Morphometric Analysis of Left & Right Tonsils in Adult Symptomatic Type 1 Chiari Patients and Healthy Controls

Historically, CMI has been radiographically defined by cerebellar tonsillar descent below the foramen magnum (FM) more than 5 mm (2). This measurement is typically made with a single sagittal plane T1-or T2-weighted MR image. Studies have obtained additional morphometric measurements to help diagnose CMI, and establish normal values (3,4). These studies were somewhat These studies were somewhat successful in differentiating CMI patients from healthy subjects. However, results from these studies have shown that the standard TD measurement does not necessarily correlate with neurological symptom severity as patients with CMI-like symptoms have been found with a TD of less than 5 mm position below the FM (6,7). Also, a variety of morphometric measurements have been found insufficient to differentiate disease states related to CMI such as syringobulbia (8). Past studies have reported that the TD measurement is not a good measure for diagnosis of CMI, yet it is still being used today (7). The primary goal for this study is to provide a better method for diagnosing CMI. One aspect that has not been analyzed in previous work is morphometric measurement of the left and right tonsil with using a constant reference point in the mid-sagittal plane. We hypothesize, using the proposed methodology, that the cerebellar tonsil descent relative to the FM will be lower based solely on a mid-sagittal slice compared to the 7 clinical operators measurements