There has been growing concern in the Cavalier King Charles Spaniel community in recent years regarding a congenital malformation referred to as “”Caudal Occipital Malformation Syndrome.”” This is a condition in which the skull is too small to house the normal brain structures. The crowding results in fluid buildup within the brain (termed hydrocephalus) and the spinal cord (termed syringohydromyelia). The clinical problems that result from these changes can lead to scratching at the neck area, wobbly gaits, seizures, mentation changes, and discomfort in the spine and head. Though much attention has focused on medical and surgical treatment options for this disorder recently, there are still no objective measurements available to assess which young dogs are at risk of future disease progression or to evaluate the extent of correction with treatment. The aim of this study is to examine more objective variables including measurements of skull dimensions on MRI, measurement of cerebrospinal fluid (CSF) flow on MRI and ultrasound of arteries near the head (basilar artery) to try to find a reliable, minimally-invasive method of objectively classifying the severity of this disorder in a given patient, ascertain the likelihood of progression and measure the degree of correction after treatment.