Temporal lobe association fiber tractography as compared to histology and dissection.

OBJECTIVES: To compare the temporal lobe white matter fiber bundles obtained by diffusion tensor imaging-based tractography to that by histology and dissection, and to study the interindividual variability of the obtained tracts. MATERIALS AND METHODS: DTI (diffusion tensor imaging) acquisitions (30 directions) were obtained from nine healthy volunteers. Imaging post-processing was performed with FSL (FMRIB Software Library) software. Uncinate fasciculus, longitudinal inferior fasciculus and optic radiations were tracked after positioning of the region of interest (ROI) in predetermined anatomical landmarks. Histological data were obtained by cutting 15 µm coronal sections in one left brain hemisphere and staining with modified Heidenhain-Woelcke myelin stain. Dissection was performed on the left brain hemisphere prepared in accordance with the Klingler method. Tractography of each bundle was compared to histology and dissection data. To highlight the interindividual variability of the considered fiber tracts, all the images were affinely registered on an arbitrarily chosen reference image by considering the B0 images. Fiber tracts were then warped according to the corresponding estimated transformation and an average fiber tract image was then computed. RESULTS: Our results demonstrated a good concordance between tractography of the temporal lobe white matter bundles and dissection and histological data. The interindividual reproducibility of each tract seemed to be good, particularly in the middle part. The variability was more important at both ends, probably in relation to the dispersion of fiber bundles. CONCLUSION: Diffusion tensor imaging-based tractography of temporal lobe white matter tracts seemed to be in accordance with histological and dissection data. Taking into account some limitations, it could be of particular interest for the presurgical planning of temporal lobectomy.

Venous thromboembolism and occult malignancy: simultaneous detection during pulmonary CT angiography with CT venography.

OBJECTIVE: We explored the potential for patients with proven venous thromboembolism or pulmonary embolism (PE) to have occult malignancies detected during the same CT examination. To verify this, we compared the presence of occult malignancies identified on pulmonary artery CT angiography (CTA) and CT venography (CTV) when venous thromboembolism (VTE) was present. SUBJECTS AND METHODS: Pulmonary artery CTA combined with CTV was performed on a 16-MDCT scanner on 186 adult patients suspected of having pulmonary embolism without any known malignancies. CTV was performed from the diaphragm to the knee 180 seconds after CTA. Two radiologists evaluated the presence of VTE, that is PE or deep venous thrombosis (DVT), and tumor lesions on both examinations in consensus. The malignant nature of the possibly identified tumors was confirmed by pathologic examination. RESULTS: VTE was found in 49 patients (26%). Malignant tumors were detected in 24 patients (13%). Eleven patients with malignant tumors had VTE (46% of patients with malignant tumors; 22% with VTE and 6% of all patients). There was correlation with presence of malignancies between both and DVT and DVT associated with PE but not between presence of malignancies and PE only. Patients with DVT and those with DVT associated with PE had a risk ratio of 3.2 and 3.3, respectively, for having a malignant tumor discovered simultaneously. CONCLUSION: A high number of malignant tumors can be incidentally discovered on pulmonary artery CTA, even more so with additional CTV. Radiologists should scrutinize scans to pick up unknown malignancies, especially in patients with identified VTE.

Cellular magnetic resonance imaging for the differentiation of infectious and degenerative vertebral disorders: preliminary results.

PURPOSE: To evaluate macrophage imaging using the ability of superparamagnetic iron oxide (SPIO) magnetic resonance imaging (MRI) to differentiate infectious vertebral osteomyelitis and degenerative disk-related inflammatory endplates. The in vivo demonstration of the different distribution of macrophages in those two disorders may allow a more accurate characterization of vertebral endplate abnormalities than classical extracellular MR changes. MATERIALS AND METHODS: In 12 patients with endplate abnormalities (six cases of bacteriologically proven spondylodiscitis, six cases of disk degeneration-related endplate changes), two MRI sessions were realized: before and 24 hours after injection of SPIO. The signal-to-noise ratio (SNR) of endplates were qualitatively and quantitatively compared on pre- and post-SPIO injection T1 and T2-weighted (T2w) MR images (Wilcoxon signed rank test). RESULTS: In the infection group, the SNR of abnormal endplates showed a significant signal loss on T2w MR images (P = 0.03) but not on T1w images (P = 0.46). In the degenerative spine group, no significant signal loss was observed on T1 (P = 0.6) nor on T2w MR images (P = 0.6). Signal loss was only visually observable in abnormal endplate in one patient of the spondylodiscitis group on T2w MR images. CONCLUSION: MRI of the spine with iron oxide injection differentiates infection from aseptic inflammation on quantitative analysis, but the use of SPIO makes direct visual evaluation less satisfactory.

Mice with a mutation in the dynein heavy chain 1 gene display sensory neuropathy but lack motor neuron disease.

In neurons, cytoplasmic dynein functions as a molecular motor responsible for retrograde axonal transport. An impairment of axonal transport is thought to play a key role in the pathogenesis of neurodegenerative diseases such as amyotrophic lateral sclerosis, the most frequent motor neuron disease in the elderly. In this regard, previous studies described two heterozygous mouse strains bearing missense point mutations in the dynein heavy chain 1 gene that were reported to display late-onset progressive motor neuron degeneration. Here we show, however, that one of these mutant strains, the so-called Cra mice does not suffer from motor neuron loss, even in aged animals. Consistently, we did not observe electrophysiological or biochemical signs of muscle denervation, indicative of motor neuron disease. The "hindlimb clasping" phenotype of Cra mice could rather be due to the prominent degeneration of sensory neurons associated with a loss of muscle spindles. Altogether, these findings show that dynein heavy chain mutation triggers sensory neuropathy rather than motor neuron disease.

Diffusion-weighted MRI of denervated muscle: a clinical and experimental study.

OBJECTIVE: The aim of this study was to investigate skeletal muscle denervation using diffusion-weighted magnetic resonance imaging (DWMRI). MATERIALS AND METHODS: Sciatic nerve axotomy was performed in a group of nine New Zealand White rabbits, and electromyographic (EMG), pathological, and DWMRI studies were conducted on ipsilateral hamstring muscles 1 and 8 days after axotomy. In addition, DWMRI studies were carried out on leg muscles of ten patients with acute and subacute lumbosacral radiculopathy. RESULTS: High intensity signals on short tau inversion recovery (STIR) magnetic resonance imaging and an increased apparent diffusion coefficient (ADC) were observed in denervated muscles of the animals 1 and 8 days after axotomy as well as in denervated muscles of the patients with radiculopathy. In the clinical study, ADC was 1.26 +/- 0.18 x 10(-9) m(2)/s in normal muscle and increased to 1.56 +/- 0.23 x 10(-9) m(2)/s in denervated muscles (p = 0.0016). In animals, EMG and muscle pathological studies were normal 1 day after axotomy, and the muscles demonstrated spontaneous activity on EMG and neurogenic atrophy on histological studies 7 days later. CONCLUSION: This DWMRI study demonstrates that enlargement of extracellular fluid space in muscle denervation is an early phenomenon occurring several days before the appearance of EMG and histological abnormalities.