Verifying the hypothesis of disconnection syndrome in patients with conduction aphasia using diffusion tensor imaging

BACKGROUND： It is thought in disconnection theory that connection of anterior and posterior language function areas, i.e. the lesion of arcuate fasciculus causes conduction aphasia. OBJECTIVE： To verify the theory of disconnection elicited by repetition disorder in patients with conduction aphasia by comparing the characteristics of diffusion tensor imaging between healthy persons and patients with conduction aphasia. DESIGN： Case-control observation. SETTING： Department of Neurology, Hongqi Hospital Affiliated to Mudanjiang Medical College. PARTICIPANTS： Five male patients with cerebral infarction-involved arcuate fasciculus conduction aphasia, averaged （43±2） years, who hospitalized in the Department of Neurology, Hongqi Hospital Affiliated to Mudanjiang Medical College from February 2004 to February 2005 were involved in this experiment. The involved patients were all confirmed as cerebral infarction by skull CT and MRI, and met the diagnosis criteria revised in 1995 4^th Cerebrovascular Conference. They were examined by the method of Aphasia Battery of Chinese （ABC） edited by Surong Gao. The results were poorer than auditory comprehension disproportionately, and consistented with the mode of conduction aphasia. Another 5 male healthy persons, averaged （43 ± 1 ） years, who were physicians receiving further training in the Department of Neurology, Beijing Tiantan Hospital were also involved in this experiment. Informed consents of detected items were obtained from all the subjects. METHODS： All the subjects were performed handedness assessment with assessment criteria of handedness formulated by Department of Neurology, First Hospital Affiliated to Beijing Medical University. Arcuate fasciculus of involved patients and health controls were analyzed with diffusion tensor imaging （DTI） and divided into 3 parts （anterior, middle and posterior segments） for determining FA value （mean value was obtained after three times of measurements）, and a comparison of FA value was made between two sides. MAIN OUTCOME MEASURES： Analysis results of arcuate fasciculus DTI of healthy controls and patients with conduction aphasia. RESULTS： Five patients with conduction aphasia and 5 healthy controls participated in the final analysis. ①All the subjects were right-handedness.② The left FA value of anterior, middle and posterior segments of arcuate fasciculus was larger than the right one in most normal volunteers, i.e. arcuate fasciculus with normal function on the left side was more than that on the right side. Because the amount of healthy controls was small, so positive conclusion has not been obtained, and only above-mentioned tendency was demonstrated. Healthy controls had good bilateral arcuate fasciculus; Three patients with conduction aphasia presented left FA value of anterior segment of arcuate fasciculus smaller than the right one, and two patients presented the left FA value larger than the right one. Four patients presented the left FA value of middle segment of arcuate fasciculus smaller than the right one, and one patient presented the left FA value larger than the right one, i.e. middle segment of arcuate fasciculus of 5 patients with conduction aphasia was all involved in at different degrees. Four patients with conduction aphasia presented the left FA value of posterior segment of arcuate fasciculus smaller than the right one, and one patient presented the left FA value larger than the right one, i.e. posterior segment of arcuate fasciculus of 5 patients was all injured at different degrees. CONCLUSION： Arcuate fasciculus of patients with conduction aphasia all is involved in at different degrees, which verifies the theory of disconnection of repetition disorder in patients with conduction aphasia.