Clinical significance of morphological and morphometrical analysis of foramen magnum

Abstract

Introduction: The foramen magnum is a transitional zone between cranial cavity and spinal canal, and it is related with the very important neuro-vascular structures like vertebral arteries, spinal accessory nerves and spinal arteries and terminal part of medulla oblongata. Therefore, thorough knowledge of morphometric and morphological variation of foramen magnum is important for authentic radiological diagnosis and surgeries in the area of cranio-cervical junction. Materials and Methods: This study was done on 70 dried human skulls taken from the Department of Anatomy, TS Misra Medical College & Hospital, Era’s Lucknow Medical College & Hospital, and KGMU, Lucknow. The shape of foramen magnum was observed and transverse and antero-posterior (AP) diameters of foramen magnum (FM) were measured with the help of vernier caliper. Foramen magnum index (FMI) and foramen magnum area (FMA) were also calculated. Results: The study showed six types of shapes of foramen magnum. The oval shaped foramen magnum was found in 47% (in 33 skulls), round 30% (in 30 skulls), tetragonal 10 % (in 10 skulls), triangular & irregular 10% (in 5-5 skulls), pentagonal 2% (in 2 skulls), and hexagonal 1% (in single skull). The mean anteroposterior and transverse diameter were 34.3±2.90mm and 28.9±2.80 mm respectively. The mean foramen magnum index and Foramen magnum area were 77.80±27.80 and 845.90±87.50 mm2 respectively. Conclusions: The data obtained from the present study will be useful to the neurosurgeons prior to the surgeries in the area of cranio-cervical junction and posterior cranial fossa. The morphometric and morphological knowledge of the foramen Magnum has important clinical implications in the prognosis and treatment of various neurological pathologies like Arnold Chiari syndrome, Achondroplasia and posterior cranial fossa lesions. Keywords: Foramen magnum, Transcondylar approach, Foramen magnum index, Foramen magnum area, Transverse diameter (TD), Anteroposterior diameter, Trigonal.