Neuronal Migration Disorders - Causes, Symptoms, and Treatment

What Are Neuronal Migration Disorders?

A group of birth defects known as neuronal migration disorders (NMDs) is caused by aberrant neuronal migration in the developing nervous system and brain. Physiologically, neurons must move from the regions of the growing brain where they are made to the regions where they will establish their correct neural circuits. A complicated network of chemical cues signals neuronal migration, which can start as early as the second month of pregnancy. Neurons do not reach where they should when all these signals are missing or wrong. This can cause the cerebral hemispheres, cerebellum, brainstem, or hippocampus to have structurally altered or missing parts. Schizencephaly (clefts in the cerebral hemisphere), porencephaly (development of cerebrospinal fluid-filled cavities in the brain), lissencephaly (absence of brain convolutions), agyria (absence of gyri on brain surface), macrogyria (large and fewer gyri on the brain), polymicrogyria (the folds in the brain are extremely tiny and form in an excessive number), pachygyria (presence of broad, flat, and fewer gyri in the brain), microgyria (occurrence of small gyri in the brain), micropolygyria, neuronal heterotopias (brain disorder occurring due to lack of neural migration), corpus callosum agenesis (complete or partial absence of the nerves connecting the left and right side of the brain), and cranial nerves agenesis (complete or partial absence of the cranial nerve) are among the anatomical abnormalities seen in neuronal migration disorders.

What Are the Other Conditions Associated With Neuronal Migration Disorders?

Neuronal migration disorders may also be present in conjunction with other brain development disorders. These conditions may include the following:

• Chiari Malformation: In this condition, the spinal canal is invaded by the brain's bottom portion. Some patients with Chiari malformation are asymptomatic.

• Dandy-Walker Syndrome: The cerebellum, a region of the brain, does not properly form in people with this disorder.

• Holoprosencephaly: The brain's two halves do not divide as they should in this condition.

• Hydrocephalus: The fluid that surrounds the brain accumulates abnormally in this disease. This results in increased cerebral pressure.

• Spina Bifida: This condition is characterized by improper development of the spine.

What Causes Neuronal Migration Disorders?

According to doctors, neuronal migration diseases are genetic, meaning a defective gene prevents the neural circuits from developing normally. While certain neural migration abnormalities are hereditary or passed down from parents to children, most appear to result from random genetic mutations. Neuronal migration disorders have been linked to mutations in genes related to neural migration, yet it is unclear how these mutations contribute to the onset of these disorders. It has been discovered that abnormal neural migration can cause more than 25 different neural migration disorders.

What Are the Symptoms of Neuronal Migration Disorders?

The neuronal migration disorder indications and symptoms vary according to the part of the brain affected and the degree of abnormalities. Neuronal migration disorders may not show signs at birth; instead, they become more visible as the infant fails to develop and grow normally. Common symptoms of neuronal migration disorders are:

• Failure to achieve developmental milestones and developmental delay in children.

• Loss of muscle tone and movement problems.

• Failure to thrive.

• Learning disabilities.

• Poor motor functioning.

• Seizures.

• Impaired cognitive development.

• Inability to feed properly.

• Mental retardation.

• Swelling in the limbs and extremities.

• The smaller size of the head.

• The majority of newborns with neuronal migration disorders seem normal; however, some conditions have distinguishing features of the face or skull that a neurologist can spot.

How Are Neuronal Migration Disorders Diagnosed?

Neuronal migration disorders can be diagnosed in the following ways:

• Brain Imaging Test: An MRI (magnetic resonance imaging) scan helps diagnose the majority of neuronal migration abnormalities because it reveals the typical pattern of missing or abnormal brain tissue. The highest image quality is offered by MRI (magnetic resonance imaging). Therefore, it is the ideal diagnostic tool. Before birth, a diagnosis can be made via fetal MRI as well. Neuronal migration disorders in newborns and children can be diagnosed with CT (computed tomography) scans. Ultrasounds can also be done to diagnose neuronal migration disorders in infants.

• Genetic Testing: Finding out if a neuronal migration disorder has a genetic etiology may be possible with genetic testing. Genetic testing is also helpful in determining any risk of further complications. A few examples of suggested genetic tests are; chromosomal microassay, brain malformation panel, whole exome sequencing, etc.

• Electroencephalograms: An electroencephalogram (EEG) can be used to determine seizure activity in the brain.

• Electromyogram: An electromyogram (EMG) is done to measure muscle tone.

• Other Tests: Different blood and urine tests could be advised. These tests could aid in the investigation of further NMD-related issues. These tests can be done to check for malnutrition as well.

How Are Neuronal Migration Disorders Treated?

Although there is no way to replace damaged or missing brain tissue, many things can be done to alleviate the symptoms of neuronal migration disorder. Professionals, such as physiotherapists, occupational therapists, speech or language therapists, and others, will be required to treat children with neuronal migration disorders.

• Medications: Medications can treat seizures, stiffness, atypical muscular movements, breathing issues, sleep issues, drooling, constipation, hormonal problems, urinary tract infections, etc. These are common problems associated with neuronal migration disorders.

• Surgery: Individuals with serious symptoms are frequently advised of surgery. Surgery may be helpful in the placement of a feeding tube, excess muscle tightness, hydrocephalus (fluid buildup in the brain), seizures that are unresponsive to medications, scoliosis (sideways curvature of the spine), and hearing and vision problems.

• Physical and Occupational Therapy: Physical and occupational therapy may be useful in developing motor skills, improving muscle stiffness, and increasing flexibility.

• Speech Therapy: Speech and swallowing therapy are useful in effective communication and safe eating.

There is no definitive cure for neuronal migration disorders. However, timely and consistent therapy may be extremely helpful in certain cases. Some kids will require regular medication to manage other issues and avoid seizures. A feeding tube will also help certain kids who need more nutrition. A shunt operation might be required to reduce head pressure when hydrocephalus is present.

Conclusion:

The prognosis for children with neuronal migration disorders varies greatly depending on the degree of the disorder and the part of the brain that is defective or absent. While some children may just have minor disabilities, others will require more comprehensive support. The presence of neurological signs and symptoms also greatly affects the prognosis. However, more research is still going on to understand these disorders better and prevent the development of neuronal migration disorders. The information obtained from this research lays the groundwork for comprehending abnormal development and offers possibilities for fresh approaches to treating and preventing illnesses associated with improper neural migration.