Magnetic resonance imaging stereotactic thalamotomy: report of a case with comparison to computed tomography

The anatomical location of the thalamic target (ventrolateral nucleus) during stereotactic thalamotomy for a movement disorder was determined using magnetic resonance imaging (MRI) to define the anterior and posterior commissures and the intercommissural plane. Precise targeting was confirmed by intraoperative stereotactic computed tomography (CT), electrophysiological stimulation, and a gratifying postoperative response (disappearance of contralateral tremor and rigidity). The use of a MRI- and CT-compatible stereotactic coordinate frame allowed multiplanar imaging with excellent spatial and contrast resolution, visualization of the source of the tremor (prior embolic stroke affecting the dentatorubrothalamic pathway), and correction for the more medial location of the internal capsule in this patient. Location did not vary among target sites seen with MRI and CT imaging techniques. In this patient MRI during stereotactic thalamotomy supplemented CT and the electrophysiological technique that we conventionally use to define the ventrolateral nucleus. Although the importance of possible magnetic susceptibility imaging artifacts remains to be elucidated, stereotactic MRI may prove sufficiently accurate in the future to replace other imaging techniques used during functional neurosurgery.