Abstract
Introduction
Chiari malformation type 1 (CM-1) is diagnosed by more than 3 or 5 mm caudal displacement of the cerebellar tonsils through the foramen magnum. This definition is a simple and easy method neuroradiologically, but it is obscure which is 3 or 5 mm. The purpose of this study is to analyze their clinical symptoms and radiological features.
Materials and Methods
We had 7788 new outpatients in our neurosurgical hospital in 2013 and 2014. In whom, patients undergone head CT or MRI were examined retrospectively. We diagnosed chiari marformation type 1 using more than 3 mm tonsillar herniation. Their clinical symptoms and the following measurements were analyzed: the distances from the pontomedullary junction (PMJ) to the basion (PMJ-Ba), PMJ to the basion-opisthion (PMJ-BO), the distances from the basion-opisthion to tip of the cerebellar tonsil, from BO to the obex (BO-obex), and from basion to opisthion, the clivo-axial angle, and the length of the clivus using T1-weighted sagittal images.
Results
There were 32 patients with CM-1 aged from 10 to 78 years (mean: 37.6 years) consisted of 8 men and 24 women. In whom 20 patients with tonsillar herniation of less than 5 mm were determined as T-3 group (T-3) and remained 12 patients as T-5 group (T-5). No patients had syringomyelia. Headache was the most common symptom. Four patients in T-3 group were diagnosed incidentally, 3 in head injury and one in memory disturbance. The distances of PMJ-Ba, PMJ-BO, BO-obex, BO, the clivo-axial angle, and the length of the clivus were similar between both groups.
Conclusions
The patients in both groups had similar sympotms and posterior cranial fossa structures, however, patients in T-3 group without symptoms associated with CM-1 were diagnosed incidentally. Chiari malformation type 1 should be diagnosed based on not only tonsillar herniation but also clinical symptoms and other MRI findings such as brainstem ptosis.