 40) including the intraparietal sulcus (BA 7/40). A similar hypometabolic pattern was observed for most individual analyses. When PSP was compared with CBD, metabolic impairment predominated in the midbrain, anterior cingulate (BA 24/32), and orbitofrontal regions (BA 10). The reverse contrast showed more posterior involvement in CBD (BA 6 and 5/7/40) including SMA. Our data suggest that multiple components of neural networks related to both movement execution and production of skilled movements are functionally disturbed in CBD compared with both HS and PSP. [less ▲]

Medial temporal lobe metabolic impairment in dementia associated with motor neuron disease

in Journal of the Neurological Sciences (1999), 168(2), 145-150

In the course of their disease certain patients with frontotemporal dementia (FTD) develop clinical features compatible with a motor neuron disease (FTD-MND). Previous reports have suggested that the ... [more ▼]

In the course of their disease certain patients with frontotemporal dementia (FTD) develop clinical features compatible with a motor neuron disease (FTD-MND). Previous reports have suggested that the functional pattern is similar in FTD and FTD-MND. However, some neuropathological studies suggest greater involvement of medial temporal regions in FTD-MND than in FTD. Using statistical parametric mapping (SPM96), we compared the metabolic patterns obtained at rest with positron emission tomography in 10 FTD patients and three FTD-MND patients with those obtained from 46 healthy subjects (HS). Mean age, duration of illness and dementia stage did not differ statistically between the FTD and FTD-MND groups. In comparison with HS, both groups showed frontal and anterior temporal hypometabolism at P<0.001. When the FTD-MND group was compared to the FTD group, significant hypometabolism was only observed in bilateral amygdala, bilateral hippocampus, and bilateral enthorinal and parahippocampal regions (Brodmann's areas, BA 28/36) at P<0.005. We found no significant differences in regional glucose uptake when FTD patients were contrasted to FTD-MND patients. Our results suggest statistically comparable frontal and lateral temporal hypometabolism in both conditions but greater impairment of medial temporal lobe activity in FTD-MND. Our results and a review of the literature support the hypothesis that there is a functional continuum between classical motor neuron disease (cMND), FTD-MND, and FTD. [less ▲]

Occulo-pharyngeal muscular distrophy : a case report

Conference (1999)