“Apraxic dysgraphia” in a 15-Year-Old Left-Handed Patient: Disruption of the Cerebello-Cerebral Network Involved in the Planning and Execution of Graphomotor Movements
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- Mariën, P., de Smet, E., de Smet, H.J. et al. Cerebellum (2013) 12: 131. doi:10.1007/s12311-012-0395-1
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Apraxic agraphia is a peripheral writing disorder caused by neurological damage. It induces a lack or loss of access to the motor engrams that plan and programme the graphomotor movements necessary to produce written output. The neural network subserving handwriting includes the superior parietal region, the dorsolateral and medial premotor cortex and the thalamus of the dominant hemisphere. Recent studies indicate that the cerebellum may be involved as well. To the best of our knowledge, apraxic agraphia has not been described on a developmental basis. This paper reports the clinical, neurocognitive and (functional) neuroimaging findings of a 15-year-old left-handed patient with an isolated, non-progressive developmental handwriting disorder consistent with a diagnosis of "apraxic dysgraphia". Gross motor coordination problems were objectified as well but no signs of cerebellar, sensorimotor or extrapyramidal dysfunction of the writing limb were found to explain the apraxic phenomena. Brain MRI revealed no supra- and infratentorial damage but quantified Tc-99m-ECD SPECT disclosed decreased perfusion in the anatomoclinically suspected prefrontal and cerebellar brain regions crucially involved in the planning and execution of skilled motor actions. This pattern of functional depression seems to support the hypothesis that "apraxic dysgraphia" might reflect incomplete maturation of the cerebello-cerebral network involved in handwriting. In addition, it is hypothesized that “apraxic dysgraphia” may have to be considered to represent a distinct nosological category within the group of the developmental dyspraxias following dysfunction of the cerebello-cerebral network involved in planned actions.