The weakness in the body's connective tissues that is caused by Ehlers-Danlos Syndrome(EDS) may cause a lack of stability of the neck and skull. This lack of stability is called Cranio-Spinal Instability(CSI). In CSI, the bones in the neck are able to move out of their proper positions, tissues can sag down out of place, and spinal fluid flow may be impaired. The bone and tissue movement is often noticeable only when an individual with CSI is in an upright position and the bones and tissue return to their normal positions when the individual returns to a horizontal position. In severe cases, CSI may be accompanied by cranial settling
In an individual with Ehlers-Danlos Syndrome (EDS) and Craniospinal Instability (CSI), Cranial Settling is likely to occur. In Cranial Settling the tissues in the neck are weak, due to EDS, and the cervical bones are not held in place thus causing instability. This forces the cerebellar tonsils out of the skull into the spinal column through the small hole at the base of the skull called the foramen magnum, a phenomena called cerebellar herniation. When the cerebellar tonsils are out of place, they take up space normally allotted for the cerebral spinal fluid (CSF), the brainstem, and all the arteries and veins leading through here to the brain. This puts pressure on the cerebellar tonsils and the brainstem which damages both structures progressively over time. The cerebellar tonsils are the lowest part of the cerebellum, which controls the sensory perception and motor control systems of the body. The brainstem controls the autonomic nervous system, or everything your body does without you having to thinking about it - heart rate, respiration, blood pressure control, etc. Damage to these systems is very serious, and can even be life-threatening. CSI may also allow the odontoid bone at the front of the neck to push backwards into the brainstem, causing even more damage to this structure. In addition to this, due to the crowding of the cerebellar tonsils, brainstem, and cranial arteries and veins, CSF flow may be impaired which deprives the brain and spinal cord of nutrients that they need. Spinal fluid continuously flows around the brain and spinal cord, bringing them essential nutrients. In an individual with cranial settling, however, there may not be enough room left at the opening of the skull for the spinal fluid to effectively flow.