Hot water epilepsy: clinical and electrophysiologic findings based on 21 cases.

PURPOSE: Our aim is to outline the clinical and electroencephalographic (EEG) features of patients with hot water epilepsy (HWE), a rare and unique form of reflex epilepsy.

METHODS: Twenty-one patients with HWE, seen in our clinic until 1999, were studied. Male outnumbered female subjects in a ratio of 3:1. The age at the onset of seizures ranged from 19 months to 27 years (mean age at onset, 12 years).

RESULTS: The main factors precipitating seizures were bathing with hot water and/or pouring water over the head. Six patients reported self-induction, either by increasing the heat or the amount of water and/or recalling earlier bathing experiences. Nine patients expressed feeling pleasure during the seizures. Twenty patients had partial seizures, eight of whom also had secondarily generalized seizures. One patient had apparent generalized seizures only. Spontaneous seizures were present in 62% of the cases. Interictal epileptogenic abnormalities were documented in the EEGs of eight patients; the other eight had normal EEGs. The major sites of epileptogenic activity were over the unilateral temporal regions (in 40% of patients). Neuroimaging studies available for 12 patients (four cranial computed tomography and eight cranial magnetic resonance imaging scans) revealed normal findings. Seizure control in patients who were followed up was achieved by reducing the temperature or the duration of the bath or shower; several of the patients required medication.

CONCLUSIONS: The major findings of this study are that HWE has a male preponderance, can be self-induced, is often done for pleasure, has complex triggering factors, and shows temporally located abnormalities in the EEGs. Although HWE is generally known to be self-limited, antiepileptic drug treatment may sometimes be necessary to control seizures. Hot water epilepsy should be classified separately among the epileptic syndromes.