Fiber structure of language function areas in Broca aphasia In vivo assessment by diffusion tensor imaging and fiber tractography

Xuejin SUN; Xin WANG; Qing GU; Yumei ZHANG; Jianping DAI; Yanming BAO

ABSTRACT

BACKGROUND:

Diffusion tensor imaging aad fiber tractography(DT-FT)is the only method to identify cerebral white matter fiber organization in vivo.

OBJECTIVE:

To observe the changes in brain areas with language function and the fiber stucture in patients with Broca aphasia.DESIGN,TIME AND

SETTING:

Comparative observation was performed at First Hospital of Kunming Medical College and Tiantan Hospital of Capital Medical University between November 2003 and February 2005.

PARTICIPANTS:

Thirty patients(9 females,21 males,aged 17-63 years)with Broca aphasia of different degree were selected.They were diagnosed by a set of Chinese aphasia examinations of Research Laboratory of Neuropsychology,First Hospital of Beijing Medical University,following by further classification according to the subitems.

METHODS:

3T super-high field magnetic resonance scanner was used for the data collection and processing of the entire brain.Brodmann areas 45,44,areas 22 and 39(Wernicke area),and the corresponding brain areas in the right hemisphere are selected as areas with language function.The primary commissure,commissural fibers(arcuate fasciculus,internal capsule,external capsule)that are closely correlated with language function were regarded as region of interest of fiber tracking.The neural fiber tracking was conducted.MAIN OUTCOME MEASUIURESThe tracking and distribution of neural fiber tracts,and its correlation with other brain areas,and changes under pathological conditions.All data were compared with normal brain.

RESULTS:

Thirty patients with Broca aphasia were included in final analysis.The mean fractional anisotropy of fiber tracts in left Brodmann areas 45 and 44 was significantly lower than that in normal Brodmann areas(t=-2.683 65,-5.300 55,P＜0.05).The inferior fiber tracts in Broca area showed interruption or displacement,loosely connected even separate from the frontal arcuate fasciculus.The fibers of precentral gyrus and medial frontal lobe were decreased.The separation of arcuate fasciculus from Broca area caused by the integrity disruption and displacement of fiber tracts of arcuate fasciculus was the main alteration of arcuate fasciculus in Broca aphasia.The number of fiber tracts of left arcuate fasciculus and the mean fractional anisotropy in Broca aphasia were significantly less than normal people(P＜0.05).

CONCLUSION:

The lesions of cerebral cortex and its fiber pathway in Broca area can result in Broca aphasia.