Diagnosis
Diagnosis is made through a combination of patient history, neurological examination, and medical imaging. Magnetic resonance imaging (MRI) is considered the preferred imaging modality for Chiari malformation. The MRI visualizes neural tissue such as the cerebellar tonsils and spinal cord as well as bone and other soft tissues. CT and CT myelography are other options and were used prior to the advent of MRI, unfortunately the resolution of CT based modalities do not characterize syringomyelia and other neural abnormalities as well.By convention, the cerebellar tonsil position is measured relative to the basion-opisthion line, using sagittal T1 MRI images or sagittal CT images. The selected cutoff distance for abnormal tonsil position is somewhat arbitrary, as not every person will be symptomatic at a certain amount of tonsil displacement, and the probability of symptoms and syrinx increases with greater displacement; however, greater than 5 mm is the most frequently cited cutoff number, though some consider 3–5 mm to be "borderline,"; pathological signs and syrinx may occur beyond that distance. One study showed little difference in cerebellar tonsil position between standard recumbent MRI and upright MRI for patients without a history of whiplash injury. Neuroradiological investigation is used to first rule out any intracranial condition that could be responsible for tonsillar herniation. Neuroradiological diagnostics evaluate the severity of crowding of the neural structures within the posterior cranial fossa and their pressure against the foramen magnum.
Hyperglycinemia may refer to one of two related inborn amino acid disorders that are characterized by elevated levels of glycine in the blood. Propionic acidemia, also known as "ketotic glycinemia"
Glycine encephalopathy, also known as "non-ketotic hyperglycinemia"