Abstract
The acquisition and evolution of speech production, discourse and communication can be negatively impacted by brain malformations. We describe, for the first time, a case of developmental dynamic dysphasia (DDD) in a right-handed adolescent boy (subject D) with cortical malformations involving language-eloquent regions (inferior frontal gyrus) in both the left and the right hemispheres. Language evaluation revealed a markedly reduced verbal output affecting phonemic and semantic fluency, phrase and sentence generation and verbal communication in everyday life. Auditory comprehension, repetition, naming, reading and spelling were relatively preserved, but executive function was impaired. Multimodal neuroimaging showed a malformed cerebral cortex with atypical configuration and placement of white matter tracts bilaterally and abnormal callosal fibers. Dichotic listening showed right hemisphere dominance for language, and functional magnetic resonance imaging (fMRI) additionally revealed dissociated hemispheric language representation with right frontal activation for phonology and bilateral dominance for semantic processing. Moreover, subject D also had congenital mirror movements (CMM), defined as involuntary movements of one side of the body that mirror intentional movements of the other side. Transcranial magnetic stimulation and fMRI during voluntary unimanual (left and right) hand movements showed bilateral motor cortex recruitment and tractography revealed a lack of decussation of bilateral corticospinal tracts. Genetic testing aimed to detect mutations that disrupt the development of commissural tracts correlating with CMM (e.g., Germline DCC mutations) was negative. Overall, our findings suggest that DDD in subject D resulted from the underdevelopment of the left inferior frontal gyrus with limited capacity for plastic reorganization by its homologous counterpart in the right hemisphere. Corpus callosum anomalies probably contributed to hinder interhemispheric connectivity necessary to compensate language and communication deficits after left frontal involvement.
Highlights
Children and adults with language and literacy impairments tend to have weaker cerebral lateralization than neurotypically developing individuals (de Guibert et al, 2011; Bishop, 2013; Ogawa et al, 2019)
Memory was examined with the Test of Memory and Learning (TOMAL) (Reynolds and Bigler, 1994) and executive functions were tested with the Trail-Making Test (TMT) (Reitan, 1958; ArangoLasprilla et al, 2017), the Hayling Sentence Completion Test (HSCT) (Burgess and Shallice, 1997; Abusamra et al, 2007; Cartoceti et al, 2008), the Wisconsin Card Sorting Test (WCST) (Grant and Berg, 1948; Heaton et al, 2009) and the Stroop Test (Stroop, 1935)
On the Wechsler Intelligence Scale for Children (WISC), subject D performed in the inferior range in all three intellectual quotient (IQ) scores and his performance was impaired on the Raven Colored Progressive Matrices (RCPM)
Summary
Children and adults with language and literacy impairments (specific language impairment, dyslexia, and autism spectrum disorders) tend to have weaker cerebral lateralization than neurotypically developing individuals (de Guibert et al, 2011; Bishop, 2013; Ogawa et al, 2019). The presence of long-lasting deficits is the rule in specific language impairments and this has been related to bilateral brain abnormalities (Vargha-Khadem et al, 1998; Guerreiro et al, 2002; Rapin et al, 2003; SorianoMas et al, 2009). In this respect, there is evidence of how multiple brain systems may sustain the same function (e.g., degeneracy – Noppeney et al, 2004; Stefaniak et al, 2019), which may explain cases of resilience of language/cognitive functions to brain lesions. Neural adaptation may be less efficient in cases of bilateral brain abnormalities and might represent an earlier neural marker for developmental language disorders by interfering with the continuous acquisition of skillful language functions (discourse, functional communication)
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