Cortical activation during finger tapping in thyroid dysfunction: a functional magnetic resonance imaging study

Thyroid dysfunction is associated with attention deficit and impairment of the motor system (muscle weakness and fatigue). This paper investigates possible motor function deficit in thyroid patients,compared to the controls. Functional MRI studies (fMRI)were carried out in five hypo and five hyperthyroid patients and six healthy volunteers. Whole brain imaging was performed using echo planar imaging (EPI)technique, on a 1.5T whole body MR system (Siemens Magnetom Vision). The task paradigm consisted of 8 cycles of active and reference phases of 6 measurements each, with right index finger tapping at a rate of 120 taps/min. Post-processing was performed using statistical parametric mapping on a voxel-by-voxel basis using SPM99. Clusters of activation were found in the contralateral hemisphere in primary somatomotor area (M1), supplementary motor area (SMA), somatosensory,auditory receptive and integration areas, inferior temporal lobe, thalamus and cerebellum. Increased clusters of activation were observed in M1 in thyroid subjects as compared to controls and with bilateral activation of the primary motor cortex in two hyperthyroid patients. The results are explained in terms of increased functional demands in thyroid patients compared to volunteers for the execution of the same task.