(Re)organisation of the somatosensory system after early brain lesion: A lateralization index fMRI study

Objective: To evaluate the relationship between neural (re)organization of the somatosensory cortex and impairment of sensory function (2-point discrimination [2PD]) in individuals with unilateral cerebral palsy.

Methods: We included 21 individuals with unilateral cerebral palsy. 2PD thresholds were evaluated on thumb pads, and activation of the somatosensory cortex was recorded by functional MRI (fMRI) during passive movements of the affected hand. A lateralization index (LI) was calculated for the primary sensory (S1) and secondary sensory (S2) cortices and the correlation between the LI and 2PD thresholds was analysed.

Results: We found a significant negative correlation between the 2PD thresholds and the S2 LI (r=-0.5, one-tailed P-value=0.01) and a trend towards a negative correlation with the S1 LI (r=-0.4, one-tailed P-value=0.05).

Conclusion: High levels of activation in the contralesional hemisphere were associated with high levels of sensory impairment in individuals with unilateral cerebral palsy. The interhemispheric (re)organization of the somatosensory system may not effectively compensate for somatosensory impairment.