Arnold–Chiari Malformation, also referred to as Chiari Type II malformation, is a congenital neurological disorder in which not only the cerebellum but also the brainstem extend downward into the spinal canal through the foramen magnum.
Unlike Chiari Type I, which often develops later in adolescence or adulthood, Arnold–Chiari malformation is usually present at birth and strongly associated with spina bifida (particularly myelomeningocele). The condition disrupts the normal circulation of cerebrospinal fluid (CSF), leading to complications such as hydrocephalus, brainstem compression, and significant neurological deficits.
Causes of Arnold–Chiari Malformation
While the precise cause remains unclear, several factors play a role:
Abnormal development of the brain and skull during pregnancy.
Genetic predisposition to neural tube defects.
Strong association with spina bifida, especially myelomeningocele.
Impaired circulation of CSF during fetal development.
Symptoms of Arnold–Chiari Malformation
Clinical features typically appear at birth or shortly after. Common signs and symptoms include:
Breathing difficulties and swallowing problems in newborns.
Weak or abnormal cry, feeding difficulties, choking episodes.
Arm weakness and abnormal reflexes.
Hydrocephalus (excess fluid in the brain).
Seizures (rare but possible).
Developmental delays and impaired motor function.
In some patients, syringomyelia may occur, where fluid-filled cavities develop inside the spinal cord, causing progressive weakness, numbness, and sensory loss.
Diagnosis
Arnold–Chiari malformation is often identified during infancy or even before birth:
Prenatal ultrasound: Can reveal structural abnormalities during pregnancy.
Magnetic Resonance Imaging (MRI): The most reliable tool, providing a clear view of cerebellar and brainstem herniation.
Computed Tomography (CT): Useful for evaluating skull and spine bone structures.
Neurological examination: Detects motor and sensory dysfunctions.
Treatment for Arnold–Chiari Malformation
Therapy is tailored according to severity and associated conditions:
Monitoring: Mild cases without severe complications may only require regular observation.
Shunt placement: In patients with hydrocephalus, a ventriculoperitoneal shunt may be placed to divert excess CSF.
Posterior fossa decompression surgery (with or without duroplasty): Expands space at the skull base, relieving pressure on the cerebellum and brainstem, and restoring CSF flow.
Multidisciplinary care: Collaboration between neurosurgeons, neurologists, pediatricians, and physiotherapists ensures comprehensive management.
Conclusion
Arnold–Chiari malformation is a complex congenital disorder that requires early recognition and specialized treatment. Identifying complications such as hydrocephalus and syringomyelia in time plays a key role in improving quality of life. Advances in imaging and surgical techniques have greatly enhanced outcomes for affected children.