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Encephalopathy isn’t a distinct disease, but rather refers to a syndrome of diffuse brain dysfunctions, which may be associated with a variety of causes.
Viral and bacterial infections are among the common culprits, but encephalopathy may also be caused by trauma, prions, toxic chemical exposures, and even a thiamine deficiency (Wernicke’s Encephalopathy).
The overriding hallmark of encephalopathy is an altered mental state, although depending and severity of encephalopathy, common neurological symptoms such as progressive memory loss and changes in cognitive ability, personality changes, inability to concentrate, lethargy, and loss of consciousness may be seen.
In recent years Influenza has been seen as a rare cause of encephalopathy.
In an eMedicine article on Influenza by Robert W Derlet, MD, Professor of Emergency Medicine, University of California at Davis School of Medicine encephalopathy is listed under clinical presentation:
Acute encephalopathy has recently been associated with influenza A virus. In a case series of 21 patients, Steininger et al described clinical, CSF, MRI, and EEG findings.4 Clinical features included altered mental status, coma, seizures, and ataxia. Of those who underwent further testing, most had abnormal CSF, MRI, and EEG findings.
The CDC’s MMWR (July 23rd issue) reported on 4 pediatric patients with the novel H1N1 virus who presented with neurological symptoms including unexplained seizures and altered mental status.
Neurologic Complications Associated with Novel Influenza A (H1N1) Virus Infection in Children --- Dallas, Texas, May 2009
Neurologic complications, including seizures, encephalitis, encephalopathy, Reye syndrome, and other neurologic disorders, have been described previously in association with respiratory tract infection with seasonal influenza A or B viruses (1--2), but not with novel influenza A (H1N1) virus.
On May 28, 2009, the Dallas County Department of Health and Human Services (DCHHS) notified CDC of four children with neurologic complications associated with novel influenza A (H1N1) virus infection admitted to hospitals in Dallas County, Texas, during May 18--28.
And as previously mentioned, even seasonal influenza has been linked to very rare neurological symptoms. The editorial note from the MMWR stated that:
Considering that clusters of influenza-associated encephalopathy in children have been reported during previous community outbreaks of seasonal influenza (1--2) and that children appear to be infected with novel influenza A (H1N1) virus more frequently than adults (3), additional neurologic complications in children are likely to be reported as the pandemic continues.
Clinicians should consider influenza associated encephalopathy in the differential diagnosis of children with ILI and seizures or mental status changes, and remain aware of the potential for severe neurologic sequelae associated with seasonal or novel influenza A (H1N1) virus infection.
The incidence of neurological involvement with most influenza viruses appears to be quite low, although obviously not unheard of.
Earlier this month, Children's Hospital of Pittsburgh reported 5 kids with encephalitis over the past 6 weeks.
Today we learn via the Daily Yomiuri Online that a surprising number of H1N1 patients in Japan have presented with encephalopathy since July.
In a normal year, Japanese health officials say they might see 40 to 50 such cases – but in the past four months they’ve seen more than twice that many.
A hat tip to Treyfish on FluTrackers for posting this link.
132 flu patients hit with brain disorders since July
The Yomiuri Shimbun
A total of 132 influenza patients in Tokyo and 27 prefectures have developed encephalopathy, or swelling of the brain, since July, according to the National Institute of Infectious Diseases.
Normally, only about 40 to 50 seasonal flu sufferers develop encephalopathy each year, meaning the latest figure has already more than doubled in four months since the new strain of flu began spreading.
Encephalopathy occurs when viruses cause the immune system to overreact, resulting in a swelling of the brain.
Though the ages of the 132 people in question range from 1 to 67, most were under 15.
By age, 7-year-olds constituted the largest group, with 22 sufferers. This is older than the average age for encephalopathy sufferers, who are most often aged between 1 and 3.
Further examination of 60 of the 132 patents revealed consciousness-related malfunctions.
The period over which these malfunctions occurred following the initial fever ranged from one day for 12 people, two days for 36 people, and four days for eight people.
The examination reconfirmed that in many cases, the serious symptoms occurred in the early stages of the disease.
Of 59 patients whose symptom development had ended, three, or 5 percent, died. Seven, or 12 percent, suffered aftereffects such as physical paralysis or mental or nerve disorders.
Forty-nine, or 83 percent, fully recovered.
Nobuhiko Okabe, chief of the institute's Infectious Disease Surveillance Center, said: "If a patient exhibits such symptoms as slow responses or saying strange things, encephalopathy could be the cause. In such cases, patients should see a doctor immediately."
(Nov. 24, 2009)
