Delirious behavior or mild reduction of consciousness mimicking influenza-associated encephalopathy.

BACKGROUND

During the A/H1N1 pandemic, patients suffered from impaired consciousness. They were suspected of or diagnosed as having influenza-associated encephalopathy (IAE) in an emergency situation. Their symptoms resembled those of a recently described 'unique clinical group', which were reported to have a favorable prognosis.

METHODS

We retrospectively examined 46 patients and divided them into two groups. Group IC contained the 26 patients with persisting impaired consciousness. The remainder of the patients were categorized into group R, consisting of patients with only neurological symptoms without impaired consciousness.

RESULTS

Male predominance (22 male/four female) was noted in group IC. Patient age ranged from 5 to 12 years old (mean ± SD, 7.7 ± 2.3 years). Impaired consciousness such as delirious behavior or mild reduction of consciousness lasted continuously or intermittently from 5 min to 2.5 days. On electroencephalogram, semi-rhythmic high-voltage slow waves in the parieto-occipital regions and diffuse high-voltage slow waves were observed in eight and in two patients, respectively. In group R, there was no gender predominance. Patient age ranged from 1 to 9 years old (mean ± SD, 4.1 ± 2.5 years). All group R patients were clinically diagnosed with febrile seizure.

CONCLUSIONS

Some of the characteristics in group IC resembled those of the unique clinical group, and are part of a continuous clinical spectrum. Some patients may have favorable outcome without specific treatment.