Biomedical subjects

Denis Ducreux

Publications and source records attributed to Denis Ducreux.

8 recordsLinked to original sources

PubMed2006

Mechanisms of central neuropathic pain: a combined psychophysical and fMRI study in syringomyelia.

The pathophysiology of central pain syndromes is still poorly understood and their treatment remains a major challenge. It has long been suggested that lesions of the spinothalamic pathways are necessary for developing these pain syndromes. The recently proposed thermosensory disinhibition theory suggests that reduction of the inhibition of thermal sensory afferents that affect nociceptive systems may play a major pathophysiological role. Syringomyelia, which is frequently associated with central neuropathic pain, is characterized by a selective or preferential lesion of the spinothalamic tract resulting in thermosensory deficits of various extents and magnitudes. Thus, syringomyelia represents a unique 'pathological model' particularly suited to investigating the relationship between spinothalamic tract dysfunction, thermosensory deficits and pain. Here, we systematically compared the sensory loss (thermal and mechanical), using quantitative sensory testing, between 46 consecutive syringomyelia patients with or without neuropathic pain. We then further investigated the mechanisms of evoked pains in these patients, using functional MRI (fMRI) in a subgroup of patients with cold or brush-evoked allodynia, compared with patients without pain and healthy volunteers. We found no significant difference in the magnitude or extent of sensory deficits between patients with or without neuropathic pain, suggesting that lesions of the spinothalamic pathways are not sufficient for developing central pain. However, a different pattern of sensory deficits was observed between patients with spontaneous pain only (n = 11) and patients with both spontaneous pain and allodynia (n = 20), suggesting that the mechanisms of central pain are not univocal. In patients with spontaneous pain only, the thermal sensory loss was significantly more asymmetrical and there was a direct relationship between the extent of thermosensory deficits (i.e. deafferentation) and the intensity of burning pain. In contrast, patients with allodynia had reduced thermal deficits, in terms of both magnitude and extent. In addition, the sensory deficits were different between patients with cold or tactile allodynia, suggesting distinct pathophysiological mechanisms related to the sub-modalities of allodynia. Our fMRI study further confirmed this, showing that different sub-types of allodynia were associated with distinct patterns of brain activity, which do not necessarily correspond to the 'pain matrix' involved in acute physiological pain. The prefrontal cortex was the only area consistently activated by pathological evoked pains, suggesting that alteration of high-level pain modulatory mechanisms might play a major role in allodynia due to central lesion.

Adult↗

PubMed2006

Pilomotor seizures associated with sequential changes in magnetic resonance imaging.

Piloerection is rarely described in seizures. This symptom has been most frequently observed in patients with temporal lobe epilepsy and is rarely the principal clinical feature of seizures. No specific etiology of epilepsy associated with pilomotor seizures has been reported. We present the first case of a patient who experienced sudden and transitory epilepsy with pilomotor seizures occurring several times a day for months, and associated with sequential changes of the left hippocampus demonstrated by magnetic resonance imaging. [Published with video sequences].

Adult↗

PubMed2005

Septic thrombosis of the transverse and sigmoid sinuses: imaging findings.

The purpose of this study was to evaluate the contribution of magnetic resonance imaging (MRI) to the diagnosis of septic thrombosis of transverse and sigmoid sinuses to analyze the different steps of the diagnosis and to identify the origin of the difficulties in diagnosis. This retrospective study included eight patients aged 53-81 years (mean age: 61.9 years) with proven or highly probable septic thrombosis of transverse and sigmoid sinuses. All patients underwent a pre- and post-contrast enhancement brain CT scans and MRI. MR venogram (n=4) and HRCT of the temporal bone were performed when diagnosis was under discussion. After admission, the delay in diagnosis of lateral sinus thrombosis ranged from 8 to 60 days, with an average of 27 days (SD: +/-12.8). The delay in diagnosis was mainly due to non focused CT scans (6/8) or MR images performed at the initial presentation and absence of systematic radiological reading of the related fatty spaces and of skull base in bone windows (3/8). Diagnosis of septic origin of the thrombosis is of great importance, as it completely modifies the therapeutic planning of the patients. However, it remains a difficult challenge due to its lack of suggestive neurological or otolaryngologic symptoms.

