Febrile seizure (FS) patients in a one-year period, 2003-4, during an outbreak of influenza A in the Kitakawachi area of Japan, were prospectively analyzed by researchers at Hirakata City Hospital and Osaka Medical College. Influenza patients (n=47, 22%) and noninfluenza patients (n=168) with FS were compared with regard to clinical features of FS. Only one patient in this period had influenza B. Influenza virus infection was confirmed by rapid antigen test and/or serologically. One or more features of complex FS were exhibited in a total of 71 (33%) patients. Postictal impairment of consciousness was prolonged for more than 30 min (PPIC) in 28 (13%) patients. None had evidence of other intracranial pathology or symptomatic seizure etiology. Associations of influenza A with complex FS (prolonged, partial, multiple seizures) and PPIC were analyzed by multiple logistic regression. PPIC occurred more often in influenza than in non-influenza patients (10/47 [21%] vs 18/168 [11%], P=0.057). The influenza A group was significantly older than non-influenza FS patients: 40+/-22 vs 27+/-17 months, P<0.001. Influenza A was independently associated with PPIC (P=0.006), but not with other atypical features of the complex FS. Partial FS was more common in older patients, those with a past history of FS, and patients with a significantly lower body temperature at seizure occurrence (39.29+/-0.61C vs 39.57+/-0.61C, P=0.032). PPIC was associated with a higher body temperature at seizure occurrence (39.80+/-0.65C vs 39.46+/-0.60C, P=0.011), intravenous administration of diazepam (9/28 [32.1%] vs 4/187 [2.1%], P<0.0001), and prolonged seizure (10/28 [35.7%] vs 5/187 [2.7%], P<0.0001). [1]

COMMENT. An almost identical study and similar findings to those in Japan are reported from Hong Kong [2]; see Ped Neur Briefs Dec 2006;20:94-5).

In the Japanese study, FS were complex in one third of the influenza-associated seizures, and postictal impairment of consciousness was prolonged (PPIC) for more than 30 min in 13%. Children with FS generally recover consciousness in less than 30 min. If recovery of consciousness takes > 1 hour, an acute symptomatic etiology should be suspected, according to a recent UK report [3]; Ped Neur Briefs Jan 2007;21:4). In the simultaneous Japanese report, none of the influenza FS patients had evidence of encephalitis or structural brain lesion. However, many had complex FS, and PPIC was associated with prolonged seizure and with the need for administration of diazepam. Those with partial FS had a lower body temperature, indicative of a lower FS threshold [4]. Patients with a higher body temperature had PPIC and had received diazepam, given to raise the seizure threshold. A significant factor for development of FS in influenza is a coexisting gastroenteritis (Kwong KL et al. Ped Neur Briefs Dec 2006;20:94-5), a cause of afebrile seizures with focal onset, as described in the following article.