By Barry C. Fox, M.D., University of Wisconsin
Infections of two different organ systems, the respiratory tract and central nervous system have an unusual common thread. In some cases, an infection can start in the respiratory tract, but it can end up in the region of the brain, causing infections that can result in death. And there are other conditions that can pose a danger to the central nervous system.
Let’s look at some.
Bacterial Infections
Normal bacteria colonize the back of the throat and usually don’t cause any mischief. One of these is called Streptococcus pneumonia, or Strep pneumo for short. In fact, the most common pneumonia in adults is, in fact, Strep pneumo. The germ has several means to elude our normal defenses, especially a very thick sugar capsule that makes it difficult for our macrophages to swallow the bacteria.
Now, let’s assume a hypothetical patient who has had a silent aspiration event approximately 48 hours before becoming ill. If Strep pneumo gets past the upper and lower respiratory defenses, it will cause pneumococcal pneumonia. By now, the bacteria are fiercely multiplying at the alveolar space. After a certain number of critical bacteria are reached, our patient becomes ill with fever, increased difficulty breathing, and a cough.
Medical X-rays
At this point, the patient will likely seek medical attention. A chest x-ray will be abnormal with a white zone that defines the pneumonia. Now, if medical attention is sought at this point in time, there’s probably a good chance that the infection can be managed with supportive care and appropriate antibiotic targeting pneumococcus.
Patients can usually be discharged home with careful medical follow-up with a mortality rate of only one percent. Sometimes, depending on the severity of illness, the patient’s age, and social factors, hospitalization may be required. The mortality rate for patients hospitalized with community-acquired pneumonia increases to 12 percent.
Learn more about milestones in infectious disease history.
Worsening Situation
Now, let’s say instead of seeking medical attention, our patient is more stubborn and won’t listen to the advice of family members and friends, or they live alone without frequent contacts with others. It’s likely that the infection will become more severe, and develop into a body-wide, systemic infection.
Now, the situation can get even worse. As the pneumococcus creeps out into the bloodstream, it initiates a more advanced inflammatory process called sepsis. Now the mortality rate has climbed to 40 percent. Additionally, the pneumococcus has the propensity to attack the linings around the brain and the spinal cord, causing a condition known as bacterial meningitis, and this is precisely what happens to our patient.
This is a transcript from the video series An Introduction to Infectious Diseases. Watch it now Wondrium.
The Head and Brain
Let’s take a closer look at the anatomy of the head, so you can understand where the central nervous system infections like this reside. The outside head bone is the skull, and there’s a membrane barrier located just beneath it, called the meninges. Cerebrospinal fluid totally surrounds the brain, protecting it from injury and is contained by the meninges.
Inflammation of the meninges is referred to as meningitis. If the actual nerves of the brain or spinal cord become infected, the condition is known as encephalitis, or myelitis. With meningitis, since the fluid is a normally sterile body site, a rapid and significant inflammatory response occurs.
Meningitis
The white blood cells and other chemical mediators of inflammation, or cytokines, also migrate into the spinal fluid, where a major battle begins between the bacteria and the body’s immune system. One of the consequences of this battle is increased water pressure on the brain and spinal cord, and this leads to impairment in our patient’s ability to communicate, and if severe enough, an actual coma.
When the infection reaches this dangerous threshold, our patient’s life is certainly in jeopardy. Most conditions, which cause fever, headache, and a stiff neck—symptoms of meningitis—are not due to bacterial causes and are usually not life-threatening.
Aseptic Meningitis
This medical condition is known as aseptic meningitis, and the main cause is usually the result of a viral infection, and while it may not be as severe as bacterial meningitis, it can still make you feel miserable for five to seven days.
Eighty percent of aseptic meningitis is caused by enteroviruses. The root of the word ‘entero’ means intestinal. And these viruses cause intestinal symptoms to begin with but then travel through the bloodstream to the meninges, where they can cause meningitis.
Fortunately, our body is usually able to overcome the viral infection without serious consequences. There are no antiviral medications that can be used for most viral meningitis, and vaccination efforts are only beginning for enteroviruses.
Learn more about how vaccines save lives.
Encephalitis
On very rare occasions, the virus can actually invade the brain tissue causing encephalitis, and the illness is more severe with signs of altered consciousness or coma. One of the animal, or zoonotic, infections transmitted from robins to mosquitoes to humans, known as West Nile virus, can cause encephalitis.
Herpes simplex viruses that usually move forward and cause fever blisters can travel backwards towards the spine and cause aseptic meningitis, or less commonly encephalitis.
Finally, aseptic meningitis can also occur from some of the tick-borne diseases, especially the Lyme spirochete, Borrelia burgdorferi. So if you have a tick bite, and you have a severe headache and a stiff neck, it is most likely that you have aseptic meningitis.
Warnings of Brain Infection
It’s very important to know the symptoms of infections around the brain and spinal cord so you can act quickly. The need for medical attention should not be minimized. Although the odds are in your favor that an unusually severe headache is not life threatening, you should not make that determination on your own.
Always seek medical attention for a complex of symptoms that includes fever, a severe headache, irritation of vision with bright lights, and a stiff neck or a stiff back.
Common Questions About Meningitis and Encephalitis
In extreme cases of pneumococcus infection, the pneumococcus creeps out into the bloodstream. Additionally, the pneumococcus has the propensity to attack the linings around the brain and the spinal cord, causing a condition known as bacterial meningitis.
There’s a membrane barrier located just beneath the skull called the meninges. Cerebrospinal fluid totally surrounds the brain, protecting it from injury and is contained by the meninges. Inflammation of the meninges is referred to as meningitis. With meningitis, since the fluid is a normally sterile body site, a rapid and significant inflammatory response occurs.
Most conditions, which cause fever, headache, and a stiff neck—symptoms of meningitis—are not due to bacterial causes and are usually not life-threatening. This medical condition is known as aseptic meningitis, and the main cause is usually the result of a viral infection. Eighty percent of aseptic meningitis is caused by enteroviruses.
If the actual nerves of the brain or spinal cord become infected, the condition is known as encephalitis, or myelitis. Virus can actually invade the brain tissue causing encephalitis, and the illness is more severe with signs of altered consciousness or coma. West Nile virus and Herpes simplex viruses can cause encephalitis.
