Experimental cranial pain elicited by capsaicin: a PET study

Area of Science:

• Neuroscience
• Pain Research
• Medical Imaging

Background:

• Previous PET studies suggested brain stem activation in migraine without aura, termed the 'migraine generator'.
• The exact neural mechanisms underlying migraine attacks require further investigation.
• Understanding trigeminal nerve pain pathways is crucial for headache research.

Purpose of the Study:

• To test the 'migraine generator' hypothesis by examining brain activity during experimentally induced trigeminal pain.
• To investigate the role of the brain stem in acute pain versus chronic headache conditions.
• To identify brain regions involved in trigeminal pain processing.

Main Methods:

• Positron emission tomography (PET) was used to measure regional cerebral blood flow (rCBF).
• Seven healthy volunteers received subcutaneous capsaicin administration on the forehead to induce trigeminal pain.
• Brain activity was compared between acute pain and pain-free states using standardized stereotactic space.

Main Results:

• Experimentally induced trigeminal pain activated bilateral insula, anterior cingulate cortex, cavernous sinus, and cerebellum.
• No significant brain stem activation was observed in healthy volunteers during acute pain.
• Increased activation in the cavernous sinus region suggests its involvement in trigeminal pain transmission.

Conclusions:

• The study did not support the 'migraine generator' hypothesis originating from the brain stem for migraine without aura.
• The findings indicate that the cavernous sinus may play a significant role in processing pain transmitted via the trigeminal nerve.
• This research differentiates general trigeminal pain mechanisms from specific headache disorders.