Chronic tension-type headache: where are we?

Primary headache syndromes may generally be distinguished as being either episodic, such as typical migraine or cluster headache, or chronic, such as chronic tension-type headache (CTTH) or hemicrania continua. In truth it is chronic headache, and most particularly chronic daily headache (CDH) in its various forms, that gives the sub-speciality of headache a bad name. Daily headache in all its manifestations probably effects 5% of the population (Scher et al., 1998; Castillo et al., 1999), of which about half is clear-cut, at least on clinical grounds, CTTH. If neurology is to take headache into the next century, as either necessity or interest dictate, then the common headache syndromes must be adequately understood and it is timely to think about daily headache. It is on this background that we can greet the positive observations that Olesen's group report in this issue of Brain (Ashina et al., 1999a), and the similarly challenging therapeutic data recently reported in The Lancet (Ashina et al., 1999b). Two fundamental issues need to be answered in regard to CTTH: the first is its nature or basis, and the second, related issue is how TTH should be handled in terms of nosology. This new work contributes in some measure to both questions. Crucial to any attempt to improve the management of CTTH in clinical practice is to develop an understanding of what the syndrome actually represents. The International Headache Society (IHS) Diagnostic Classification (Headache Classification Committee of the International Headache Society, 1988) sets out clear operational criteria, but they are essentially nihilistic. The IHS classification says more of what CTTH is not than of what it is: preferably bilateral, non-pulsatile headache without vomiting but perhaps nausea, and with no sensory sensitivity to head movement nor light and sound, although one of the latter pair is acceptable. In this definition system CTTH is little more than lots of episodic TTH, which in turn is lots of not-migraine. Although this is not absolutely true, it does highlight the problems of definition with TTH. TTH can come with and without muscle tenderness, but does that tell us about the nature of that tenderness or its role in the pathophysiology? Ashina and colleagues have shown us that summary scores for muscle hardness, measured with a remarkably ingenious device of Professor Sakai's, are reduced by the nitric oxide synthesis (NOS) inhibitor N G-monomethyl-L-arginine hydro-chloride (L-NMMA), and muscle tenderness is also reduced (Ashina et …