Influenza - Neuropsychiatric Manifestations and Complications

Introduction:

Influenza is a virus that causes an infectious disease called flu. There are three types of influenza viruses. They are influenza A, influenza B, and influenza C. Type A of the influenza virus is more virulent and causes severe disease. Sometimes, these viruses may affect other species, like birds, and cause outbreaks in domestic poultry or human influenza pandemics. Apart from respiratory infection, it may also cause neurological manifestations.

What Is Influenza (flu)?

The influenza virus causes flu. It causes respiratory infections and may lead to many complications. Its symptoms include headache, body pain, fever, sore throat, and respiratory symptoms. These symptoms may be severe. It spreads fast through droplets of cough and sneezes, which contain viruses. It can affect people of any age group. Flu may cause complications like pneumonia and bronchitis. These may lead to hospitalization and death.

Influenza is very common. Despite treating the condition well, many individuals face complications from this condition. Among those affected, mental and behavioral changes are observed.

What Are the Neuropsychiatric Manifestations of Influenza?

Karl A Meninger was the first researcher who linked influenza and neuropsychiatric manifestations in 1918. It was the Spanish flu, and this pandemic was also linked to Parkinsonism.

There are two types of neuropsychiatric manifestations of influenza.

1) Acute Manifestations:

The reports of acute manifestations of neurological syndromes have been present since 1385. These manifestations of neuropsychiatric are severe and may lead to death.

• Influenza-associated encephalitis or encephalopathy (IAE).

• Seizures.

• Reye's syndrome (RS).

• Acute necrotizing encephalopathy.

• Transverse myelitis.

• Aseptic meningitis.

• Guillian-Barre syndrome (GBS).

• Acute encephalitis.

One of the studies showed seizures, changes in mental status, and mutism.

Another study by Toovey found that febrile seizure was the most common manifestation, whereas IAE was a less commonly found manifestation of influenza. They also noticed that febrile seizures and abnormal behaviors were found among mild cases of influenza, whereas decreased consciousness to coma was found in severe cases of influenza.

The study also found that influenza can trigger many central nervous system diseases like,

• Encephalopathy of RS.

• Peripheral neuropathy of GBS.

• Klleine-Levin Syndrome.

• Post encephalitic Parkinson's disease.

• Multiple sclerosis.

2) Chronic Manifestations:

These manifestations were seen in schizophrenia, Parkinson's disease, Alzheimer's disease, and mental retardation.

• Parkinson's Disease (PD): The link between Parkinsonism and influenza was reported in 1918. The affected individuals showed decreased mobility and other neurological symptoms of PD.A recent study showed a loss of dopaminergic neurons and persistent inflammation in the brain among those affected with the influenza virus. When the study was done on mice, they developed tremors and difficulty in movements when infected with influenza, a PD symptom. There has been no report of PD among humans due to influenza to date. Another study has found that bird flu may trigger PD. Influenza antigens can be demonstrated in Encephalitis lethargica ( EL) patients, and there may be a possibility of EL recurring in the influenza pandemic.

• Schizophrenia: A study has shown mental disturbances among individuals affected with influenza. Studies have shown that children born during winter and early spring were affected more by schizophrenia. This may be due to influenza infections expected to occur more in these seasons. Many Studies have shown the link between schizophrenia among those children of women affected with influenza during pregnancy. Many researchers have found an inherent immunological distortion of the mind among those infected with the influenza virus.

• Dementia and Mental Retardation: According to a study, there was dementia and disturbance in gait observed among those affected with influenza. Another study showed the link between mental retardation ( MR) and influenza infection among those children born to women who were affected during pregnancy, especially 3rd and 4th month of pregnancy

• Mood Disorders: Another case reported an association between mania and influenza. Those affected with influenza show similar symptoms of depression. Hence they have found a relationship between mood disorders and influenza infection. It was also found that unipolar affective disorders were found among those affected by influenza.

What Are the Neurologic Complications of Influenza?

Influenza causes many neuropsychiatric complications. Delirium and abnormal behaviors are seen among children and adolescents. They show varying degrees of delirium and anxiety. Some of them may also show hallucinations.

Influenza may cause major syndromes like the following -

• Acute Necrotizing Encephalopathy( ANE): This syndrome may lead to the death of an individual. It shows multiple brain lesions and affects many organs of the body. This may lead to disseminated intravascular coagulation and multiple organ failure. This may be due to increased cytokine production due to inflammatory responses.

• Acute Encephalopathy with Biphasic Seizures and Late Reduced Diffusion ( AESD): This condition was due to excitotoxicity, febrile infection, and genetic predisposition. In this condition, delayed death of cerebral cortical neurons occurs. It is

• Clinically Mild Encephalitis/Encephalopathy With a Reversible Splenial lesion ( MERS): This syndrome involves delirium, seizures, and stupor. This condition is most common among children.

• Febrile Delirium: It is most common among children. This is characterized by impairment in consciousness, fear, anxiety, disorientation, and hallucination. These symptoms may last for several minutes or hours.

• Delirium with Rushing/Jumping Behavior: According to a study, some show abnormal behavior, like jumping from a raised apartment. This type of behavior was also observed in influenza infection.

• Reproducible Neuropsychiatric Adverse Effects of Oseltamivir: Oseltamivir is a drug used to treat influenza. Neurological manifestations may also be caused due to the treatment of it by drugs or may be due to the infection itself also. Abnormal behavior and hallucinations were observed among children treated with Oseltamivir.

Conclusion:

Influenza or flu is a common infectious disease due to the influenza virus. Along with the common symptoms, it may also cause neuropsychiatric manifestations. Hence, knowing about influenza, its symptoms, and neurological manifestations is important. Knowing helps in identifying the symptoms early. Early diagnosis help achieves effective treatment. This, in turn, helps to have a good quality of life.