Lateralized central facilitation of trigeminal nociception in cluster headache

Background: Central facilitation of trigeminal pain processing was demonstrated in different primary headache and facial pain disorders. Whether it is also part of the pathophysiology of cluster headache (CH) has been intensively discussed due to inconsistent study results.

Methods: Sixty-six patients with CH (18 episodic CH inside bout, 28 episodic CH outside bout, 20 chronic CH) according to the ICHD-II-classification, as well as 30 healthy controls were investigated using simultaneous recordings of the nociceptive blink reflex (nBR) and pain related evoked potentials (PREP) following nociceptive electrical stimulation on both sides of the forehead (V1).

Results: NBR latency ratio (headache side/non-headache side) was decreased in all CH patients independently of CH subtype compared with healthy controls indicating central facilitation at brainstem level. Area-under-the-curve (AUC) ratio was increased in patients with episodic CH inside bout only. PREP showed decreased N2 latency ratio in patients with chronic CH indicating central facilitation at supraspinal (thalamic or cortical) level.

Conclusions: In CH asymmetric facilitation of trigeminal nociceptive processing predominantly on brainstem level was detected. This alteration is most pronounced in the acute pain phase of the disease, but appears to persist in remission periods. Only chronic CH patients show additional changes of the PREP prompting to supraspinal changes of pain processing related to the chronic state of disease in regard to neuronal plasticity, which exceeds changes observed in episodic CH.