Time-course of Changes in Activation Among Facial Nerve Injury: A Functional Imaging Study

Patients suffering different intervals of facial nerve injury were investigated by functional magnetic resonance imaging to study changes in activation within cortex. Forty-five patients were divided into 3 groups based on intervals of facial nerve injury. Another 16 age and sex-matched healthy participants were included as a control group. Patients and healthy participants underwent task functional magnetic resonance imaging (eye blinking and lip pursing) examination. Functional reorganization after facial nerve injury is dynamic and time-dependent. Correlation between activation in sensorimotor area and intervals of facial nerve injury was significant, with a Pearson correlation coefficient of −0.951 (P < 0.001) in the left sensorimotor area and a Pearson correlation coefficient of 0.333 (P = 0.025) in the right sensorimotor area. Increased activation in integration areas, such as supramarginal gyrus and precunes lobe, could be detected in the early-middle stage of facial dysfunction compared with normal individuals. Decreased activation in sensorimotor area contralateral to facial nerve injury could be found in late stage of facial dysfunction compared with normal individuals. Dysfunction in the facial nerve has devastating effects on the activity of sensorimotor areas, whereas enhanced intensity in the sensorimotor area ipsilateral to the facial nerve injury in middle stage of facial dysfunction suggests the possible involvement of interhemispheric reorganization. Behavioral or brain stimulation technique treatment in this stage could be applied to alter reorganization within sensorimotor area in the rehabilitation of facial function, monitoring of therapeutic efficacy, and improvement in therapeutic intervention along the course of recovery.