Aged↗

PubMed2005

Spontaneous intracerebral hematoma on diffusion-weighted images: influence of T2-shine-through and T2-blackout effects.

BACKGROUND AND PURPOSE: On diffusion-weighted (DW) images, primary hematomas are initially mainly hyperintense, and then hypointense during the first few days after stroke onset. As in other brain disorders, variations in the T2 relaxation time of the hematoma influence the DW imaging signal intensity. Our aim was to evaluate the contribution of the T2 signal intensity and apparent diffusion coefficient (ADC) changes to signal intensity displayed by DW imaging through the course of hematoma. METHODS: The MR images of 33 patients with primary intracranial hemorrhage were retrospectively reviewed. Variations in T2-weighted echo planar images, DW imaging signal intensity, and apparent diffusion coefficient (ADC) ratios (core of hematoma/contralateral hemisphere) were analyzed according to the putative stages of hematoma, as seen on T1- and T2-weighted images. RESULTS: On both T2-weighted echo planar and DW images, the core of the hematomas was hyperintense at the hyperacute (oxyhemoglobin, n = 11) and late subacute stages (extracellular methemoglobin, n = 4), while being hypointense at the acute (deoxyhemoglobin, n = 11) and early subacute stages (extracellular methemoglobin, n = 7). There was a positive correlation between the signal intensity ratio on T2-weighted echo planar and DW images (r = 0.93, P < .05). ADC ratios were significantly decreased in the whole population and in each of the first three stages of hematoma, without any correlation between DW imaging findings and ADC changes (r = 0.09, P = .6). CONCLUSION: Our results confirm that the core of hematomas is hyperintense on DW images with decreased ADC values at the earliest time point, and may thus mimic arterial stroke on DW images. T2 shine-through and T2 blackout effects contribute to the DW imaging findings of hyperintense and hypointense hematomas, respectively, while ADC values are moderately but consistently decreased during the first three stages of hematoma.

Adult↗

PubMed2005

[Use of the functional imaging modalities in radiation therapy treatment planning in patients with glioblastoma].

Glioblastoma multiforme still remains, at present, the most frequent and deadly primary malignant glioma in adult. Despite safer and larger neurosurgical resections, patients almost always relapse very close or inside the tumor bed. Since more than 20 years, radiation therapy (RT) continue delivering the same dose of 60 Gy in 6 weeks, more precisely guided with CT-scanner and magnetic resonance imaging (MRI) in the treatment position. If morbidity has decreased with "non whole-brain" volumes, RT is nearly always failing locally, as surgery. Until now, all the series evaluating escalating doses (up to 80-90 Gy) in limited volumes have failed. One can really question : is the good dose delivered in the adequate volume? Main goal of new imaging techniques is to better visualize microscopic extension of malignant glioma cells. As based on metabolic principles, areas of abnormalities visualized with functional imaging have a different meaning, often complementary from conventional data. The four evaluated techniques are : magnetic resonance spectroscoy (MRS), functional MRI (fMRI), 18FDG or methionine PET, IMT (123iodine-alpha-methyl-thyrosine) SPECT. Each technique has potential interests and limits, MRS and fMRI appearing the most promising : they have both acceptable spatial resolution and can be executed just after conventional MRI acquisition. Areas of functional abnormalities are only partially including areas of hyperintensity in T1, T2 weighted MRI. It is therefore highly possible that, using it complementary to conventional CT and MRI for RT treatment planning, they add some precious informations; consequently, the very limited efficacy/toxicity ratio could be increased. This hypothesis will only be confirmed by prospective studies registering in parallel both functional and morphological abnormalities, linking them with sites of local recurrence. Once "targeted" the real microscopically invaded areas, one can speculate on new escalating dose studies, delivering RT in "adequate" volumes, combining it with new "targeted" drugs, as already recently demonstrated in head and neck cancers.

