Objective
To investigate the activation pattern of somatosensory cortex in subcortical stroke patients underlying recovered somatosensory capacity of hand, using functional MRI (fMRI). Method: Four patients with subcortical cerebral hemorrhage or infarction and five normal healthy volunteers were investigated. Sensory task was given on the palm of hand by brushing as a frequency of 1 Hz. In fMRI study, ten slices were obtained using the Echo Planar Imaging technique, data was statistically analyzed using SPM-99 software. Results: During the tactile stimulation of affected hand, contralateral primary somatosensory cortex was activated inall the patients. In the two patients with full recovery of tactile sense, cortical activation for paretic hand was stronger than in nonparetic hand. On the other hand, the other two patients with incomplete recovery showed that cortical activation for nonparetic hand was stronger than in paretic hand and even normal control. Conclusion: Our result suggested that functional consequences of the somatosensory cortical area were not limited to the ipsilateral hemisphere to the lesion, but affect the contralateral, nonlesioned hemisphere, in subcortical stroke patients with recovered somatosensory capacity. (J Korean Acad Rehab Med 2005; 29: 445-449)

Objective
To investigate whether the somatosensory cortical excitability could be modulated by repetitive electrical stimulation (RES) on the tibial nerve at human ankle joint.

Method: The subjects were 10 healthy volunteers. The study was composed of 3 sessions: first session, baseline evaluation; second session, RES with a intensity for proprioceptive stimulation on tibial nerve at the right ankle for 3 different duration of 30 minutes, 1 hour, and 2 hours; third session, repeat of baseline evaluation after RES (post- RES evaluation). The baseline evaluation include somatosensory evoked potential study with stimulation of right tibial nerve and compound muscle action potential (CMAPs) of tibial nerve recorded at abductor hallucis and H reflex. The amplitude of each study were measured and compared between baseline evaluation and post-RES evaluation using Kruscal-Wallis test.

Results: There was no significant change in amplitudes of SSEP, CMAP and H reflex between baseline evaluation and post-RES evaluation of 30 minutes, 1 hour and 2 hours.

Conclusion: This study suggests that chronic repetitive proprioceptive afferent nerve stimulations could not modulate primary somatosensory cortex in healthy subjects. However, we could not rule out the limitations of sensitivity of somatosensory evoked potential study. (J Korean Acad Rehab Med 2003; 27: 224-227)