NEURALGIA DE ARNOLD
The transcranial Doppler (TCD) is an important noninvasive resource to evaluate cerebral blood flow by using ultrasound waves. It was first described by Aaslid, in 1982, and since then its applications have become considerably wider. The first studies using TCD in patients presenting primary headaches also took place during the eighties. In this article, the authors review historical and technical aspects of TCD. In addition, they analyze the results of recent papers on TCD and headaches in general, emphasizing migraine and cluster headache. In conclusion, the authors agree that TCD has helped to clarify physiopathological aspects of some primary headaches; however, it poorly contributed to their diagnosis. They also conclude that there is a lack of methodological consensus in this area, resulting in many inconclusive results.