Uncinate fasciculus — MRCPsych Paper A MCQ

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HardNeuroanatomyUncinate fasciculusMRCPsych Paper A

A 33-year-old man develops disinhibition and impaired emotion-based decision-making after a focal traumatic brain injury. Diffusion tractography shows disruption of ventral association fibres that pass through the region of the limen insulae, linking the temporal pole and anterior amygdala with the lateral orbitofrontal and frontopolar cortex. Which tract is most likely to have been damaged?

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Correct answer: A — Uncinate fasciculus

The correct answer is A, the uncinate fasciculus. This ventral association tract links the temporal pole and anterior temporal limbic structures, including the amygdala, with the lateral orbitofrontal and frontopolar cortex. Its disruption can impair the use of emotional and mnemonic information to guide behaviour, contributing to disinhibition and poor social-emotional decision-making. The arcuate fasciculus primarily supports dorsal language connections. The cingulum runs within the cingulate and parahippocampal regions rather than connecting the temporal pole directly to orbitofrontal cortex. The inferior fronto-occipital fasciculus connects occipital and posterior temporal regions with frontal cortex. The inferior longitudinal fasciculus connects occipital and temporal visual-association regions without an orbitofrontal termination.

Reference: Von Der Heide RJ, Skipper LM, Klobusicky E, Olson IR. Dissecting the uncinate fasciculus: disorders, controversies and a hypothesis. Brain. 2013;136(6):1692–1707. https://pubmed.ncbi.nlm.nih.gov/23649697/