Objective, Background, and Methods.—Ever since it was proposed by Ekbom and Kugelberg back in 1968 on the basis of the different location of head pain during attacks, the differentiation of cluster headache into an upper syndrome (US) and a lower syndrome (LS) has been regarded as a purely academic distinction. To evaluate whether this differentiation is indeed well founded and to understand its possible significance in the light of current pathogenetic knowledge, we rigorously applied Ekbom and Kugelberg's classification criteria to a sample of 608 patients with cluster headache (CH; 440 men and 168 women), including 483 with episodic CH, 69 with chronic CH, and 56 with CH periodicity undetermined.
Results.—Of these patients, 278 could be classified as US sufferers and 330 as LS sufferers. Our data analysis showed statistically significant clinical differences between the two syndromes: pain location was more common in the ocular, temporal, and nuchal regions among LS sufferers; in addition, patients with LS reported not only a higher rate of autonomic symptoms, but also a higher predominance of nasal congestion, ptosis, and forehead and facial sweating among these symptoms.
Conclusions.—Based on current anatomofunctional knowledge and on the most recent pathogenetic findings, we believe that changes in hypothalamic activity posteroinferiorly may lead to activation of the caudal part of the spinal trigeminal nucleus by way of the hypothalamus, midbrain, and trigeminal nerve fibers and consequently to activation of the trigeminovascular system with a different location in the two syndromes. More specifically, there seems to be a larger and more extensive involvement of the subnucleus caudalis in LS compared with US, where only its ventrocaudal portions are likely to be affected.