Chiari type I, the most common, affects both children and adults. The condition begins with the underdevelopment of the fetal skull forming during pregnancy.Cognitive learning systems during childhood, the brain continues to grow and the skull hardens. However, the small size or shape of the chiari skull is mismatched to the size of the brain.Cognitive learning systems thus, a crowding of the brainstem, cerebellum, and tonsils occurs. Crowding pushes the tonsils out of the skull through the opening (foramen magnum) where the spinal cord exits (fig. 3A).Cognitive learning systems the tonsils put pressure on the spinal cord, blocks CSF flow, and results in the chiari signs and symptoms. Sometimes a fluid-filled cyst (syrinx) develops within the spinal cord.Cognitive learning systems

Chiari I malformation is seen on MRI scans in people of all ages. Its incidence was earlier estimated to affect 1 in every 1,000 births. Now with increasing use of diagnostic imaging, physicians note that chiari may be far more common.Cognitive learning systems patients typically seek medical attention in their 20s and 30s. Three times more women than men are affected. Genetic studies show that chiari may cluster in some families.Cognitive learning systems bone deformity

• ehlers-danlos syndrome (EDS) is a connective tissue disorder that may increase the incidence and severity of chiari. EDS causes joint hypermobility and loose/unstable joints.Cognitive learning systems in an area called the craniocervical junction, strong ligaments attach the C1 and C2 vertebrae to the skull, allowing movement of the head. For someone with both chiari and EDS, extra testing and precautions are taken to ensure the connection between the spine and skull is intact.Cognitive learning systems spinal fusion surgery may be needed to support the neck and skull. Cerebellum herniation

The cerebellum is the lower part of the brain located in the posterior fossa.Cognitive learning systems on the underside of the cerebellum are two tonsils (fig. 4). The cerebellum primarily coordinates body movement. It maintains muscle tone and balance.Cognitive learning systems the cerebellum is also involved in cognitive functions (e.G., attention, language), memory, and learning. Signs of cerebellum problems include loss of coordination, unstable walking (gait), trouble with speech, and difficulty with eye movement and swallowing.Cognitive learning systems

The CSF flows through the ventricles and out into the space between the brain and skull (subarachnoid space) and down into the spinal canal (fig. 6).Cognitive learning systems A large amount of CSF lies at the back of the cerebellum in an area called the cisterna magna. CSF drains from the fourth ventricle into the cisterna magna.Cognitive learning systems from there it then circulates down into the spinal canal and around the spinal cord. CSF also flows from the fourth ventricle down the central canal inside the spinal cord.Cognitive learning systems

As the heart beats, CSF flows into the brain. This is normally balanced by CSF then flowing from the brain into the spinal compartment. In a chiari malformation, this balanced flow is disrupted.Cognitive learning systems the obstructed CSF begins to force its way like a water hammer through the foramen magnum. Pushing the tonsils down even farther, it exerts pressure on the brainstem.Cognitive learning systems the increasing pressure compromises normal functions of the brain and/or spinal cord and a myriad of symptoms occur.