What Happens if the Corpus Callosum Is Damaged
Damage to any part of the corpus callosum can lead to distorted or absent communication between the left and right hemispheres of the brain

The function of the corpus callosum is to connect the two halves of the brain. Damage to any part of the corpus callosum can lead to distorted or absent communication between the left and right hemispheres of the brain.

Disorders caused by callosal damage include:

Pseudobulbar palsy

Most of the muscles in the face are controlled by the brain stem, and these signals must pass through the corpus callosum for interhemispheric coordination. Therefore, problems related to facial movement can arise if the corpus callosum becomes damaged. The person loses control over facial muscles and makes strange facial expressions.

Speech and movement ataxia

Each hemisphere of the brain controls the opposite side of the body. The brain must coordinate movements with both sides for appropriate motor responses, and this coordination is mediated by the corpus callosum. If the corpus callosum is injured, the signal transmission from one hemisphere to the other is impaired and can lead to serious coordination problems, or ataxia. The person lacks control or coordination of voluntary movements such as:

  • Walking
  • Picking up objects
  • Speaking
  • Moving eyes
  • Swallowing

Alien hand syndrome

Alien hand syndrome is one of the strangest symptoms of corpus callosum damage. It most commonly affects the left hand but can involve the right hand too in some cases. It causes the hand to move and act on its own without any cognitive control or awareness from the person, and the person cannot perform goal-oriented tasks.

Agenesis of corpus callosum

Corpus callosum agenesis is a congenital defect in which neuronal fiber connection is either partially or completely not formed. It is caused by disruption of the development of the fetal brain. This most commonly is the result of: 

  • Chromosome errors
  • Genetic factors such as Andermann or Aicardi syndrome
  • Prenatal infections such as rubella 
  • Other factors related to pregnancy and prenatal environment

What learning and developmental issues are caused by corpus callosum damage?

Children with corpus callosum diseases have a wide range of learning disabilities and limitations. Severity depends on the number of structural issues in the brain and the existence of additional syndromes. Some kids have minor learning difficulties, whereas others have significant intellectual impairment. Impaired cognitive abilities are frequently accompanied by other developmental disabilities. 

The more abnormalities a child has with their brain structure, the more likely they are to have delayed speech, motor skills, and social skills. Some children who perform well in school may have “hidden” learning difficulties. Specialized evaluation of these children’s learning strengths and weaknesses will be critical to their development.

The following symptoms are typical in children with primary corpus callosum issues (without accompanying syndromes or problems with brain formation):

  • Learning difficulties caused by cognitive disorders such as intellectual disability
  • Problems with problem solving and abstract thinking
  • Poor motor coordination
  • Low muscle tone
  • Attention deficit hyperactivity disorder
  • Immaturity in social situations

QUESTION

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What is the anatomy of the corpus callosum?

The corpus callosum is structurally composed of four types of fibers known as commissural fibers, divided from anterior (front) to posterior (back) into:

  • Rostrum
  • Genu
  • Body/trunk 
  • Splenium

The corpus callosum is the primary commissural region of the brain that stretches across the midline and connects the same cortical areas in the right and left hemispheres. The fibers connecting the two cerebral hemispheres to one other form a brain structure that is visible on gross examination. 

The length of the corpus callosum ranges about 10 cm with 200 to 300 million heavily myelinated axonal projections (neurons whose axons extend from the neuronal cell body within the central nervous system).

The primary function of the corpus callosum is to integrate information and process motor, sensory, and higher cognitive signals between our brain's two hemispheres. 

Damage to the corpus callosum may result in cognitive and physical deficits. In most cases, injuries to the corpus callosum will resolve after a few months as the injury heals, but in some cases, the injury may be more serious.

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Medically Reviewed on 11/23/2021
References
Image Source: iStock Images

https://neuro.psychiatryonline.org/doi/10.1176/appi.neuropsych.15070159

https://www.jstage.jst.go.jp/article/nmc/48/1/48_1_1/_pdf

https://www.ncbi.nlm.nih.gov/books/NBK448209/