Arcuate Fasciculus Lesion and Neurologic Examination Findings
This patient will most likely have difficulty repeating words and phrases back to you. The arcuate fasciculus is the critical white matter pathway connecting posterior temporal language areas with frontal motor speech regions, and its disruption characteristically impairs repetition abilities while relatively preserving other language functions.
Anatomical and Functional Basis
The left arcuate fasciculus serves as the primary dorsal language pathway connecting temporal, parietal, and frontal language regions 1. Structural damage to the arcuate fasciculus in the acute phase is specifically associated with impaired repetition, along with dysfunction in Broca's area and the inferior portion of the left supramarginal gyrus 1.
Multiple studies confirm that posterior temporal-parietal lesions with damage to the dorsal superior longitudinal and arcuate fasciculus produce repetition deficits 1. This pattern differs from comprehension deficits, which are instead associated with ventral extreme capsule fiber damage 1.
Why Repetition is Specifically Affected
The arcuate fasciculus plays a critical role in phonological processing and the transmission of auditory-phonological information from posterior receptive areas to anterior motor speech regions 2, 3:
- The long segment of the arcuate fasciculus contributes specifically to naming abilities 2
- The posterior segment is most crucial for comprehension and residual language abilities 2, 3
- Nonword repetition tasks are particularly sensitive to arcuate fasciculus integrity, detecting subtle phonological processing errors that may not appear in standard picture naming 4
The arcuate fasciculus lesion load negatively influences speech production and classifies severe versus non-severe outcomes with 90% accuracy for naming and 96% accuracy for speech fluency 1.
Why Other Options Are Less Likely
Comprehending instructions would be relatively preserved because comprehension deficits correlate with blood flow in Wernicke's area and ventral extreme capsule fiber damage, not primarily arcuate fasciculus lesions 1, 5.
Expressing thoughts fluently would be less affected because fluency deficits are more associated with anterior segment damage and Broca's area lesions rather than isolated arcuate fasciculus involvement 2.
Perceiving the left half of surroundings (hemineglect) would not occur with a left hemisphere lesion; unilateral spatial neglect occurs with right hemisphere damage to the fronto-parietal segment of the arcuate fasciculus and superior longitudinal fasciculus 1.
Writing a sentence may show some impairment, but the hallmark deficit of arcuate fasciculus damage remains the disproportionate difficulty with repetition tasks compared to other language modalities 1, 6.
Clinical Implications
The volume of the left long segment of the arcuate fasciculus, combined with age, sex, and lesion size, improves prediction of language recovery at six months 1. Patients with more symmetric or right-lateralized arcuate fasciculus pathways demonstrate better preservation of language abilities after left hemisphere damage 7, suggesting potential compensatory mechanisms through right hemisphere homologs.