"Whole Brain Connectivity in Idiopathic Childhood Apraxia of Speech and the Effects of PROMPT Treatment: A Pilot Open Study."
Investigators: A.M. Chilosi, I.Podda, S. Fiori
IRCCS, Stella Maris Foundation, Pisa, Italy
Projected Supported by the PROMPT Institute
Rationale and Purpose of Research
Idiopathic apraxia of speech (CAS) can be present as the only symptom in otherwise healty children, thus occurring as a neurogenic speech sound disorder. In general, studies of CAS have not provided unequivocal information on aetiology and neural correlates of the disorder. Moreover, neuroanatomical and neurophysiopathological models of acquired adult apraxia of speech do not apply to children. Using the D.I.V.A model developed by Guenther et al (1995, 2001, 2006) , Terband et al (2009) carried out a series of simulations of imitative learning in CAS and hypothesized that the speech production system in CAS suffers from impaired auditory-motor integration and lacks feedforward anticipatory motor control.With regard to neuroanatomical correlates of idiopathic CAS, the few published MRI studies have not revealed any macrostructural brain abnormalities.
It has been hyphothesized that brain alterations associated with idiopathic CAS may be too subtle to be detected with standard clinical MRI sequencing methods, suggesting that more sensitive tecnhiques of analysis are necessary to determine the neural basis of the disorder. Among new advanced non-invasive MR techniques, Diffusion Tensor Imaging (DTI) enables investigation of the neural structural organization and developmental changes of white matter (WM) fibre tracts across ages (Baldoli et al 2014). This method could be particularly suitable to investigate the connectivity of somatosensory (tactile, kinesthetic and proprioceptive), auditory and motor circuitries subserving speech in CAS, and their possible changes after an appropriate targeted intervention.
Preliminary results of a pilot Diffusion MRI (dMRI) study (Fiori et al in preparation) conducted by our group on 18 children with CAS, revealed that several brain networks showed disrupted connectivity (lower fractional anisotropy, FA) in the CAS group compared to normal controls (p<0.05). Altered structural connectivity mainly involved supplementary motor areas (right>left) and the superior and middle temporal gyri (left> right), (see figure).
On the basis of this evidence, a first aim of the present project is to extend the structural connectome analysis to other children with CAS by using a High Angular Resolution Diffusion Imaging (HARDI) techinque. The choice of the HARDI technique was determined by the fact that it allows a detailed reconstruction of white matter connectivity by improving the resolution of multiple fibres orientation in a voxel. Moreover, one of our researchers has developed specific expertise in this method that has been proven effective in our pilot study.
With regard to treatment of the disorder, there is a growing evidence that PROMPT (Prompts for Restructuring Oral Muscular Phonetic Targets), can be effective in improving most of the main symptoms of CAS and may also induce structural modifications at the cortical level (see Kadis et al 2013). PROMPT, as a holistic, multimodal intervention system for motor speech disorders, is consistent with the evidence that speech motor learning and control require a systematic processing of auditory, tactile, kynesthetic, proprioceptive and visual information in order to achieve what eventually appears to be the most complex and integrated result of human movement (i.e. Bouchard et al., 2011, Hickok, 2009, Dhanjal et al., 2008).