Isolated corpus callosum agenesis

Isolated corpus callosum agenesis (also known as isolated agenesis of the corpus callosum, or isolated ACC) is a rare congenital brain malformation characterized by the partial or complete absence of the corpus callosum — the major bundle of nerve fibers that connects the left and right hemispheres of the brain. Unlike syndromic forms of corpus callosum agenesis, the isolated form occurs without other major associated malformations or as part of a recognized genetic syndrome. The corpus callosum normally plays a critical role in interhemispheric communication, coordinating motor, sensory, and cognitive functions between the two sides of the brain. Clinical presentation is highly variable. Some individuals with isolated ACC may be entirely asymptomatic and discovered incidentally on brain imaging. Others may present with developmental delay, intellectual disability (often mild), learning difficulties, speech and language delays, seizures, and difficulties with complex problem-solving or social cognition. Motor coordination problems and challenges with tasks requiring interhemispheric transfer of information (such as bimanual coordination) may also occur. The condition can be detected prenatally via ultrasound or fetal MRI, or postnatally through neuroimaging prompted by developmental concerns. The etiology of isolated ACC is heterogeneous and may involve genetic factors, though in many cases the cause remains unknown. Both autosomal dominant and autosomal recessive inheritance patterns have been described in familial cases, and de novo mutations may also occur. There is no cure or specific treatment for isolated ACC. Management is supportive and individualized, focusing on early intervention services, speech therapy, occupational therapy, physical therapy, and educational support as needed. Seizures, when present, are managed with standard antiepileptic medications. Prognosis varies widely, with many individuals leading independent lives, particularly when cognitive impairment is mild or absent.

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