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Published on: July 2, 2013
Tracing volitional recovery in post-stroke akinetic mutism using longitudinal microstructure imaging: Insights from a
Jie Zhang1, Yingqiao Wang2, Zhenyu Shu3
1Center for Rehabilitation Medicine, Rehabilitation and Sports Medicine Research Institute of Zhejiang Province, Department of Rehabilitation Medicine, Zhejiang Provincial People's Hospital (Affiliated People's Hospital), Hangzhou Medical College, Hangzhou, China; Wellcome Center for Human Neuroimaging, Department of Imaging Neuroscience, Institute of Neurology, University College London, London, UK.
Abstract:
Lesions in the frontal-subcortical circuitry can lead to akinetic mutism (AM) characterized by diminished volition. However, the microstructural changes in the damaged network underlying its recovery remain unknown. Clinical examination and neuropsychological assessment were performed on a patient with post-stroke AM. Multimodal MRI scans were performed at baseline and follow-ups. We used diffusion MRI and biophysical models, specifically utilizing neurite orientation dispersion and density imaging for assessing gray matter microstructure, and fixel-based analysis for the evaluation of white matter. Longitudinal comparisons were performed between the patient and healthy controls. Pronounced recovery of volition was observed after dopamine agonist therapy combined with physical therapy. In addition to infarcts in the bilateral medial cortex, microstructure imaging detected reduced neurite density in extensive areas, specifically in temporal areas and subcortical nuclei, and decreased fiber density of white matter tracts (TFCE-corrected p < .05). Microstructural degeneration in the anterior cingulate cortex and cingulum was relatively persistent (Bonferroni-corrected p < .05). However, most tracts within the frontal-subcortical circuitry showed increased fiber density during the recovery stage. Microstructure of an extensive network may contribute to the disruption and recovery of volition. Fiber density within the frontal-subcortical circuitry could be a promising biomarker indicating volitional recovery.
Insights
Akinetic mutism (AM) recovery involves widespread brain network changes. Increased white matter fiber density in the frontal-subcortical circuitry may serve as a biomarker for improved volition.
Area of Science:
- Neuroimaging
- Neurology
- Neuroscience
Background:
- Akinetic mutism (AM) results from frontal-subcortical circuitry damage, causing reduced volition.
- The microstructural brain changes during AM recovery are not well understood.
Observation:
- A patient with post-stroke AM underwent clinical, neuropsychological, and multimodal MRI assessments.
- Diffusion MRI and biophysical models (neurite orientation dispersion and density imaging, fixel-based analysis) were used for microstructure analysis.
- Longitudinal data from the patient were compared with healthy controls.
Findings:
- Reduced gray matter neurite density and white matter fiber density were observed in extensive brain areas, including temporal regions and subcortical nuclei.
- Persistent microstructural degeneration was noted in the anterior cingulate cortex and cingulum.
- Most frontal-subcortical tracts showed increased fiber density during recovery, correlating with improved volition after dopamine agonist and physical therapy.
Implications:
- Brain network microstructure plays a crucial role in the disruption and recovery of volition.
- Increased fiber density in the frontal-subcortical circuitry shows potential as a biomarker for volitional recovery in akinetic mutism.
