Agenesis of the corpus callosum

Agenesis of the Corpus Callosum (ACC) is a rare birth defect (congenital disorder) in which there is a complete or partial absence of the corpus callosum. Agenesis of the corpus callosum occurs when the corpus callosum, the band of tissue connecting the two hemispheres of the brain, does not develop typically in utero. In addition to agenesis of the corpus callosum, other callosal disorders include hypogenesis (partial formation), dysgenesis (malformation) of the corpus callosum, and hypoplasia (underdevelopment) of the corpus callosum. [1]

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Diagnosis

Callosal disorders can only be diagnosed through a brain scan. [2] They may be diagnosed through an MRI, CT Scan, prenatal ultrasound, or prenatal MRI. [3]

Cause

Agenesis of the Corpus Callosum is caused by disruption to development of the fetal brain between the 5th and 16th week of pregnancy.[4] In most cases, it is not possible to know what caused an individual to have ACC or another callosal disorder. However, research suggests that some possible causes may include chromosome errors, inherited genetic factors, prenatal infections or injuries, prenatal toxic exposures, structural blockage by cysts or other brain abnormalities, and metabolic disorders. [5]

Signs and symptoms

Signs and symptoms of Agenesis of the Corpus Callosum and other callosal disorders vary greatly among individuals. However, some characteristics common in individuals with callosal disorders include vision impairments, low muscle tone (hypotonia), poor motor coordination, delays in motor milestones such as sitting and walking, low perception of pain, delayed toilet training, chewing and swallowing difficulties, early speech and language delays, and social difficulties. Recent research suggests that specific social difficulties may be a result of impaired face processing.[6] Unusual social behavior in childhood is often mistaken for or misdiagnosed as Asperger's syndrome or other autism spectrum disorders. Other characteristics sometimes associated with callosal disorders include seizures, spasticity, early feeding difficulties and/or gastric reflux, hearing impairments, abnormal head and facial features, and mental retardation.[7]

Associated syndromes and conditions

Some syndromes that frequently include ACC are Aicardi syndrome, Andermann syndrome, Shapiro syndrome, Acrocallosal syndrome,septo-optic dysplasia, Mowat-Wilson syndrome and Menkes syndrome. Some conditions that are sometimes associated with ACC include maternal nutritional deficiencies or infections, metabolic disorders, Fetal alcohol syndrome, and orofacial abnormalities. [8]

Treatment

There are currently no specific medical treatments for callosal disorders, but individuals with ACC and other callosal disorders may benefit from a range of developmental therapies, educational support, and services. It is important to consult with a variety of medical, health, educational and social work professionals. Such professionals include neurologists, neuropsychologists, occupational therapists, physical therapists, speech-language pathologists, pediatricians, geneticists, special educators, early intervention specialists, and adult service providers. [9]

Prognosis

Prognosis varies depending on the type of callosal abnormality and associated conditions or syndromes. It is not possible for the corpus callosum to regenerate or degenerate (i.e., the corpus callosum will not regrow or diminish). [10]. Although some individuals with callosal disorders have average intelligence and lead normal lives, neuropsychological testing reveals subtle differences in higher cortical function compared to individuals of the same age and education without ACC.

Special cases

Kim Peek, inspiration for the film Rain Man, is famous for his savant abilities. Peek was born with agenesis of the corpus callosum, along with macrocephaly and damage to the cerebellum.