The trigeminal nerve is often implicated in head and facial pain conditions.
Other than the special senses (sight, smell, taste, hearing) all of the other sensory information (pressure, pain, mucsle position, feeling of muscle contraction, temperature, blood vessel diameter) from the head and face is carried, primarily via the Trigeminal nerve, with some minor contribution from the facial (scalp muscles), glossopharyngeal (middle ear) and vagus (outer ear) nerves.
The information from all these nerves is carried back to the nucleus which sits in the brainstem in the upper cervical spine. Here it is relayed onto central nerves to be carried up into the brain, and you become “aware” of the sensations.
What we know about chronic headache and migraine from reflex studies and PET scans, is that this “relay area” in the brainstem is overactive. It sends signals to the brain to cause you to feel sensations in the head and face that aren't really there. It is the overactivity in this area that the triptans help to control (i.e. your sumatriptan) by helping the body to absorb serotonin, which “turns down” the activity levels and stops the false signals being sent.
For example, throbbing is a common pain in migraine - yet it has been shown over and over again that there is no change in blood flow in the head or on the brain. What is happening is that the nerves that relay this “throbbing” information to the brian have been switched on in the brainstem, so throbbing is what you feel. Some can even feel a pulse with their hand.
In your case, the migraine “pain behind the eye” is your brain interpretting that the muscles are on, either contracting (pressure) or spasming (sharp pain), because the nerves in the brainstem have been switched on. The actual muscles behind the eye, much like the blood vessels in the example above, are not doing anything. Your brain just thinks they are.
The typical types of pain behind the eye are “pressure” or “sharp” pains. When a muscle contracts it feels like “pressure”, or if it spasms it feels “sharp”.
So what is causing the brainstem to be overactive?
The part of the brainstem that is affected receives direct input from the upper 3 cervical nerves. We are part of a growing chorus saying that a significant proportion of this overactivity relates to manageable and treable problmes in the upper cervical spine. It does not account for all cases of chronic headache and migraine, but it is a significant factor in a vast majority of cases and it is often overlooked.
At the Melbourne Headache Centre we beleive, that once you have ruled out other significant pathology (and that includes your blood pressure - which should be excluded by your doctor as a cause) as a possible cause of your condition, the upper cervical spine should be excluded as a pain generator in ALL headache and migraine conditions.
Director and Senior Clinician - Melbourne Headache Centre
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