The STS-centered network (1) is intrinsically connected during the brain resting, (2) encompasses the whole caudalmost two thirds of STS, (3) may partly represent the whole STS structural connectivity, and includes the motor and cognitive neocerebellum (lobules VI/VIIA).

The existence of the accessory middle cerebral artery (AMCA) is a rare anatomical variation with an estimated incidence of 0.31%. The embryological development of this artery is unknown. Three anatomical subtypes are described: in the type 1 variety the AMCA arises from the internal carotid artery; in the type 2, the AMCA originates from the proximal part of the anterior cerebral artery; in type 3, the AMCA arises from the distal part of the anterior cerebral artery. The use of endovascular techniques to treat cerebral vascular malformations requires knowledge of the anatomical subtype of AMCA and the brain regions it supplies (cortex, basal ganglia).

We investigated neurochemical abnormalities in the normal-appearing white matter (NAWM) on MRI of patients with optic neuritis (ON) and compared them to those of patients with multiple sclerosis (MS). Patients with ON (42) were classified into three groups according to abnormalities on brain MRI. Patients with MS (55) were divided in two groups: relapsing remitting MS (RRMS) and secondary progressive MS (SPMS). All patients underwent MRI of the brain and localised proton magnetic resonance spectroscopy (MRS) of NAWM. The results were compared to those of 15 controls. Patients with MS had significant abnormalities compared with controls and with patients with ON. Patients with RRMS and those with ON had comparable MRS parameters, while patients with SPMS had significant spectroscopic abnormalities in comparison with controls, but also with patients with RRMS. These changes consisted of a decrease in N -acetylaspartate, a neuronal marker, which may reflect axonal dysfunction and/or loss. MRS abnormalities were detected in 14 patients with ON (27 %). The main abnormalities consisted of a decrease in N -acetylaspartate, an increase in choline-containing compounds at long echo times, and the presence of free lipid peaks at short echo times. MRS of the NAWM on MRI may prove useful for detecting neurochemical brain abnormalities in ON not visible on MRI.

Using MRI, we demonstrated that the depiction of the cerebral white matter fiber tracts has become a routine procedure. Diffusion tensor (DT) sequences may be analyzed with combined volume analysis and tractography extraction software, giving indirect visualization of white matter connections. We obtained DT data from 20 subjects with normal MR imaging and five patients presenting cerebral diseases such as brain tumors, multiple sclerosis and stroke, with five patients explored on two different MR scanners. Data were transferred to dedicated workstations for anatomical realignment, determination of voxel eigenvectors and calculation of fiber tract orientations in a region of interest. In all subjects, axonal directions underlying the main neuronal pathways could be delineated. Comparisons between diseased regions and contralateral areas demonstrated changes in voxel anisotropy in injured regions, revealing possible preferential fiber orientations within diffuse T2 hyperintensities. Rapid data processing allows imaging of the normal and diseased fiber pathways as part of the routine MRI examination. Therefore, it appears that whenever white matter disease is suspected a tractography can be performed with this fast and simple method that we proved to be reliable and reproducible.

MRI is the most powerful imaging technique in managing patients with suspected or confirmed multiple sclerosis (MS). However, conventional MRI variables show nonspecific abnormalities weakly correlated with clinical progression of the disease. New techniques, now routinely available, offer better characterisation of the pathophysiology. We combined conventional MRI, including lesion load, contrast enhancement and "black holes" with magnetisation transfer and diffusion-weighted imaging and localised proton MR spectroscopy (MRS) to study their relationship with disability, course and duration of MS. The variables that were the most significantly linked to the course of the disease (relapsing remitting versus secondary progressive) were lesion load, mean overall magnetisation transfer ratio and apparent diffusion coefficient (MGADC), the percentage of ADC in (PADCIMD), and out of (PAD-COMD) modal distribution, and the ratio N-acetylaspartate and creatine-containing compounds on MRS of the centrum semiovale. MGADC and PADCIMD were the independent factors most related to disability and duration of disease. Combining MRI techniques is clinically relevant and feasible for studies of MS and may be applied to other diseases of the central nervous system.

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Knowledge of the radiological anatomy of the cranial dural vascularization allows a flexible and appropriate approach to the pretherapeutic investigation of cranial dural arteriovenous malformations. The variability of the origin of these arteries requires that several possible sources of vascular supply be investigated - internal carotid, internal maxillary, ascending pharyngeal, occipital and vertebral - and that each of their meningeal branches be known in detail. Finally, familiarity with the radiological anatomy of these vessels allows one to identify on routine angiography those vessels that may be a source of risk when performing techniques of endovascular therapy (pedicles supplying the cranial nerves, internal carotid and vertebral anastomoses). Each foramen at the base and vault of the cranium contains an artery to the dura mater. Accordingly, very precise topographical study, in particular of the cavernous region, can be made.

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