Reduced functional connectivity of somatosensory network in writer's cramp patients

Background: The involvement of motor cortex and sensorimotor integration in patients with writer's cramp (WC) has been well documented. However, the exact neurophysiological profile within the somatosensory system, including primary somatosensory cortex (SI), contralateral (SIIc), and ipsilateral (SIIi) secondary somatosensory areas remains less understood. Methods: This study investigated the neuromagnetic cortical activities of median nerve stimulation in 10 patients with WC and 10 healthy controls (HC). To comprehensively explore all the aspects of somatosensory functioning, we analyzed our data with the minimum norm estimate (MNE), the time-frequency approach with evoked and induced activities, and functional connectivity between SI and SIIc (SI-SIIc), SI and SIIi (SI-SIIi), and SIIc and SIIi (SIIc-SIIi) from theta to gamma oscillations. Results: No significant between-group differences were found in the MNE cortical amplitudes of SI, SIIc, and SIIi. Power strengths of evoked gamma oscillation and induced beta synchronization were also equivalent between WC and HC groups. However, we found significantly reduced theta coherence of SI-SIIi, alpha coherence of SI-SIIi and SIIc-SIIi, as well as beta coherence of SIIc-SIIi in patients with WC. Conclusion: Our results suggest the involvement of somatosensory abnormalities, primarily with the form of functional connectivity, in patients with WC.