Morphometry of Foramen Magnum: An Anatomical Study

Introduction: The knowledge of foramen magnum dimensions is important for clinicians to highlight the malformations like Arnold Chiari malformation and Achondroplasia. Its morphometry is helpful for neurosurgeons and for forensic experts as well. Foramen magnum (FM) is a large oval opening in the occipital bone of skull that transmits part of brain stem, spinal cord and many related structures Aims & Objectives: To determine the variations in transverse and antero posterior diameters of foramen magnum and foramen magnum index in dry skulls of adults in Pakistani population. Place and duration of study: The study was conducted at FMH College of Medicine & Dentistry, Lahore in December 2021 on 99 dry human skulls. Material & Methods: The foramen magnum of 99 dry skulls of human adults of unspecified gender and of unknown exact age, from the collection of Anatomy Department in FMH college of Medicine and Dentistry, Lahore, Pakistan, was examined to evaluate the dimensions of FM. Digital caliper was used to measure the antero-posterior diameter (APD) and transverse diameter (TD) of foramen magnum (FM) in dry skulls of human adults and then foramen magnum index FMI was calculated by dividing APD by TD. Results: The mean values of transverse and antero posterior diameters of foramen magnum in dry human skulls were found as23.18+7.68 and 29.22+7.52 respectively. The mean value of foramen magnum index was 1.30+0.22. Conclusion: Our study determined variations in diameters of FM and FMI in the skulls of Pakistani population. Antero posterior diameter of foramen magnum is more than its transverse diameter and majority of skulls show oval shaped FM. The results of this study may help the neurosurgeons, anthropologists, morphologists, clinical anatomists and forensic experts.