What is Arnold-Chiari?
Arnold-Chiari malformation (ACM), also known as Chiari malformation, is a structural defect in the brain in which the cerebellum, which is normally situated at the back of the skull, protrudes through an opening in the skull called the foramen magnum. The foramen magnum is the large opening at the base of the skull through which the spinal cord passes.
The cerebellum is responsible for coordinating movement, balance, and posture. When the cerebellum protrudes through the foramen magnum, it can compress the brainstem and spinal cord, leading to a variety of neurological problems.
Types of Arnold-Chiari Malformation
There are four types of ACM, classified according to the extent of the cerebellar herniation:
* Type I: The cerebellar tonsils (the lower parts of the cerebellum) protrude slightly through the foramen magnum, but the brainstem is not affected. This is the most common type of ACM.
* Type II: The cerebellar tonsils and the brainstem protrude through the foramen magnum. The brainstem may be kinked or compressed, which can lead to neurological problems.
* Type III: The cerebellum, brainstem, and spinal cord all protrude through the foramen magnum. This is the most severe type of ACM and is often associated with hydrocephalus (a buildup of fluid in the brain).
* Type IV: The cerebellum is so severely herniated that it is almost completely outside the skull. This is a rare and often fatal type of ACM.
Symptoms of Arnold-Chiari Malformation
The symptoms of ACM can vary depending on the type and severity of the malformation. Some common symptoms include:
* Headaches
* Neck pain
* Dizziness
* Nausea and vomiting
* Difficulty swallowing
* Vision problems
* Hearing loss
* Speech problems
* Weakness in the arms or legs
* Difficulty with coordination and balance
* Scoliosis (curvature of the spine)
Diagnosis of Arnold-Chiari Malformation
ACM is typically diagnosed with a combination of magnetic resonance imaging (MRI) scans and clinical evaluation. An MRI scan can show the extent of the cerebellar herniation and any associated abnormalities in the brainstem and spinal cord.
Treatment for Arnold-Chiari Malformation
The treatment for ACM depends on the type and severity of the malformation. In some cases, no treatment is necessary. In other cases, surgery may be necessary to relieve pressure on the brainstem and spinal cord.
Prognosis for Arnold-Chiari Malformation
The prognosis for ACM depends on the type and severity of the malformation. Most people with ACM are able to live full and active lives. However, some people with severe ACM may have lifelong neurological problems.