The c.429_452 duplication of the ARX gene: a unique developmental-model of limb kinetic apraxia:

BACKGROUND: The c.429_452dup24 of the ARX gene is a rare genetic anomaly, leading to X-Linked Intellectual Disability without brain malformation. While in certain cases c.429_452dup24 has been associated with specific clinical patterns such as Partington syndrome, the consequence of this mutation has been also often classified as "non-specific Intellectual Disability". The present work aims at a more precise description of the clinical features linked to the c.429_452dup24 mutation. METHODS: We clinically reviewed all affected patients identified in France over a five-year period, i.e. 27 patients from 12 different families. Detailed cognitive, behavioural, and motor evaluation, as well as standardized videotaped assessments of oro-lingual and gestural praxis, were performed. In a sub-group of 13 ARX patients, kinematic and MRI studies were further accomplished to better characterize the motor impairment prevalent in the ARX patients group. To ensure that data were specific to the ARX gene mutation and did not result from low-cognitive functioning per se, a group of 27 age- and IQ-matched Down syndrome patients served as control. RESULTS: Neuropsychological and motor assessment indicated that the c.429_452dup24 mutation constitutes a recognizable clinical syndrome: ARX patients exhibiting Intellectual Disability, without primary motor impairment, but with a very specific upper limb distal motor apraxia associated with a pathognomonic hand-grip. Patients affected with the so-called Partington syndrome, which involves major hand dystonia and orolingual apraxia, exhibit the most severe symptoms of the disorder. The particular "reach and grip" impairment which was observed in all ARX patients, but not in Down syndrome patients, was further characterized by the kinematic data: (i) loss of preference for the index finger when gripping an object, (ii) major impairment of fourth finger deftness, and (iii) a lack of pronation movements. This lack of distal movement coordination exhibited by ARX patients is associated with the loss of independent digital dexterity and is similar to the distortion of individual finger movements and posture observed in Limb Kinetic Apraxia. CONCLUSION: These findings suggest that the ARX c.429_452dup24 mutation may be a developmental model for Limb Kinetic Apraxia

Pour une approche psychosociale des instruments de gestion et d’organisation du travail

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Techniques, méthodes et démarches d’évaluation des aides techniques

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Apomorphine-induced inhibition of substantia nigra dopamine neurons: Effects of unilateral injection through the internal carotid artery

International audiencePossible indirect components in the inhibition of firing of A9 dopamine neurons induced by systemic apomorphine were studied using unilateral drug administration through the internal carotid artery, known to irrigate only the ipsilateral mid- and forebrain. When compared to intravenous injection, unilateral intracarotid administration inhibited ipsilateral neurons with a marked decrease of both the latency (less than 1 s) and the dose required for complete inhibition, whereas contralateral neurons were not affected. This suggests a first-pass central effect of apomorphine, presumably associated with brain extraction. Thus, peripheral and hindbrain targets do not seem to contribute to the inhibitory effect of low doses of systemic apomorphine. An intranigral possible mode of action is discussed in view of the particular arrangement of dopaminergic dendrites within the zona reticulata

Nouvelles pratiques de travail : innovations technologiques, changements organisationnels

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Usage des TIC et évolutions des pratiques socioprofessionnelles des cadres : quels repères pour le métier et quelles incidences sur la santé ?

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Conditions de travail, évaluation des risques et management de la sécurité

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