If there is pressure on the lower brainstem, its first symptom may be death. Otherwise symptoms vary depending on whether the spinal cord, brain stem, nerves or their blood supply is affected by the pressure.
Symptoms become apparent when the neck is bent. They include:
- Periods of confusion or conscious awareness that doesn't seem normal
- Difficulty swallowing or saying words due to loss of muscle control after damage to the nervous system (dysarthria)
- Loss of sensation
- Pain in the back of the head
- Loss of the ability to know how joints are positioned
- Tingling or numbness in the fourth and fifth fingers
- Tingling or numbness in the middle part of the forearm
- Tingling when the neck bends forward or backward
- Weakness or stiff,awkward movements of the of the arms and legs
Patients will go into a pool and notice that below the belly button the water is not as cold as it is above.
Causes and Risk Factors
Basilar invagination can be present at birth. If the condition develops after birth, it is usually the result of injury or diseases. If due to injury, about half the time it is caused by vehicle or bicycle accidents; 25% of the time by falls and 10% of the time by recreational activities such as diving accidents.