Epilepsy, Hot Water, 1

A susceptibility locus for hot water epilepsy (HWE1) has been mapped to chromosome 10q21.3-q22.3.

Another locus for hot water epilepsy, HWE2 (613340), maps to chromosome 4q24-q28.

Description

Hot water epilepsy (HWE) is a form of reflex or sensory epilepsy in which seizures are precipitated by immersion in hot water or pouring of hot water over the head during bathing. The seizures are usually complex partial, but about 33% of patients experience secondary generalization. There are no additional neurologic abnormalities (Satishchandra, 2003).

Clinical Features

Allen (1945) provided an early description of hot water epilepsy in 1 of a series of 21 patients with various forms of reflex epilepsy, defined as a condition in which a sensory stimulus precipitates a seizure. The patient was a 10-year-old boy with a 6-month history of 'fits' only when he was put in his bath. He went stiff, his eyes stared, and he lost consciousness.

Mani et al. (1968) reported a series of 42 Indian patients with hot water epilepsy. These patients accounted for 2.3% of over 1,810 patients with epilepsy seen over a period of 7.5 years. There were 24 males and 18 females, and most were between 6 and 15 years of age. Five (12%) had a family history of the disorder. Thirty patients had symptoms only with hot water: 16 when poured on the head and 14 when poured on the trunk and shoulders. Nine patients had symptoms in both a hot and cold bath. Nine (21.4%) patients also had non-reflex types of seizures, and 4 (29%) of 14 patients available for follow-up developed non-reflex seizures. Within seconds of application of the hot water, the child would appear dazed, make smacking movements of the lips, and appear confused for about 2 minutes. This was usually followed by sleep, although secondary generalized tonic-clonic seizures occurred in 14 (33.3%) patients. Neurologic examinations were normal, and none had mental retardation. The few interictal EEGs available showed no abnormalities. Mani et al. (1968) postulated a focal discharge arising from the temporal lobe.

Mani et al. (1974) reported a series of 108 Indian patients with hot water epilepsy seen over a period of 2.5 years. These patients accounted for 9% of all epilepsies. Sixty-five of the patients had seizures provoked only by hot water (group 1), whereas 43 had seizures without baths as well (group 2). A history of parental consanguinity was obtained in 6% and 9%, respectively, of each group. A family history of hot water epilepsy was found in 15% of group 1 and 7% of group 2. A family history of non-reflex epilepsy was obtained in 12% and 28%, respectively, and febrile convulsions (121210) were present in 11% and 7%, respectively. Most developed the disorder before age 10 years, and about 50% had remission or improvement after 3 years. Sixteen of the patients in group 1 developed non-reflex epilepsy as well.

De Keyzer et al. (2005) reported a 10-month-old Belgian boy with hot water epilepsy. About 1 minute after immersion in a warm bath, he had sudden activity arrest, with glazed-eye staring, unresponsiveness, hypotonia, and pallor, followed by cyanosis and postictal drowsiness. The episode lasted about 1 minute, and clonic movements were not seen. Ictal EEG showed focal, temporal, unilateral, rhythmic slow wave activity of high amplitude.

Kaplan et al. (2009) reported a Turkish family in which hot water epilepsy affected 7 individuals spanning 6 generations. One branch of the family showed consanguinity. Three patients had other types of seizures as well, and 2 had a history of febrile seizures. Onset of the hot water seizures ranged from 6 to 14 years. Hot water seizure types included simple partial, complex partial, generalized convulsions, and secondary tonic-clonic seizures. Brain MRI of 3 patients showed cerebral lesions consistent with ischemic gliosis, possibly a permanent effect of hot water seizures.

Ratnapriya et al. (2009) reported 6 Indian families with hot water epilepsy. The largest was a 4-generation family ascertained by the proband who was diagnosed at age 15 years. All had a history of seizures precipitated by hot water baths. In southern parts of India, there is a common cultural custom of taking hot water baths following copious application of warm oil on the head. Hot water of 40 to 45 degrees Celsius was sufficient to trigger seizures. Affected individuals reported sensations of pleasure during bathing, leading to seizures. Routine brain MRI did not show structural abnormalities, but SPECT scanning showed ictal hypermetabolic state in the medial temporal lobe and hypothalamic areas with spread to opposite areas. In the proband from the largest family, interictal EEG showed generalized discharges arising from the left temporal region of the brain.

Inheritance

Ratnapriya et al. (2009) reported 6 Indian families in which hot water epilepsy showed autosomal dominant inheritance with incomplete penetrance.

Mapping

By genomewide linkage analysis of a large 4-generation Indian family with HWE, Ratnapriya et al. (2009) identified a locus on chromosome 10q21 (maximum 2-point lod score of 3.17 at D10S412). Three out of 5 additional families with the disorder showed linkage to the same chromosomal region, yielding a maximum 2-point lod score of 4.86 at D10S412, with a penetrance of 60%. A 15-Mb (21-cM) candidate interval on chromosome 10q21.3-q22.3 was defined by D10S581 and D10S201. Sequence analysis of functional candidate genes revealed no potentially pathogenic mutation.

Population Genetics

Hot water epilepsy is especially common in south India and has been estimated to account for 6.9% of all epilepsies in this region, with a prevalence rate ranging from 60 per 100,000 to 255 per 100,000. Satishchandra (2003) noted that washing of the head in south India is usually done once every 3 to 15 days. Water is usually collected in a bucket and poured over the head and body using a mug. Individuals with hot water epilepsy may also have seizures when in hot showers or baths, as reported in cases from New Zealand, U.S., Canada, U.K., Australia, Japan, and Turkey. Males tend to be more affected than females (2 to 2.5:1).