Denis Ducreux

Anatomical connections between brain areas activated during rectal distension in healthy volunteers: A visceral pain network

Diffusion Tensor Imaging (DTI) is a promising new imaging method allowing in vivo mapping of anatomical connections in the living human brain. We combined DTI with functional magnetic resonance imaging (fMRI) to investigate the anatomical relationships between areas involved in visceral sensations in humans.

Clinical, functional and structural determinants of central pain in syringomyelia

The present study aimed to investigate the relationship between neuropathic symptoms (i.e. pain and paraesthesia/dysaesthesia) and structural damage and functional alterations of spinal sensory tracts in patients with syringomyelia. Three-dimensional fibre tracking of the cervical spinal cord (at level C3-C4), electrophysiological assessments of nociceptive (laser-evoked potentials) and non-nociceptive (somatosensory-evoked potentials) pathways and quantitative sensory testing were carried out in 37 patients with syringomyelia, 27 with neuropathic pain and 21 controls. Four regions of the body (both hands and shoulders) were systematically examined with laser-evoked potentials and quantitative sensory testing, and somatosensory-evoked potentials were induced from both hands. The diffusion tensor imaging variables investigated included the mean fractional anisotropy, the mean apparent diffusion coefficient and the number of reconstructed nerve fibres of the tracts located within three volumes of interest (full spinal section, anterior cord and posterior cord). Consistent with the results of previous studies, patients with or without neuropathic pain were indistinguishable on the basis of quantitative sensory testing, laser-evoked and somatosensory-evoked potentials and three-dimensional fibre tracking analyses. However, in patients with neuropathic pain, higher average daily pain intensity was correlated with greater structural damage to the spinal cord, as assessed by fractional anisotropy (Spearmans ρu2009=u2009-0.64, Pu2009=u20090.020) and the number of reconstructed nerve fibres (ru2009=u2009-0.75; Pu2009=u20090.020) of the full spinal cord. The number of reconstructed nerve fibres was negatively correlated with two neuropathic dimensions, i.e. deep spontaneous pain (ru2009=u2009-0.59, Pu2009=u20090.040) and paraesthesia/dysaesthesia (i.e. pins and needles/tingling) (ru2009=u2009-0.67, Pu2009=u20090.020), suggesting that various pain descriptors have distinct underlying mechanisms. Patients with both spontaneous and evoked pain clearly differed from patients with spontaneous pain only. Patients with spontaneous pain only had more severe spinal cord damage, and the correlation between average daily pain intensity and fractional anisotropy of the full spinal cord was particularly strong in this subgroup of patients (Spearmans ρ = -0.93, Pu2009=u20090.008). By contrast, patients with both spontaneous and evoked pain had not only less structural spinal cord damage, but also better preserved spinothalamic and lemniscal tracts on quantitative sensory testing and electrophysiological testing. These data showed, for the first time, a direct relationship between central neuropathic pain and objective markers of spinal cord damage, and confirmed the clinical relevance of 3D fibre tracking for the sensory assessment of patients with a spinal cord lesion.

Assessment of spinal somatosensory systems with diffusion tensor imaging in syringomyelia

Objective: The use of diffusion tensor imaging with three-dimensional fibre tracking (DTI-FT) was tested for the assessment of spinal sensory tract lesions. The relationships between tract lesions quantified with DTI-FT were systematically examined, and somatosensory dysfunction was assessed with quantitative sensory testing (QST) and laser-evoked potentials (LEP), in patients with syringomyelia. Methods: 28 patients with cervical syringomyelia and thermosensory impairment of the hands, and 19 healthy volunteers, were studied. A DTI-FT of the spinal cord was performed, focusing on the upper segment (C3–C4) of the syrinx. Three-dimensional DTI-FT parameters (fractional anisotropy (FA) and apparent diffusion coefficient (ADC)) of the full, anterior and posterior spinal cord were individually compared with QST (thermal detection thresholds) and LEP (amplitude, latency and spinothalamic tract (STT) conduction time) of the hands. Results: Patients had a significantly lower FA, but not ADC, than healthy subjects. The mean FA of the full section of the spinal cord was correlated both to sensory deficits (ie, increase in warm (rhou200a=u200a−0.63, p<0.010) and cold thresholds (rhou200a=u200a−0.72; p<0.001 of the hands)) and to changes in LEP parameters, in particular STT conduction time (rhou200a=u200a−0.75; p<0.010). Correlations between FA and the clinical and electrophysiological measures were higher in the anterior area (where the spinothalamic tracts are located) than in the posterior area of the spinal cord. Conclusions: The data indicate that diffusion tensor imaging with 3D-fibre tracking is a new imaging method suitable for the objective and quantitative anatomical assessment of spinal somatosensory system dysfunction.

