Apraxia of Speech Assessment and Neuroanatomical Correlates

Apraxia of Speech (AOS) is a motor speech disorder characterised by impaired planning and programming of the complex oral movements required for intelligible speech. Assessment typically combines perceptual evaluation of articulatory errors—such as distorted substitutions, distorted segments and prosodic disturbances—with quantitative measures drawn from instrumental techniques. Neuroanatomical studies have converged on a core network centred on the left inferior frontal gyrus (including Broca’s area), the anterior insula and ventral premotor cortex, with critical contributions from connecting white-matter pathways such as the frontal aslant tract and arcuate fasciculus. In progressive forms of AOS, neurodegenerative changes often draw in adjacent fronto-insular and basal ganglia structures, with distinct phonetic and prosodic subtypes linked to diverging patterns of tau pathology. In post-stroke AOS, focal lesions to the precentral gyrus of the insula and surrounding frontal operculum disrupt feedforward motor planning, while secondary diaschisis may affect bilateral premotor interactions. Advanced imaging modalities including diffusion tensor imaging (DTI), neurite orientation dispersion and density imaging (NODDI) and resting-state functional connectivity mapping have refined our understanding of microstructural and network-level alterations. These insights underpin more targeted rehabilitation approaches and inform prognostic biomarkers for recovery and disease progression.

Research from Nature Portfolio

Recent studies have elucidated the molecular and imaging signatures of primary progressive apraxia of speech. Longitudinal multimodal imaging of patients with autopsy-confirmed progressive AOS revealed that phonetic subtypes correlate with corticobasal degeneration, whereas prosodic subtypes align with progressive supranuclear palsy. Distinct patterns of cortical atrophy within the cortico-striatopallidonigral network and differential rates of decline were observed, underscoring the role of 4R-tau pathology in driving clinical heterogeneity. Biochemical analyses highlighted a lower tau H1 haplotype frequency in this cohort, while tau aggregation profiles proved similar across subtypes. These findings delineate subtype-specific neuroanatomical trajectories and support development of targeted 4R-tau therapies.

Apraxia of Speech Assessment and Neuroanatomical Correlates publication trend

The graph below shows the total number of articles in apraxia of speech assessment and neuroanatomical correlates across all publications each year (not limited to Nature Index journals).

Technical terms

Apraxia of Speech (AOS): A motor planning disorder impairing voluntary coordination of speech movements.

Progressive Apraxia of Speech (PPAOS): A neurodegenerative syndrome characterised by gradually worsening speech motor planning deficits.

Diffusion Tensor Imaging (DTI): An MRI technique that maps the directionality and integrity of white-matter tracts by measuring water diffusion.

Neurite Orientation Dispersion and Density Imaging (NODDI): An advanced diffusion MRI method that quantifies neurite density and orientation dispersion in brain tissue.

Functional Connectivity: A measure of temporal correlation between spatially distinct brain regions, often assessed with resting-state fMRI.

References

1. A molecular pathology, neurobiology, biochemical, genetic and neuroimaging study of progressive apraxia of speech. Nature Communications (2021).
2. Longitudinal changes in functional connectivity in speech motor networks in apraxia of speech after stroke. Frontiers in Neurology (2022).
3. Combined assessment of progressive apraxia of speech brain microstructure by diffusion tensor imaging tractography and multishell neurite orientation dispersion and density imaging. Brain and Behavior (2024).
4. A case of pure apraxia of speech after left hemisphere stroke: behavioral findings and neural correlates. Frontiers in Neurology (2023).
5. Assessment protocol for patients with acquired apraxia of speech. The Egyptian Journal of Otolaryngology (2017).