Neuronal Migration Disorders

Neuronal migration disorders (NMDs) are a group of birth defects caused by the abnormal migration of neurons (nerve cells) in the developing brain and nervous system. Types of NMDs include:

• Agenesis of the corpus callosum: The tissue connecting the left and right sides of the brain is partially or completely missing.
• Agenesis of the cranial nerves: The nerves that lead from the brain to various parts of the head, neck, and trunk are partially or completely missing. 
• Argyria/lissencephaly: Absent or abnormally broad gyri in the cerebral hemispheres. Also known as lissencephaly, or “smooth brain.”
• Microgyria: The occurrence of abnormally small folds of the brain.
• Neuronal heterotopias (including band heterotopia): Gray matter appears in abnormal places in the brain, including around ventricles, in areas of white matter, or the fluid-filled spaces of the brain.
• Polymicrogyria: An abnormal number of small brain folds.
• Porencephaly: An abnormal fluid-filled cyst.
• Schizencephaly: A cleft or slit in the brain.

Neuronal migration disorders are genetic defects that are typically passed on from parent to child, though they also occur sporadically. Neuronal precursor cells change direction from a typical migration mode as they move from the ventricles into the cortex. This results in malformations of the cerebral hemispheres.

These disorders result from genetic defects passed from parent to child. Prenatal exposure to environmental stress and inflammation, as well as use of alcohol and drugs.

Neuronal migration disorders (NMDs) can be diagnosed using a prenatal ultrasound. Further detection is possible by running a fetal magnetic resonance imaging (MRI) scan. The latter can help provide more details on how severe the malformations are.

Some disorders have characteristic facial or skull features that can be recognized by a neurologist. Several genetic abnormalities in children with neuronal migration disorders (NMDs) have been identified, but the role they play in the development of these disorders is not yet well understood.

Symptoms vary, but often include:

• Poor muscle tone and motor function
• Seizures
• Developmental delays
• Impaired cognitive development
• Failure to grow and thrive
• Difficulties with feeding
• Swelling in the extremities
• A small head

Diagnosis of neuronal migration disorders can be determined through an MRI scan, with further information available through an EEG (which measures any present seizure activity) or muscle tone measurements using an EMG.

Treatment is symptomatic and may include antiseizure medication and special or supplemental education consisting of physical, occupational and speech therapies.

Daily life of those diagnosed with NMDs typically involves taking prescribed medication (usually an anti-seizure medicine). Additionally, working with a team of physical, occupational and speech therapists can help with symptoms.

To further your understanding of your diagnosis and to contribute to cutting-edge research, consider participating in a clinical trial so clinicians and scientists can learn more about causes, symptoms, treatment and prevention. Clinical research uses human volunteers to help researchers learn more about a disorder and perhaps find better ways to safely detect, treat or prevent disease.

All types of volunteers are needed—those who are healthy or may have an illness or disease—of all different ages, sexes, races and ethnicities to ensure that study results apply to as many people as possible, and that treatments will be safe and effective for everyone who will use them.

For information about participating in clinical research, visit NIH Clinical Research Trials and You. Learn about clinical trials currently looking for participants at Clinicaltrials.gov.