Foramen magnum

Looks like

The large oval hole in the occipital bone at the base of the skull, with the skull's two joint knobs for the spine beside it.

What it does

Lets the brainstem pass down into the spinal cord, with the vertebral arteries and the accessory nerves beside it.

Keeping it well

Part of the brain can be pushed into it (a Chiari malformation, or brain swelling after an injury). Headache on coughing, numb hands or unsteady walking need a doctor; drowsiness after a head injury is an emergency.

Related conditions

• Achondroplasia
• Acromegaly
• Brain abscess
• Fractures
• Fragility fracture
• Frailty & falls in older age
• Hyperparathyroidism
• Osteogenesis imperfecta (brittle bone disease)
• Osteomalacia & rickets
• Osteomyelitis (bone infection)
• Osteoporosis
• Paget's disease of bone
• Sarcoma
• Traumatic brain injury (moderate to severe)
• Vitamin B1, C and other deficiencies
• Vitamin D deficiency