Mastication dyspraxia: a neurodevelopmental disorder reflecting disruption of the cerebellocerebral network involved in planned actions

This paper reports the longitudinal clinical, neurocognitive, and neuroradiological findings in an adolescent patient with nonprogressive motor and cognitive disturbances consistent with a diagnosis of developmental coordination disorder (DCD). In addition to prototypical DCD, the development of mastication was severely impaired, while no evidence of swallowing apraxia, dysphagia, sensorimotor disturbances, abnormal tone, or impaired general cognition was found. He suffered from bronchopulmonary dysplasia and was ventilated as a newborn for 1.5 months. At the age of 3 months, a ventriculoperitoneal shunt was surgically installed because of obstructive hydrocephalus secondary to perinatal intraventricular bleeding. At the age of 5 years, the patient's attempts to masticate were characterized by rough, effortful, and laborious biting movements confined to the vertical plane. Solid food particles had a tendency to get struck in his mouth and there was constant spillage. As a substitute for mastication, he moved the unground food with his fingers in a lateral direction to the mandibular and maxillary vestibule to externally manipulate and squeeze the food between cheek and teeth with the palm of his hand. Once the food was sufficiently soft, the bolus was correctly transported by the tongue in posterior direction and normal deglutition took place. Repeat magnetic resonance imaging (MRI) during follow-up disclosed mild structural abnormalities as the sequelae of the perinatal intraventricular bleeding, but this could not explain impaired mastication behavior. Quantified Tc-99m-ethylcysteinate dimer single-photon emission computed tomography (Tc-99m-ECD SPECT), however, revealed decreased perfusion in the left cerebellar hemisphere, as well as in both inferior lateral frontal regions, both motor cortices, and the right anterior and lateral temporal areas. Anatomoclinical findings in this patient with DCD not only indicate that the functional integrity of the cerebellocerebral network is crucially important in the planning and execution of skilled actions, but also seem to show for the first time that mastication deficits may be of true apraxic origin. As a result, it is hypothesized that "mastication dyspraxia" may have to be considered as a distinct nosological entity within the group of the developmental dyspraxias following a disruption of the cerebellocerebral network involved in planned actions.