Brain Neoplasms↗

PubMed2005

MR diffusion tensor imaging, fiber tracking, and single-voxel spectroscopy findings in an unusual MELAS case.

A 23-year-old man was admitted to the intensive care unit for respiratory failure, global lower and upper limb palsy, and higher cognitive function deterioration. Imaging, performed with a combination of the MR diffusion tensor imaging, fiber tracking, and MR spectroscopy, suggested the diagnosis of an acute severe unusual mitochondrial encephalopathy, lactic acidosis, and strokelike event, which was confirmed by muscle biopsy, but fiber tracking showed unexpected unaltered white matter tracts.

Adult↗

PubMed2004

Management of pituitary apoplexy.

Pituitary apoplexy is a rare clinical syndrome caused by sudden haemorrhaging or infarction of the pituitary gland, generally within a pituitary adenoma. Headache of sudden and severe onset is the main symptom, associated with visual disturbances or ocular palsy. Signs of meningeal irritation or altered consciousness may complicate the diagnosis. Corticotropic deficiency (secondary adrenal failure) may be life-threatening if untreated. Computed tomography (CT) or magnetic resonance imaging (MRI) confirm the diagnosis by revealing a pituitary tumour with haemorrhagic and/or necrotic components: CT is most useful in the acute setting (24 - 48 h), MRI is useful for identifying blood components in the subacute setting (4 days to 1 month). Owing to the highly variable course of this syndrome and the limited individual experience, the optimal management of acute pituitary apoplexy is controversial. Some authors advocate early transphenoidal surgical decompression for all patients, whereas others adopt a more conservative approach for selected patients (those without visual acuity or field defects and with normal consciousness). Glucocorticoid treatment must always be initiated immediately, at a dose of hydrocortisone 50 mg every 6 h.

Headache↗

PubMedDate not supplied

MR diffusion tensor imaging and fiber tracking in spinal cord compression.

BACKGROUND AND PURPOSE: Spinal cord damage can result in major functional disability. Alteration of the spinal cord structural integrity can be assessed by using diffusion tensor imaging methods. Our objective is to evaluate the diagnostic accuracy of apparent diffusion coefficient (ADC), fractional anisotropy (FA), and fiber tracking in both acute and slowly progressive spinal cord compressions. METHODS: Fifteen patients with clinical symptoms of acute (n = 2) or slowly progressive (n = 13) spinal cord compression and 11 healthy volunteers were prospectively selected. We performed T2-weighted fast spin echo (FSE) and diffusion tensor imaging by using a 1.5-T MR scanner. ADC and FA maps were computed. Regions of interest were placed at the cervical, upper and lower thoracic cord levels for the healthy subjects and on the area with abnormal T2-weighted signal intensity in the patients with cord compression. In three patients, we used fiber tracking to locate the areas of cord compression precisely. Data were analyzed by using a mixed model. The sensitivity (SE) and specificity (sp) of imaging (T2, ADC, and FA maps) in the detection of spinal cord abnormality were statistically evaluated. RESULTS: For the healthy subjects, averaged ADC values ranged from 0.96 10(-3) mm(2)/s to 1.05 10(-3) mm(2)/s and averaged FA values ranged from 0.745 to 0.751. Ten patients had decreased FA (0.67 +/- 0.087), and one had increased FA values (0.831); only two patients had increased ADC values (1.03 +/- 0.177). There was a statistically significant difference in the FA values between volunteers and patients (P = .012). FA had a much higher sensitivity (SE = 73.3%) and specificity (sp = 100%) in spinal cord abnormalities detection compared with T2-weighted FSE imaging (se = 46.7%, sp = 100%) and ADC (SE = 13.4%, sp = 80%). CONCLUSIONS: FA has the highest sensitivity and specificity in the detection of acute spinal cord abnormalities. Spinal cord fiber tracking is a useful tool to focus measurements on the compressed spinal cord.

Acute Disease↗