Hot water epilepsy: A rare form of reflex epilepsy

Introduction

Hot water epilepsy (HWE) is a well-defined entity within the forms of reflex epilepsies, which occurs while bathing with hot water.[12] Allen first described HWE in 1945 and subsequently there have been many reports of its prevalence in both children and adults.[2] HWE is a term used to encompass a reflex epileptic condition, characterized by pouring hot water (40–50°C) on the head.[3] although it has been reported from all parts of the world, it is more prevalent in South Indian population as most of the reported cases have been from there.[4] It has been rarely reported in other European countries and isolated case reports have been published from Japan and Turkey.[5] The differences among countries may depend on climatic conditions, bathing habits and probably genetic susceptibilities. Here, we report two cases of HWE from Saudi Arabia.

Case Reports

Discussion

Reflex epilepsy is a condition in which seizures are provoked exclusively by an external stimulus and account for 6% of all epilepsies.[6] HWE is an unusual form of reflex epilepsy, precipitated always, by bathing in hot water. Thus, this mode of reflex epilepsy requires a specific thermal cutaneous stimulus. Both partial and generalized tonic seizures have been described secondary to hot water bathing, suggesting that the seizures might be influenced by the same afferent pathway.[78] Most of the reported cases in the past were from southern parts of India and none of our patients had their origin from there, as they were born to Saudi parents, although the first Saudi patient's mother had an Indian origin.

Hot water is known to precipitate severe myoclonic epilepsy in infants, but HWE is an unique form of generalized or partial tonic, clonic seizures, even reported exceptionally with cold water, during tub bathing or taking a shower.[9] The exact mechanism of HWE remains uncertain and seizures had been reported during a bath even when water is not poured over the head. Self-induced seizures occur in 10–20% of the patients.[10] In India, ritual immersion baths at temperature around 45°C are reported to trigger epileptic fits.[4] At this higher temperature of water, warmth receptors were said to be stimulated at the highest rates. Thus, an aberrant thermo-regulatory center, which is sensitive to sudden spurt in regional temperature following hot water bath, could be the precipitation cause for HWE.[10] Another reasonable mechanism, described on physiological grounds, could be a defective inhibitory influence over afferent volleys of somatosensory stimuli such as warm or hot water poured over large body surface. In this context, HWE could be comparable to febrile seizures in the above-suggested mechanism of occurrence, although fever-induced fits were not significant in these patients.[11] An experimental animal model mimicking HWE has been developed in order to understand the pathophysiological mechanism.[12] Familial clustering in HWE has suggested a genetic component as the probable cause of the disorder and a genetic locus in the 10th chromosome had been identified (10q21,3-q22,3).[13] The diagnosis is entirely based upon history only, as inter-ictal electroencephalography and neuroimaging studies were reported to be normal. Shankar et al. had reported autopsy findings in three patients with HWE and concluded that there could be an aberrant thermoregulation in such genetically susceptible patients with possible environmental influences.[14] Kowcas et al. reframed the term as bathing epilepsy rather than hot water epilepsy because their patients had seizures with warm water but not with hot water.[15] Nechay et al. postulated altered autonomic regulations or some form of channelopathies as the underlying mechanisms for this disorder.[16] Satishchandra related this disorder as a form of geographically specific epilepsy syndrome, where some cases might have genetic basis with added environmental influence.[17]

There is no role of anti- epileptic treatment in HWE because of its symptomatic nature of seizures; altering the temperature of water or changing the method of washing would prevent the occurrence of these seizures[18] . Anti-epileptic drugs are only indicated when such patients continue to have seizures even during regular baths with normal water temperature or non-reflex seizures.[15] Since seizures show a tendency to decrease spontaneously, withdrawal of medication, if it had been given, should be carefully undertaken only after several months. The above two case descriptions were made to highlight the rarity of its occurrence and to emphasize that HWE could be controlled exclusively by lifestyle modification without resorting to anti-epileptic medication.