In this article, we reported an 8-year-old pediatric patient with micturition-induced reflex epilepsy. So far, only a dozen cases of micturition-induced RS have been reported in literature. Based on a review of all the published cases [2,3,4,5,6,7,8,9,10,11,12,13,14], the main features of micturition-induced RS include: (1) a rather low prevalence, with an onset predominantly in childhood, but affecting both sexes equally; (2) common co-existence of developmental delay in cases; (3) concomitant occurrence of spontaneous seizures in nearly 70% of these patients, often preceding the micturition-induced RS; (4) the most common features of clinical semiology include, in a descending order of frequency, posturing of the upper limbs, deviation of the head and eyes, automatism, and a lack of awareness; (5) the true epileptic focus is not clearly identified, but the onset is likely to be from the midline region; and (6) prognosis generally satisfactory, as half of the cases achieved adequate seizure control with anti-seizure medication.
RS induced by micturition seems to have a young age of onset, except one case who showed onset age of 18 years. In contrast, RS associated with other triggers seems to typically have an onset in the second decade of life [15]. The majority of patients with RS induced by micturition present normal structural neuroimaging features, but a common documented history of developmental delay. This suggests that the micturition-induced seizures may be associated with brain immaturity as well as preexisting neurodevelopmental abnormalities.
In literature, nine cases were reported to have spontaneous seizures preceding the micturition-induced RS [3, 5, 6, 8, 10,11,12,13,14]. Previous studies showed that the majority of patients with RS also suffer from spontaneous seizures, and over 21% of the patients with idiopathic generalized epilepsy experience concurrent RS [16]. Some investigators proposed that RS and spontaneous seizures are two extremities of a conceptual continuum [17]. Changes in structural and functional brain networks occur after spontaneous seizures, resulting in hyperexcitability in certain brain areas, which would become more susceptible to epileptic discharges upon stimulation from a particular sensory, cognitive or motor stimulus [18]. In addition, there were three cases who experienced a seizure-free period from spontaneous seizures to RS, just like our case presented here [5, 11, 13]. This phenomenon has been rarely studied, and the underlying mechanism requires further investigation.
Glass et al. [11] performed ictal single-photon emission computed tomography (SPECT) within 5 s of seizure onset and revealed hyperperfusion in the anterior cingulate gyrus and the right anterolateral frontal lobe. Another ictal SPECT study revealed significantly increased perfusion in the mesial frontal regions [8]. These areas were close to or directly overlapping with the areas activated by urinary function [19]. Similarly, Cvetkovska and colleagues [12] reported focal cortical dysplasia in the right middle frontal gyrus, which overlapped with the brain regions activated by urinary function. Based on these findings, we speculate that the mechanism of micturition-induced RS may involve excessive excitation of regions that participate in micturition, as these regions would be more susceptible to epileptic discharges triggered by the physiological voiding process and, therefore, more prone to seizures during urination.
The exact epileptic focus of micturition-induced RS has not been clearly identified. Several reported cases assessed by ictal EEG showed a central epileptogenic focus [2, 3, 5, 6, 10, 11, 14], while others had no clear focal features. The semiology of micturition-induced RS is characterized by posturing of the upper limbs, deviation of the head and eyes, and automatism, which indicate the involvement of a common neural pathway. As a complex process, micturition is regulated by multiple levels of the central and peripheral nervous systems. The superomedial part of the frontal lobe and the anterior part of the cingulate gyrus control micturition [19]. The supplementary motor area (SMA) is activated during contraction of the pelvic floor muscles, which produces seizure activity, such as tonic posturing involving unilateral or bilateral extremities [20]. In the present study, although an unclear epileptic focus was identified by ictal EEG, we speculate that the SMA is involved in epileptic networks due to the shared clinical features of the reported cases.
