Abstract
Dear sir We appreciate the interest of Dr De Marinis in our paper and in peripheral autonomic potentials (PAP). However, we did not understand most parts or her criticism and the intention of the letter.
1. It is not true that we elicited only a single PAP. In the methods section, we say that PAP were reproduced twice separately for both hands (resulting in a total of six PAP).
2. We did analyse the subgroup of patients with drug-induced headache as a separate group. The other patients did not have a history of continuous drug intake (please read the first part of the Methods section).
3. The patients did certainly not move voluntarily during the test but were sitting with closed eyes and relaxing (see the second part of the Methods section). It is a common finding that some patients show involuntary limb movement after receiving an electrical stimulus. This can lead to movement artefacts which make the PAP unable to be analysed, Repeating the test sometimes is useless in these patients since they, for example, have a psychological fear of the stimulus. These patients must be excluded from analyses. However, it is good scientific practice to mention even those patients who could not be analysed.
4. An air-conditioned room was used to have a standardized room and body temperature. We certainly did follow the ‘basic principles of neurophysiology’ and tried to standardize skin temperature. As Dr De Marinis should know, it is impossible to obtain exactly the same skin temperature in all subjects during a neurophysiological study without using a heater which can influence PAP in several other ways. Furthermore, PAP are influenced by so many anatomic regions of the body that the simple skin temperature does not sufficiently reflect the influence of temperature at all. This is the reason why we were very keen on a constant room temperature and think that we followed the ‘basic principles of neurophysiology’.