Volume 16, Number 1—January 2010
Dispatch
Acute Encephalopathy Associated with Influenza A Infection in Adults
, Chun Kwok Wong, Paul K.S. Chan, Niklas Lindegardh, Nicholas J. White, Frederick G. Hayden, Edward H.C. Wong, Ka Shing Wong, Clive S. Cockram, Joseph J.Y. Sung, and David S.C. HuiTable 1
Clinical and laboratory findings in 3 patients with acute encephalopathy associated with influenza infection, Prince of Wales Hospital, Hong Kong*
| Clinical and laboratory findings | Patient 1 | Patient 2 | Patient 3 |
|---|---|---|---|
| Age, y/sex | 76/M | 86/F | 72/M |
| Concurrent illnesses | Ischemic heart disease | Diabetes mellitus, hypertension | COPD |
| Influenza vaccination within 6 mo | None | None | None |
| Symptoms on examination |
Fever >38°C, cough, disorientation, incoherent speech, mental dullness |
Fever >38°C, cough, delirious, impaired consciousness, did not follow verbal command |
Fever >38°C, cough, disorientation, agitation, incoherent speech, involuntary 4-limb tremor |
| Focal neurologic sign or meningism | Absent | Absent | Absent |
| Chest radiograph, consolidation | Absent | Absent | Absent |
| Antiviral (oseltamvir) | None | Given | Given |
| Outcome (duration of encephalopathy) | Recovered (2–3 d) | Recovered (3–4 d) | Recovered (6–7 d) |
| Brain CT scan (noncontrast) | Normal | Old ischemic changes; known small, calcified meningioma | Normal |
| Virus isolated from NPA |
Seasonal (H1N1) 2008 |
Subtype H3N2 |
Subtype H3N2 |
| CSF testing results | |||
| Opening pressure, cm H2O | 11 | 9 | 14 |
| Cell count (x 106/L) | 1 | – | 0 |
| Glucose, mmol/L | 4.2 | 7.4 | 3.7 |
| Protein, g/L | 0.46 | 0.47 | 0.16 |
| Virus isolated | None | None | None |
| RT-PCR for H3 and H1 influenza virus | Negative | Negative | Negative |
| Bacterial culture | Negative | Negative | Negative |
| Others | HSV, HZV, and enterovirus PCR negative | HSV, HZV, and enterovirus PCR negative | HSV PCR negative |
*COPD, chronic obstructive pulmonary disease; CT, computed tomographic scan; NPA, nasopharyngeal aspirate; CSF, cerebrospinal fluid; RT-PCR, reverse transcription–PCR; HSV, herpes simples virus; HZV, herpes zoster virus. In all cases, there was no hypoglycemia, and liver and renal function test results were normal. C-reactive protein level was elevated in all cases. For patient 3, an electroencephalogram was performed and showed generalized slowing of background consistent with moderate encephalopathic change (similar to that observed in septic encephalopathy) (1,6). Findings are consistent with previous reports on adult cases of influenza-associated encephalopathy: patients are all unvaccinated, pleocytosis and cerebral imaging abnormalities (even with magnetic resonance imaging) are usually absent, and symptoms are generally self-limiting (1,6). Most reports have mentioned influenza A as a cause of encephalopathy, and more commonly subtype H3N2 (1–6).
