Misleading functional magnetic resonance imaging mapping of the cortical hand representation in a 4-year-old boy with an arteriovenous malformation of the central region.

Functional MR imaging is dependent on the hemodynamic response function of the brain. Cerebrovascular anomalies may lead to hemodynamic artifacts, contorting the true localization of neural activation. This is illustrated in the case of a 4-year-old boy with an arteriovenous malformation (AVM) of the left central region undergoing extensive functional mapping prior to surgical removal. Intraoperative electrophysiological recording confirmed presurgical results of magnetoencephalography (MEG) and transcranial magnetic stimulation (TMS) examinations, detecting the sensorimotor hand representation within the brain tissue into which the AVM extended, whereas the activation demonstrated by functional MR (fMR) imaging was proven to be falsely localized by that modality, which showed it to be posterior to the affected central region. Thus, this case demonstrates that functional mapping can be performed even in very young patients and that combining fMR imaging with TMS and MEG is especially important in patients with vascular lesions, in whom fMR imaging can be misleading due to changes in blood flow.