A<unk> results when a watery, protective substance known as cerebrospinal fluid, that normally flows around the spinal cord and brain, transporting nutrients and waste products, collects in a small area of the spinal cord and forms a pseudocyst. A number of medical conditions can cause an obstruction in the normal flow of cerebrospinal fluid, redirecting it into the spinal cord itself. For reasons that are only now becoming clear, this results in<unk> formation. Cerebrospinal fluid fills the<unk>  Pressure differences along the spine cause the fluid to move within the cyst. Physicians believe that it is this continual movement of fluid that results in cyst growth and further damage to the spinal cord. In the case of<unk> omyelia, the<unk> can expand and elongate over time, destroying the spinal cord. Since the spinal cord connects the brain to nerves in the extremities, this damage may result in pain, weakness, and stiffness in the back, shoulders, arms, or legs. Other symptoms may include headaches and a loss of the ability to feel extremes of hot or cold, especially in the hands. Each patient experiences a different combination of symptoms. These symptoms typically vary depending on the extent and, often more critically, to the location of the<unk> within the spinal cord.<unk> s usually result from lesions that partially obstruct CSF flow. At least ½ of<unk> s occur in patients with congenital abnormalities of the craniocervical junction (e.g. herniation of cerebellar tissue into the spinal canal, called Chiari malformation), brain (e.g. encephalocele), or spinal cord (e.g. myelomeningocele—see Congenital Neurologic Anomalies: Brain Anomalies). For unknown reasons, these congenital abnormalities often expand during the teen or young adult years. A<unk> can also develop in patients who have a spinal cord tumor, scarring due to previous spinal trauma, or no known predisposing factors. About 30% of people with a spinal cord tumor eventually develop a<unk> <unk> omyelia is a paramedian, usually irregular, longitudinal cavity. It most often affects the cervical and thoracic regions but may extend further down or up into the brainstem <unk> obulbia).<unk> obulbia, which is rare, usually occurs as a slitlike gap within the lower brain stem and may disrupt or compress the lower cranial nerves or ascending sensory or descending motor pathways.
Syrinx 
Optician
Optic stalk
Optic recess
Ateronon
Microgyrus
Cauliflower ear
Otic vesicle