Agenesis of the Corpus Callosum (ACC) is a rare neurological condition. The Corpus Callosum is a bridge of white matter joining the two cerebral hemispheres of the brain. It forms during the course of brain development. The frequency with which it fails to form is normally not known as its total or partial absence can only be demonstrated with brain imaging procedures and these will usually only be performed if individuals have neurological abnormalities. Hence there may well be many asymptomatic individuals with partial or complete callosal agenesis.

Moreover, callosal agenesis may be and often is associated with other developmental brain anomalies and it is often these, rather than the callosal agenesis itself, which is the cause of subsequent neurological disability.

The clinical manifestations are best described under two headings: syndromic and non-syndromic.

Non-syndromic are more common and affected patients usually present with a large head, seizures and developmental delay. Hypertelorism (widely spaced eyes) occurs in many also. Seizure control may be difficult to achieve. Although the head can be very large ventricular shunting procedures for hydrocephalus are not indicated or helpful.

Many neurological syndromes also include agenesis of the corpus callosum. All of these have additional brain malformations and affected individuals are usually severely disabled often with dysmorphic characteristics and global developmental delay. Often associated with other midline cerebral and cranial abnormalities such as septo-optic dysplasia, it is sometimes associated with pituitary dysplasia. Because of this fits are sometimes due to hypoglycaemia (growth hormone and cortisol deficiency) as well as due to structural brain abnormality

Inheritance patterns
In the non-syndromic form of callosal agenesis genetic transmission is rare although there are a few autosomal recessive, X-linked and dominant cases on record. Genetic advice to affected individuals and their families can be helpful therefore. More frequently the non-syndromic form of callosal agenesis is an anomaly of brain development that is post conceptually determined, sometimes in association with chromosomal abnormalities.

In the syndromic form of callosal agenesis referral for precise neurological diagnosis is required. The majority of these syndromes do occur sporadically but these are occasional kindreds reported with familial incidence. Again dominant, X-linked and recessive disorders have been described whilst the Aicardi syndrome is thought to result from an X-linked dominant mutation.

Prenatal diagnosis
Agenesis of the Corpus Callosum is undetectable through routine prenatal tests. ACC may be detected with a scan at eighteen weeks.

Medical text written November 1998 by Dr L Rosenbloom. Last updated December 2001 by Dr L Rosenbloom. Last reviewed May 2005 by Dr L Rosenbloom, Consultant Paediatric Neurologist, Alder Hey Children's Hospital, Liverpool, UK.

Further Online Resources
Medical texts in The Contact a Family Directory are designed to give a short, clear description of specific conditions and rare disorders. More extensive information on this condition can be found on a range of reliable, validated web sites and links to them are included in the CD-ROM version of this Directory. Further information on these resources can be found in our Medical Information on the Internet article.

Corpal
20 Tollbar
Rushden
Northampton
NN10 6DP
Tel: 01933 386817
e-mail: accCorpal@yahoo.co.uk

CORPAL is a National Registered Charity No. 1086019, re-established in 1997. It offers support by telephone and letter and links families where possible. It publishes an occasional newsletter and has information available, details on request. Please send SAE. The organisation is in touch with over 270 families.

Group details last confirmed September 2007.