Verbal Adynamia and Conceptualization in Partial Rhombencephalosynapsis and Corpus Callosum Dysgenesis.

Verbal adynamia is characterized by markedly reduced spontaneous speech that is not attributable to a core language deficit such as impaired naming, reading, repetition, or comprehension. In some cases, verbal adynamia is severe enough to be considered dynamic aphasia. We report the case of a 40-year-old, left-handed, male native English speaker who presented with partial rhombencephalosynapsis, corpus callosum dysgenesis, and a language profile that is consistent with verbal adynamia, or subclinical dynamic aphasia, possibly underpinned by difficulties selecting and generating ideas for expression. This case is only the second investigation of dynamic aphasia in an individual with a congenital brain malformation. It is also the first detailed neuropsychological report of an adult with partial rhombencephalosynapsis and corpus callosum dysgenesis, and the only known case of superior intellectual abilities in this context.

Callosal agenesis and congenital mirror movements: outcomes associated with DCC mutations.

Pathogenic variants in the gene encoding deleted in colorectal cancer (DCC) are the first genetic cause of isolated agenesis of the corpus callosum (ACC). Here we present the detailed neurological, brain magnetic resonance imaging (MRI), and neuropsychological characteristics of 12 individuals from three families with pathogenic variants in DCC (aged 8-50y), who showed ACC and mirror movements (n=5), mirror movements only (n=2), ACC only (n=3), or neither ACC nor mirror movements (n=2). There was heterogeneity in the neurological and neuroimaging features on brain MRI, and performance across neuropsychological domains ranged from extremely low (impaired) to within normal limits (average). Our findings show that ACC and/or mirror movements are associated with low functioning in select neuropsychological domains and a DCC pathogenic variant alone is not sufficient to explain the disability. WHAT THIS PAPER ADDS: Neuropsychological impairment severity is related to presence of mirror movements and/or agenesis of the corpus callosum. A DCC pathogenic variant in isolation is associated with the best prognosis.

Mirror movements and callosal dysgenesis in a family with a DCC mutation: Neuropsychological and neuroimaging outcomes.

Corpus callosum dysgenesis is a congenital abnormality whereby the corpus callosum fails to develop normally, and has been associated with a range of neuropsychological outcomes. One specific finding in some individuals with corpus callosum dysgenesis is "congenital mirror movement disorder", which is the presence of involuntary movements on one side of the body that mimic voluntary movements of the other side. Mirror movements have also been associated with mutations in the deleted in colorectal carcinoma (DCC) gene. The current study aims to comprehensively document the neuropsychological outcomes and neuroanatomical mapping of a family (a mother, daughter and son) with known DCC mutations. All three family members experience mirror movements, and the son additionally has partial agenesis of the corpus callosum (pACC). All family members underwent extensive neuropsychological testing, spanning general intellectual functioning, memory, language, literacy, numeracy, psychomotor speed, visuospatial perception, praxis and motor functioning, executive functioning, attention, verbal/nonverbal fluency, and social cognition. The mother and daughter had impaired memory for faces, and reduced spontaneous speech, and the daughter demonstrated scattered impairments in attention and executive functioning, but their neuropsychological abilities were largely within normal limits. By contrast, the son showed areas of significant impairment across multiple domains including reduced psychomotor speed, fine motor dexterity and general intellectual functioning, and he was profoundly impaired across areas of executive functioning and attention. Reductions in his verbal/non-verbal fluency, with relatively intact core language, resembled dynamic frontal aphasia. His relative strengths included aspects of memory and he demonstrated largely sound theory of mind. Neuroimaging revealed an asymmetric sigmoid bundle in the son, connecting, via the callosal remnant, the left frontal cortex with contralateral parieto-occipital cortex. Overall, this study documents a range of neuropsychological and neuroanatomical outcomes within one family with DCC mutations and mirror movements, including one with more severe consequences and pACC.