Viruses including influenza A, herpes simplex, herpesvirus 6, and rabies can invade the brain through the nose, according to a report in the September 10, 2011, issue of Science News. Laura Sanders explained that specialized cells help connect nerves in the nasal cavity to the olfactory bulb of the brain. These cells may provide an entry pathway for viruses.
Influenza complications involving the brain can be serious or even fatal. Dr. Alexandra Martin and Dr. Erin Parrish Reade of the University of Tennessee College of Medicine-Chattanooga provided a case report of a 7-year-old girl who died of acute necrotizing encephalopathy associated with H1N1 influenza.
The family refused autopsy, so Martin and Reade noted that it was unknown whether the influenza virus was present in the brain in this patient, or whether the damage was caused by secondary factors. The family reported that the child had not ingested anything toxic, and the only medicine given to her at home was ibuprofen.
“It appears that CNS [central nervous system] sequelae of influenza occur with disproportionate frequency in patients of Asian descent, despite the fact that influenza itself is a very common winter febrile illness in all developed countries,” Martin and Reade wrote.
Their patient was of Chinese descent. As background information, they reported that 18 percent of acute necrotizing encephalopathy cases in Japan are associated with influenza A infection. This illness is not always fatal, but survivors have significant neurological symptoms.
“Although influenza is a relatively benign illness in the majority of healthy children, physicians who care for children in the United States should be aware of ANE [acute necrotizing encephalopathy] and should maintain a high degree of clinical suspicion in any child presenting with acute mental status changes in the setting of influenza infection,” Martin and Reade concluded.
While most patients with neurological complications of the flu are children, adults can also be affected.