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OHBM2022

Presenter: Valentina Pacella, CNRS Bordeaux Abstract: Introduction: The anarchic hand syndrome refers to an inability to control the movements of one's own hand, which acts as if it has a will of its own (1–3). The symptoms may differ depending on whether the brain lesion is anterior, posterior, callosal or subcortical, but the relative classifications are not conclusive (4). This study investigates the role of white matter disconnections in a stroke patient whose symptoms are inconsistent with the mapping of the lesion site. Methods: A repeated neuropsychological investigation (executed at 2 and 6 months after the lesion onset) was associated with a review of the literature on the topic to identify the frequency of various different symptoms relating to this syndrome. The assessment investigated 6 typologies of symptoms resulting from the revision of the literature (papers from 2016 to 2019 have been scrutinised, continuing the work from (4) that reviewed the papers until 2015; a total of 11 articles met the inclusion criteria) as being the most common in AHS: (i) purposeful or semi-purposeful AH movements; (ii) non-purposeful AH movements; (iii) uncontrolled bilateral hand movements; (iv) hand-related feelings; (v) disconnection symptoms and (vi) other AH-related symptoms. An additional neuropsychological battery thoroughly investigated a broad spectrum of cognitive functions. The grey matter lesion analysis has been performed on the patient's T1 image acquired at 5 months after stroke. The Tractotron package of the BCBToolkit software (5) allowed the indirect investigation of white matter disconnection probability. The diffusion-weighted images (48 diffusion gradient volumes, of which 6 volumes with no diffusion gradient (B0), b-value of 2000 s/mm2) have been used for the whole-brain tractography (damped Richardson-Lucy algorithm was applied for spherical deconvolutions, 1.5 fixed fibre response parameter, geometric damping parameter of 8, whole-brain streamline tractography via Euler algorithm with a 45° angle threshold of and a step size of 0.5 mm). Tracts with the highest probability of disconnection in Tractotron have been manually reconstructed and compared with their spared homologues in the contra-lesional hemisphere (6). Results: The neuropsychological results indicated that the patient displayed symptoms typical of frontal (magnetic apraxia and grasping (7)), posterior (sensory loss and levitation (8)) and callosal (lack of bimanual coordination, loss of manual dexterity (3)) lesions. However, the lesion analysis (Fig.1) revealed the involvement of posterior damage (i.e. right hemisphere parietal and occipital cortices) and the lesion of temporal and insular structures. The indirect investigation of the patient's damaged white matter tracts showed that the damage expanded beyond the areas of direct lesion, involving long fronto-parietal, fronto-occipital and temporo-occipital connections, the posterior body of the corpus callosum (Fig.2c), and short sensorimotor connections. The analyses of the diffusion-weighted imaging data (Fig.2) confirmed the results and made it possible to identify the specific tracts which were disconnected. Thus, the patient's symptoms were associated with structures that, although not directly damaged, were dysfunctional due to a disconnection in their networks. Conclusions: The anarchic hand syndrome may be considered as a disconnection syndrome involving the integration of multiple antero-posterior, insular and interhemispheric networks. In order to comprehend this rare syndrome better, the clinical and neuroimaging data of rare single cases such as that here analysed, need to be integrated with the clinical reports available in the literature on this topic.