Hematological disorders related cerebral infarctions are mostly multifocal.

Hematological disorders (HD) have been estimated to implicate approximately 1% of patients with arterial ischemic stroke. However, previously published studies are mostly retrospective or based on case reports or small series in selected young patients. We herein prospectively included consecutive patients with MRI-confirmed cerebral arterial infarctions among individuals admitted in our stroke unit during a 32 month period to determine the clinical and neuroradiological features of ischemic stroke due to HD. Patients with both HD and other identified sources of stroke were excluded. Among patients who were admitted for suspected stroke, 590 had diffusion-weighted MRI confirmed acute arterial infarcts. Cause of the cerebral infarction was HD in 13 patients (2.2%): myeloproliferative disorders (n=4), multiple myeloma (1), lymphoma (1), chronic lymphocytic leukemia (1), disseminated intravascular coagulation (2), thrombotic thrombocytopenic purpura (1), antiphospholipid antibody syndrome (2) and homozygous Q506 factor V mutation associated with lupus anticoagulant (1). The HD were previously known in 6 patients. The only significant difference between the groups of patients with or without HD was the prevalence of multiple acute infarcts in different vascular territories, detected in 53.8% of patients with HD versus 7.8% of patients without HD (mostly due to atherosclerosis, small vessel disease or cardioembolism) (p<0.0001; Fisher exact test). Initial treatment in stroke unit included anticoagulation, steroids, chemotherapy, phlebotomy or plasmatic exchanges, according to etiology. Rankin score at six months was ≤2 in 8 patients. A large spectrum of hematological diseases can be associated with cerebral infarction. In the etiologic work up, HD should be particularly looked for in patients with multifocal acute infarcts to adapt specific therapeutic management.

131 RELATIONSHIP BETWEEN STRUCTURAL LESION OF SPINAL SENSORY TRACTS AND NEUROPATHIC PAIN IN SYRINGOMYELIA PATIENTS

Background & Aims: Pain is the most prominent but least well-studied feature of osteoarthritis (OA). Retrograde labelling of neurons innervating the OA joint decreases 40% at 31 days of disease progression, with the total number of DRG cells remaining unaltered, but increasing the number of medium-large cells. Therefore, we hypothesized that neuronal damage might be occurring during OA, and to test this hypothesis we evaluated the expression of ATF-3 and NPY (known to be increased by neuronal damage) in DRG neurons. Since ATF-3 has also been associated with the regeneration of injured cells, we also evaluated its colocalization with the regeneration marker GAP-43. Methods: All procedures were performed according to the ethical guidelines for the study of experimental pain in conscious animals. OA was induced by injection of 2mg of mono-iodoacetate in the knee joint of adult Wistar rats. Animals were sacrificed at 3, 7 and 14 days post-injection. L3-L5 DRGs were used for immunohistochemistry for NPY, ATF-3 and GAP-43. Results: An increase in the number of ATF-3-positive cells was observed 3 days after the induction of OA. Such increase diminished over time, but the percentage of ATF-3 cells positive for GAP43 increased at days 7 and 14. NPY expression showed a similar pattern as ATF-3 expression. Conclusion: The increased ATF-3 and NPY expression suggests that damage in DRG neurons innervating the OA joint may be occurring. The increased co-localization of ATF-3 and GAP-43 over time indicates that neuronal regeneration may be taking place as a response to neuronal damage.