“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

Abstract

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.

Consensus Paper: Language and the Cerebellum: an Ongoing Enigma

“…Disruption of (hand)written output (agraphia) may be the result of acquired or developmental neurological damage to the language system itself affecting spelling skills (the central agraphias) or of motor or sensory impairments that primarily compromise the ability to correctly execute the manual production of letters (the peripheral agraphias) [190]. …”

“…Recent clinical and functional neuroimaging studies, however, indicate that the cerebellum may be crucially implicated in this network as well [190, 193–195]. By means of an fMRI study, Katanoda et al [195] showed involvement of the cerebellum in the general neural network of writing.…”

Mastication Dyspraxia: A Neurodevelopmental Disorder Reflecting Disruption of the Cerebellocerebral Network Involved in Planned Actions

“…As a result it is hypothesized that "mastication dyspraxia" may have to be considered to represent a distinct nosological entity within the group of the developmental dyspraxias following a disruption of the cerebello-cerebral network involved in planned actions [26,36].…”

Memory impairment following right cerebellar infarction: a case study

“…Kim et al reported amnesia syndrome following left anterior thalamic infarction, and the brain SPECT image revealed decreased uptake in the ipsilateral frontotemporoparietal cortex and contralateral cerebellum that caused by disconnection of the cerebello-thalamo-cortical pathways (Kim, Hong, & Roh, 1994). The phenomenon of cerebello-cerebral diaschisis was also shown in patients of posterior fossa syndrome, and the 99m Tc-Ethyl cysteinate dimer SPECT results showed decreased perfusion in the thalamus as well as an area of hypoperfusion in the vermis (Baillieux et al, 2006;Mariën et al, 2013). It is considered that disconnection of cerebello-thalamic tracts causes functional suppression of the left anterior thalamus.…”