Orthopaedics

Foramen magnum – Significance of Foramen magnum

The word “foramen” is a Latin word which means a great hole. Based on the anatomical features, of the foramen magnum, its name is coined. It is found as a hole through a bone. The foramen magnum is a large passage found in the occipital bone of the cranium. In the base of the human skull, several circular apertures are found. Foramen magnum is the largest among those openings.

Significance of Foramen magnum –

  • In simple terms, people say that the hole through which the spinal cord passage is called the foramen magnum.
  • This opening indicates the exact angle of the spinal column which will decide whether our body is horizontal (resembling that of a horse) or vertical (like in case of humans).
  • The position of this passage has been used by several anthropologists to determine the ability to walk upright in human ancestors.
  • This hole is placed much towards the back of the head in humans today compared to those in great apes. This adaptation uses lesser musculature (neck muscles) to support the skull.
  • An extension of the spinal cord, called the medulla oblongata enters and exits the skull vault through the foramen magnum. The spinal cord exits the opening to connect with the brain. It then merges with the lowermost portion of our brain (the medulla oblongata).
  • Besides the spinal cord, several nerves, tendons and blood vessels also pass through this opening.
  • Functions of the foramen magnum are mentioned below –
    • transmission of medulla oblongata along with its membranes
    • transmission of spinal accessory nerve
    • transmission of vertebral arteries
    • transmission of anterior spinal arteries and posterior spinal arteries
    • transmission of membrana tectoria
    • transmission of alar ligaments

Foramen Magnum Stenosis –

  • Achondroplasiac children have higher mortality rate. The reason behind the large number of deaths is compression of the spinal cord. It can cause sudden deaths in children.
  • Foramen magnum stenosis is a congenital issue. In this case, the foramen magnum is not large enough to allow the spinal cord to pass through it easily. Improper formation of bones and cartilages in humans is termed as Achondroplasia, which is the common cause of Foramen magnum stenosis. Achondroplasia is commonly referred to as some kind of dwarfism.
  • Achondroplasia makes the size of the opening much smaller. Such cases, though are not always harmful, but can be fatal in many other cases.
  • This requires surgery to avoid any deaths or undesirable disability.

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