The value of navigation-guided rTMS for the treatment of depression: An illustrative case

Repetitive transcranial magnetic stimulation (rTMS) of the prefrontal cortex has been thought to have great potential to treat refractory depression since the first studies published ten years ago. However, one of the potential limitations of rTMS is the poor definition of the localization of the prefrontal cortical target, which is based on a rather simplistic anatomical approach, i.e., 5 cm anterior to the primary motor cortical representation of the hand. This “standard procedure” does not take into consideration interindividual variations in brain morphology. We report the case of a 40-year-old woman who underwent two weeks of 10 Hz-rTMS for the treatment of a major, drug-resistant depressive episode. The rTMS target was determined with the “standard procedure” for the first week and with a dedicated navigation system as the left Brodmann area 46 for the second week. The clinical assessment of antidepressant effects was performed before and after each week of stimulation. Following the first week of stimulation, the patient improved, in particular regarding speech production. Using the navigation system, the location of the target stimulated during the first week was found to correspond to Broca's area, and not to the prefrontal area as intended. Antidepressant effects were more marked after the second week of navigated rTMS. In the present case, the prefrontal target was situated 8.3 cm anterior to hand motor cortex. This illustrates that the “standard procedure” may inaccurately target the prefrontal cortex, although resulting in antidepressant-like effects. The use of navigation systems should limit the variability of the results reported so far in the treatment of depression by rTMS. Le potentiel de la stimulation magnétique transcrânienne répétitive (SMTr) du cortex préfrontal pour traiter les dépressions résistantes est connu depuis dix ans. Cependant, une des limites de la SMTr est la définition anatomique simpliste de la cible préfrontale, 5 cm en avant de la représentation corticale motrice de la main. En effet, cette « procédure standard » ne prend pas en compte les variations interindividuelles de la morphologie du cerveau. Nous rapportons le cas d’une femme de 40 ans qui bénéficia du traitement d’un épisode de dépression majeure résistante par deux semaines de séances quotidiennes de SMTr à 10 Hz. La cible préfrontale fut déterminée par la « procédure standard » pour la première semaine de traitement et dans l’aire 46 de Brodmann par un sys