Brain Tractography
Diffusion Tractography of the human brain.

What is the corpus callosum?

The corpus callosum is the largest neural fiber tract in the brain. Consisting of approximately 190 million neurons, this structure bridges the left and right brain hemispheres and permits the exchange of high-speed communications across the brain.

The corpus callosum supports a wide variety of brain functions, ranging from the coordination of basic sensory and motor functions to passing information needed for a wide range of high-level cognitive processes involved in executive functions, social and emotional functions, planning, language and other functions.

What are disorders of corpus callosum?

Approximately one person in every 4000 is born with all or part of their corpus callosum missing. Collectively these conditions are referred to as disorders of the corpus callosum, or corpus callosum dysgenesis (CCD), however numerous subtypes exist. For example, in some cases people may be born without a corpus callosum entirely (agenesis of the corpus callosum, ACC) or with an unusually thin corpus callosum (hypoplasia).

While the corpus callosum is an integral part of the brain, it should be noted that is not required for a person’s survival; this is because the corpus callosum does not transmit information about essential life processes, such as a person’s breathing or heart rate. However, the absence of the corpus callosum, whether in part or in full, has been associated with a wide range of symptoms. These symptoms usually stem from the reduced ability of affected individuals to communicate complex information quickly and efficiently between the two sides of the brain.

How are disorders of corpus callosum diagnosed?

Malformations of the corpus callosum are diagnosed by a radiologist, based on how it appears on an ultrasound, computer tomography (CT), or magnetic resonance imaging (MRI) scan. The presence of common secondary features, such as an enlargement of the ventricular spaces, may assist in diagnosing an incidence of a callosal disorder. 

During routine prenatal ultrasound sessions, disorders of the corpus callosum can be detected as early as 20 weeks gestation. If diagnosed after birth, it is typically because an individual had had an CT or MRI scan for another, not necessarily related, reason.

What challenges do individuals with disorders of the callosum face?

The effects of CCD on an individual are wide ranging and can vary considerably between individuals. In some cases, individuals born with this condition never learn to walk or talk and require permanent full-time care for the rest of their lives. In others, the symptoms are quite mild, and have a minimal impact on day-to-day activities. Unfortunately, clinicians currently do not have the means to provide an accurate prognosis for individuals diagnosed with CCD, especially when diagnosed during fetal life.