Developmental Coordination Disorder (Dyspraxia)

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Overview of Developmental Coordination Disorder

Developmental Coordination Disorder (DCD), or dyspraxia, is a neurodevelopmental disorder characterized by poor motor coordination and difficulty learning motor skills in an otherwise healthy child with a normal gross neurological examination. This condition may negatively impact the child’s life by interfering with socialization and academic performance. Additionally, DCD can lead to executive function deficits, preventing effective learning in early childhood education. Children with DCD experience difficulty executing coordinated motor actions accurately. The patients' movements may be slow and inaccurate. DCD manifests as mild fine and gross motor delays in childhood that are later attributed to motor learning difficulties.

Handwriting and Its Importance in Diagnosing Developmental Coordination Disorder

Handwriting is a complex skill, encompassing subtasks that include idea organization, phrase structure, spelling, grammar, memory, vocabulary, planning, revision, and the writing motor act. When attention is focused on maintaining concentration, handwriting becomes laborious, leading to a decline in the quality of written compositions. Individuals with DCD can write fewer words per minute than people without DCD. Many models have been introduced to analyze handwriting difficulties in DCD. Van Galen's model stands out as it uniquely integrates handwriting's cognitive, linguistic, and biomechanical aspects.

The first handwriting stage requires the writer’s motivation, which activates the intention to write. The semantic retrieval stage, wherein the writer develops ideas from vocabulary, occurs next. In this phase, the writer elaborates on what to write and retrieves semantic information before initiating the motor-writing task on paper. Syntactical construction is performed afterward. These 3 premotor stages are the biggest factors impacting the handwriting speed, or the number of words produced per minute, of children with DCD.

Spelling is the first phase of motor planning, and it consists of matching the phoneme, the letter's sound, with the grapheme, the symbol that represents a phoneme. The allograph selection stage occurs when the match is complete. Longer words require a longer time to convert phonemes into graphemes. Thus, individuals with DCD tend to show significant difficulty with words composed of 2 or more syllables.

Muscular adjustment is the last stage, and it occurs when the signal travels from the brain to the hand. Individuals with DCD struggle with controlling spacing and the letters' sizes and alignment, which may affect the text's legibility. Up to 95% of children with DCD have handwriting difficulties, and 57% demonstrate decreased legibility, writing speed, and letter formation quality as compared to their peers.

Functional Regions of the Cerebral Cortex

Different cortical areas are associated with specific functions (see Image. Brodmann Cytoarchitectonic Designations). The primary sensory and motor areas comprise 10% of the cortex, while the rest is composed of the association cortex. The forebrain's most widely studied functional regions are described in the table below.

CDC arises from aberrant processes in various parts of the cerebral cortex. Cerebellar abnormalities have also been implicated, particularly structural variations like gray matter volume changes and altered activation patterns.[38]