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Summary: Purpose: To clarify duration of postictal psychosis (PIP) episodes and identify factors that influence its duration.
Methods: Fifty-eight patients with epilepsy exhibited 151 PIP episodes during a mean follow-up period of 12.8 years. Distribution of the duration of these episodes was determined, and factors potentially affecting were analyzed. Factors analyzed included PIP-related variables (i.e., antecedent seizures and the lucid interval) and patient characteristics (i.e., type of epilepsy, lateralization of EEG abnormalities, and intellectual functioning).
Results: The mean duration of the 58 first PIP episodes was 10.5 days, and that of all 151 PIP episodes (including multiple episodes) was 9.2 days. Approximately 95% of the PIP episodes resolved within 1 month. Most PIP-related variables, except for antipsychotic drugs administered, were not associated with duration of the episodes. Several patient characteristics, i.e., history of interictal psychosis, family history of psychosis, and intellectual functioning, were associated with duration of the PIP episodes.
Conclusions: This study showed that most PIP episodes last less than 1 month. PIP episodes appear to be prolonged when individuals have an underlying vulnerability to psychosis. Clinical phenomena that can trigger PIP may not determine the course of the PIP episode.
Postictal psychosis (PIP) is a condition that follows an increased seizure frequency or intensity in epilepsy patients (Logsdail and Toone, 1988; Lancman et al., 1994; Kanemoto, 2002). Several studies have shown various risk factors for development of PIP, i.e., advanced age at the time of the episode (Adachi et al., 2002), the type and frequency of antecedent seizures (Devinsky et al., 1995; Umbricht et al., 1995; Kanemoto et al., 1996a), bilateral EEG abnormalities (Savard et al., 1991; Devinsky et al., 1995; Umbricht et al., 1995), and decreased intellectual functioning (Adachi et al., 2002).
Although many PIP episodes are self-limited in nature, some episodes evolve into disturbing or prolonged psychotic symptoms, necessitating the administration of pharmaceutical or behavioral treatment (Kanemoto, 2002; Adachi, 2005; Akanuma et al., 2005). However, few studies have shown the frequency of such prolonged episodes among all PIP episodes. Lack of evidence on its time course has prevented us from full understanding of the nature of this event.
Another important, but not yet addressed entirely, issue is whether any clinical variables are associated with the duration of the episode. Although several clinical variables and patient characteristics have been investigated as risks for the development of PIP episode (Savard et al., 1991; Devinsky et al., 1995; Umbricht et al., 1995; Kanemoto et al., 1996a; Adachi et al., 2002) as mentioned earlier, whether these factors also affect the duration of PIP episode remains a question. If we know factors related to the duration of PIP, we can estimate the course of each PIP episode more precisely and optimize our treatment strategies.
In the current study, we investigated 151 PIP episodes to reveal its distribution of the duration and factors that are related to the duration.
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Of the 151 PIP episodes we studied, 72 (47.7%) lasted 5 days or less and 146 (96.7%) resolved within 1 month. These percentages are concordant with previous observations of PIP with either natural or induced seizures (Savard et al., 1991; Lancman et al., 1994; Kanner et al., 1996; Kanemoto, 2002). Our results support empirical data that PIP episodes generally last less than 1 month. The PIP episodes lasting more than 1 month appear to be exceptional (Akanuma et al., 2005).
Most PIP-related variables did not correlate with duration of the PIP episodes. The number and types of antecedent seizures, although essential to the occurrence of PIP, did not affect the overall course of the episodes. Neither presence nor duration of a lucid interval, a phenomenon unique to PIP and that may play a role in the PIP process (Kanemoto, 2002), was also associated with duration of the episodes. Although a high frequency of habitual seizures and increased number of AED administered often reflect intractability of epilepsy, these factors did not prolong the PIP episodes. These findings suggest that antecedent seizures and particular epilepsy-related variables act as triggers of PIP without influencing its successive course. Thus, once the PIP process starts, other variables, later described, may regulate the course of the episode.
Of the PIP-related variables we studied, only the condition of APD administration correlated significantly with the duration of PIP, although the administration of APD may not simply reflect the nature of PIP episode. Duration of the PIP episodes was shortest in the non-APD group, suggesting that many PIP episodes would resolve naturally even without APD treatment. Some researchers have recommended mild sedation without the use of APDs as optimal treatment for PIP (Lancman et al., 1994). In contrast, PIP episodes were longest in the APD add-on group. These episodes continued for 9.5 days even after the administration of APDs, and were as long as episodes in the APD group. This may be partially due to the doctors' tendency to prescribe APDs in difficult cases, i.e., violent, recurrent, or prolonged PIP episodes. Prospective case-controlled studies might clarify the relation between the distinct effects of APDs on PIP and the intractability of some PIP episodes.
Several patient characteristics were significantly associated with the duration of PIP, even though in patients who experienced multiple PIP episodes, the duration of each episode differed. First, PIP episodes were longer in patients with bimodal psychosis than in patients with PIP alone. This is in line with our reported findings in four patients with interictal-antecedent bimodal psychosis (Adachi et al., 2003). Patients with bimodal psychosis often show characteristics associated with both postictal and interictal psychoses (Tarulli et al., 2001; Adachi et al., 2002, 2003). Second, PIP episodes tended to be longer in patients with subnormal intellectual functioning. Impaired intellectual functioning is a risk factor for development of PIP or interictal psychosis (Adachi et al., 2002). Premorbid cognitive function is generally a prognostic factor in patients with psychosis (Malla and Payne, 2005). Psychotic symptoms in schizophrenia patients with learning disability are generally more concrete and less elaborate (Reid, 1982). Last, PIP episodes were longer in patients with a family history of psychosis than in those without. This is consistent with studies on functional psychosis that have shown poor outcomes in patients with a family history of psychosis (Verdoux et al., 1996; Bromet et al., 2005). These patient characteristics likely reflect an underlying increased vulnerability to psychosis. In addition to precipitating a PIP episode, they may delay its resolution.
Our study requires some considerations. First, due to the fact that our consultants were doubly qualified in psychiatry and epileptology, there may have been a selection bias toward patients with intractable or complicated epilepsy. Patients are not often referred to a specialist clinic until their PIP episode causes serious behavioral or social problems. Second, we excluded PIP episodes lasting less than 12 h because it is very difficult to identify short-lasting PIP episodes. These easily go unnoticed or unreported in outpatient settings. Using video-EEG monitoring systems, Kanner et al. (2004) showed that approximately 40% (three of seven patients) had PIP episodes lasting 24 h or less. If we could detect PIP episodes lasting less than 12 h precisely, the distribution of PIP episodes might have shifted toward a shorter duration. Third, some variables that may affect duration of PIP, such as whether the patients had sufficient repose and sleep (Lancman et al., 1994; Kanemoto, 2002) were not analyzed in our study. Last, although PIP episodes often show a variety of psychopathological features, this study did not evaluate them in a systematic manner. Further work is necessary to investigate whether certain psychopathologies can be associated with duration of PIP.
In conclusion, we found that most PIP episodes resolve within 1 month. PIP episodes appear to be prolonged when patients have an underlying vulnerability to psychosis. Clinical phenomena that trigger a PIP episode may not determine the course of the episode. Our findings on the duration of PIP would contribute to further development of evidence-based treatment strategies.