Abstract
OBJECTIVES/HYPOTHESES: To determine whether transcutaneous electrical nerve stimulation (TENS) provides adequate, inexpensive and simple means to image innocuous and pain-related activations in the thalamus and cortex.SUBJECTS AND METHODS: High resolution functional magnetic resonance imaging (fMRI) was used to obtain functional data sets on a 1.5T General Electric echospeed scanner (General Electric, Milwaukee) from six axial slices during interleaved periods of rest and TENS at either nonpainful tingling or painful intensities. The volume of brain imaged allowed inspection of stimulation-related activations in the thalamus, insula and second somatosensory cortex (S2).RESULTS: Tingling TENS activations were identified primarily in the contralateral posterolateral thalamus. Painful TENS activations were found in the contralateral posterolateral thalamus, medial and/or anterior thalamus. The insula and S2 were activated in four of the subjects with tingling TENS and in all subjects with painful TENS. Tingling TENS activations were located in the posterior insula, whereas pain-related activations were located in the anterior insula. Painful TENS activations found in S2 overlapped with tingling TENS activations.CONCLUSIONS: These findings demonstrate that TENS is a simple mode of stimulation that produces fairly consistent cortical activations, especially at painful levels, and thus may be useful in carefully designed and controlled clinical fMRI studies of pain and touch.