Introduction: The study aims at providing an overview of morphometric measurements of the skull
baselines in normal Indian population and compares these dimensions with those of
other races and ethnicities. This study will help in defining “normal” baseline values
for Indian population. It will also compare dimensions as measured on X-ray and computed
tomography (CT) scan to assess the reliability of X-ray as a diagnostic modality for
the assessment of the skull baselines in Indian population. Materials and Methods: Retrospective study with a sample size of 116 patients and duration of 30 months.
Results: The mean value for distance between dens tip and Chamberlain line on CT was 0.498
mm and on X-ray was 0.528 mm and for the distance between dens tip and McGregor line
on CT was 0.213 mm and on X-ray was 0.228 mm. The mean distance between the dens tip
and McRae line was 4.67 1.69 mm on CT scan and 4.7 1.76 mm on X-ray. Conclusion: There was not a single patient in whom the dens tip crossed the McRae line. Any protrusion
of the dens tip beyond the foramen magnum is abnormal. Hence, the McRae line is easiest
to understand and remember. Furthermore, the Chamberlain and McGregor lines rely on
identifying the hard palate, which may not be included in routine X-ray, CT, and magnetic
resonance imaging studies depend on the field of view. Hence, we recommend the use
of McRae line for screening purposes while evaluating pathologies of the craniovertebral
junction. X-ray is a reliable diagnostic technique for assessing morphometry of the
skull baselines in an emergency or rural setting if facility for CT scan is not available.
Key-words:
Basilar invagination - Chamberlain - McGregor - McRae
