There are four types of Chiari malformations and these are put down below in greater detail.
This is the most commonly observed type of Chiari malformation; it is often seen in children. In this condition, the lower region of the cerebellum (excluding the brain stem) protrudes into an opening near the base of the skull. This opening is called the foramen magnum. When in normal medical condition, only the spinal cord must supposedly pass through the opening.
In type I Chiari malformation, the parts of the brain get pushed downwards, as they are considered too big for the skull. When these parts are pushed from the skull towards the spinal cord, it creates a pressure at the base of the brain, and also hinders the flow of cerebrospinal fluid (CSF), both to and from the brain region.
Chiari malformation can also run through families, and chances are that some children having this disorder may be inheriting a faulty gene, resulting in problems related to skull development in the womb stage. At the same time, the risk of a Chiari malformation being passed on to a child is negligible and even if the kids inherit it, they will most likely not develop the symptoms. Individuals with type I Chiari malformation exhibit the signs during the latter part of their lives. Those include headaches, insomnia, dizziness and body equilibrium issues, besides blurred vision, neck pain, swallowing problems, hearing loss, etc.
Type I Chiari malformations were earlier observed in just one in every 1,000 individuals. However, modern diagnostic methods have proved that the condition is much more common. Type I Chiari malformations can be detected by an MRI scan. A brain scan can bring up abnormalities, if any in the structure of an individual's brain and spine. Chiari malformation can be managed with medications, such as painkillers, for relieving any headache and neck pain. A decompression surgery can help reduce the pressure at the base of the brain. This also involves widening the space in the foramen magnum - the region towards the opening of the skull.
Most people suffering from Chiari malformation also exhibit another medical condition called syringomyelia, which involves formation of a tube-shaped cavity within the patient's spinal cord. This cavity filled with fluid is called syrinx, and which can elongate by damaging the critical spinal cord region. This, in turn, causes pain, weakness, numbness, stiffness and other conditions such as bowel/bladder function, paralysis, etc.
This type of malformation is commonly seen in children born with spina bifida. Spina bifida represents the incomplete development of the spinal cord region and also its protective covering. It is also generally referred to as classic Chiari malformation. With this type, the cerebellum as well as the brain stem extends into the foramen magnum.
This is a rare type and is considered a serious form of Chiari malformation. It is characterised by a protrusion or herniation of the brain stem and the cerebellum through the foramen magnum, and further into the spinal cord. This malformation can lead to severe neurological defects.
Type IV is another rare kind that is indicated by underdeveloped or incomplete cerebellum, and is associated with the exposed regions of the skull and the spinal cord.