Lignocaine and headache: an electrophysiological study in the cat with supporting clinical observations in man.

Chronic daily headache (CDH) is a particularly difficult type of headache to manage, with an uncertain pathophysiology. Intravenous administration of lignocaine has been suggested as a possibly useful option in the control of this syndrome. We have surveyed prospectively patients with CDH (selected for this study as those with 6 or more months of continuous pain with at least weekly exacerbations that, taken in isolation, would fulfil International Headache Society diagnostic criteria for migraine without aura). Intravenous lignocaine (2 mg/min) by infusion over a 2-day period rendered 26% of patients pain free, with a further 42% having at least a 50% improvement in the pain. Continued benefit was associated with commencement of prophylaxis with a tricyclic antidepressant or monoamine oxidase inhibitor after completion of the lignocaine infusion. In an animal model of craniovascular nociception, using electrical stimulation of the superior sagittal sinus and recording of single unit activity and sensory evoked potentials in the spinal trigeminal nucleus in the upper cervical spinal cord of the anaesthetised cat, the effect of lignocaine was examined. Lignocaine reduced both the probability of cell firing and the size of the trigeminal evoked potential in the animals studied. The reduction was both substantial (more than 25% in each case) and dose-dependent. Taken together the data suggest that CDH is likely to be a disorder of central craniovascular nociceptive control and that lignocaine acts to interrupt a part of the pathway involved but is unlikely to act at the central generator of the disorder.