[Operative and perioperative aspects of deep brain stimulation]. / Aspects opératoires et péri-opératoires de la stimulation cérébrale profonde.

Deep brain stimulation (DBS) requires the surgical implantation of a system including brain electrodes and impulsion generator(s). The nuclei targeted by the stereotaxic implantation methodology have to be visualized at best by high resolution imaging. The surgical procedure for implanting the electrodes is performed if possible under local anaesthesia to make electro-physiological measurements and to test intra-operatively the effect of the stimulation, in order to optimize the position of the definitive electrode. In a second step, the impulsion generator(s) are implanted under general anaesthesia. DBS for movement disorders has a very good efficacy and a low albeit non-zero risk of serious complications. Complications related to the material are the most common.

Magnetic resonance imaging techniques in white matter disease: potentials and limitations.

OBJECTIVES: excellent soft tissue contrast, noninvasiveness, assessment of multiple structural and functional parameters, and absence of radiation are the essential properties of magnetic resonance imaging explaining why this modality is the technique of choice for the assessment of cerebral white matter (WM). METHODS: the present review discusses various standard and advance magnetic resonance imaging techniques with respect to WM assessment in a clinical context. Techniques assessing predominantly structure are T2, fluid-attenuated inversion recovery, echo-gradient T2*, and susceptibility weighted imaging. Techniques assessing a mix between structure and function are diffusion-weighted and diffusion tensor imaging to investigate WM tracts, magnetization transfer to assess bound and free water pool, and magnetic resonance spectroscopy investigating brain metabolites. Finally, functional techniques are perfusion-weighted imaging and perfusion reserve imaging to assess cerebral perfusion and cerebral perfusion reserve, respectively. CONCLUSIONS: magnetic resonance imaging may assess various and complementary WM parameters. Because acquisition time is limited in the clinical setting, MR techniques must be adapted to the primary question asked. The basic imaging of WM might include axial T2, diffusion-weighted imaging, and coronal fluid-attenuated inversion recovery. This provides an excellent overview in a relatively short time and 2 imaging planes. The remaining MR techniques can add complementary information, for example, PWI/perfusion reserve imaging in vascular disease, T2*/susceptibility weighted imaging in degenerative disease (iron deposition) and head trauma (microbleeds), magnetic resonance spectroscopy (metabolic disease and neoplasm), magnetization transfer (demyelinating disease), and diffusion tensor imaging (degenerative diseases, presurgical evaluation).