Abstract
Dear Sir We appreciate Dr Ravishankar's interest in and valuable comment on our paper (1). We agree that our patient shares some clinical features with ‘hair wash’ or ‘head bath’ triggering migraine (HWB) (2). As Dr Ravishankar mentioned, the headache is stereotyped, closely related to hot-bathing, throbbing in nature, intermittently (not always) associated with nausea and vomiting, and responsive to a kind of antimigraine prophylaxis, i.e. topiramate. However, the headache in our patient developed just after pouring hot water and reached maximum intensity within 2 to 3 min during the bath, which is different from HWB. HWB usually developed during drying the hair or the body after leaving the bathroom and could be prevented by using a hair dryer (2). Also, the headache was triggered exclusively by hot bath, although a certain group of HWB (11 of 1500 migraineurs and of 94 HWB) has hair wash or bath as the only trigger (1, 2).
As for now, the underlying pathological mechanism of the hot bath-related headache (HBRH) has not been established and HBRH is not included in the International Classification of Headache Disorders (ICHD-II) (3). Previous reports defined HBRH on the basis of a characteristic triggering factor, i.e. hot bath, and the specific temporal relationship between the trigger and headache (4–7). Therefore the stereotyped headache in our patient can be diagnosed as HBRH, although it does not perfectly match with type 1 or 2 of HBRH (1, 6). However, considering the throbbing nature of the headache and previous reports of the association between temperature stimuli and migraine, our patient might be classified as having migraine or probable migraine (3). Taking this point of view, some previously reported HBRH patients could also be diagnosed as having migraine (4–7). The presence of uncommon features of migraine, i.e. hot-bath as an exclusive trigger, association with cold-induced headache, and no personal and family history of migraine, led to a diagnosis of HBRH for our patient. However, the responsiveness to topiramate and characteristics of HBRH suggest that HBRH might share some pathophysiological mechanism with migraine (2, 4, 5).
Dr Ravishankar also raised the question about the diagnosis of cold-stimulus headache (CSH). CSH is a type of primary thunderclap headache featuring a severe intensity, sudden onset evolving in less than 1 min, and transient nature (3). As we described in the report, severe headache is more abruptly developed than HBRH, which usually evolved over 2 to 3 min, and more severe in intensity, but lasted for an unusually long period (1). The longer duration is somewhat confusing, but confers the uniqueness of both hot bath- and cold-induced headache in our patient.