How Meningitis Is Diagnosed

Meningitis is a condition whose prognosis is conditioned by the speed of its diagnosis. Let's find out what options are available to detect it.
How Meningitis Is Diagnosed

Last update: 28 July, 2021

Meningitis is a disease that causes hundreds of thousands of deaths each year. The chances of a full recovery are conditioned by how quickly it’s detected and its respective treatment is started. In children, older adults, and people with a weak immune system, there are more complications, and so the early diagnosis of meningitis is very important in order to improve the prognosis.

Although the disease is more common in countries in Africa and Asia, as the World Health Organization (WHO) reminds us, in theory anyone can develop it. Let’s see how we can detect meningitis and what else could cause the symptoms when the results are negative.

Diagnosis of meningitis by laboratory tests

Diagnosis of meningitis includes laboratory studies
Laboratory studies (analysis of cerebrospinal fluid, blood, or microbiological studies) aren’t only useful for diagnosing meningitis, but also its causes.

Meningitis is caused by a variety of pathogens. Viruses, bacteria, parasites, and fungi can cause an inflammation of the meninges. It’s also possible for meningitis to occur without these elements, as some conditions such as cancer or rheumatoid arthritis can cause it.

The diagnosis of meningitis isn’t only intended to detect this inflammation, but also to determine what’s causing it. The latter is very important, as the treatment chosen by the specialist differs depending on the cause. As a result, the following laboratory options are available for this:

Lumbar puncture

Lumbar puncture is one of the main methods used when carrying out the diagnosis of meningitis, despite it being an invasive test with possible associated complications.

The procedure consists of extracting a sample of cerebrospinal fluid to determine if there’s inflammation in the meninges and what’s causing it.

Evidence suggests that up to 40% of cases with fungal meningitis (specifically Cryptococcus) can have normal results. This is why it has to be supplemented with other tests if all the symptoms point to meningitis.

Blood tests

Blood tests are very useful in determining bacteria or parasites present in the body (or signs of their presence). An example is a blood culture, a test that shows the growth of bacteria in a medium rich in nutrients.

It’s a cheap, non-invasive alternative that helps reinforce suspicions of the disease. Blood tests can also determine if the disease has led to sepsis.

Diagnosis of meningitis by imaging tests

Imaging tests allow us to determine if there’s inflammation in the meninges, although, by themselves, they aren’t useful in diagnosing the cause behind it. Those used by specialists are the following:

  • Chest X-ray: Sometimes meningitis is the result of other infectious processes, such as pneumonia or tuberculosis. Radiography is helpful in ruling out or confirming these problems, thereby increasing suspicions of their possible triggers.
  • Computed tomography: This allows us to detect structural abnormalities in the brain that explain the causes or complications of meningitis.
  • MRI: This is used to rule out other underlying complications. It focuses on the spinal area, but it can provide clues regarding the inflammation of the meninges.

These three tests, along with the previous ones, are used together to determine the possible presence of meningitis. Of course, the specialist will also carry out a general assessment of the patient, including their habits, development of symptoms, recent trips, and others to determine the possible contexts in which they could have caught the infection.

As we have already indicated, some previous conditions can motivate the inflammatory process. If the patient has been diagnosed with any of the aforementioned conditions, they have a greater probability of developing meningitis in the course of the evolution of their disease.

Differential diagnosis of meningitis

Diagnosis of meningitis includes MRI
Once the laboratory studies have been carried out, it’s a good idea to perform some imaging techniques. These allow you to determine possible causes of meningitis or to make differential diagnoses.

During the diagnosis of meningitis, doctors can rule out other explanations in accordance with the symptoms displayed by the patient. Many conditions appear with similar characteristics, but the most common are the following:

  • Migraines: Bacterial meningitis with complications identical to migraine have been reported. Sometimes this can be the actual diagnosis. It can cause sensitivity to light or sounds, nausea, and dizziness, signs that often accompany meningitis as well. There’s no specific cure, but it can be treated very effectively.
  • Low blood pressure: Hypotension causes dizziness, headaches, fatigue, blurred vision and lightheadedness. It isn’t uncommon for a patient to mistake these for a condition caused by an infection or a problem originating in the brain.
  • Encephalitis: Encephalitis and meningitis are two closely related conditions, as the evidence indicates. They share catalysts in common and their symptoms are nearly identical. However, encephalitis is diagnosed when inflammation occurs throughout the brain.
  • Brain abscess: A brain abscess is a lesion characterized by having a cavity filled with pus. Studies indicate that both this and meningitis have the same infectious triggers.
  • Hemorrhages in the brain: Hemorrhages in the brain occur when a blood vessel ruptures, most of the time caused by an increase in blood pressure or trauma. Its mortality rate is very high and sequelae in recovered patients are very common.

Final recommendations

Strokes, tumors, seizures, systemic infections, and muscle contractures may also explain the symptoms. Keep in mind that meningitis can develop after trauma or surgery, so this should be taken into account during the diagnostic process.

As soon as its presence has been determined as well as the possible agent that’s causing it, treatment will begin. This varies according to the pathogen or the processes that have caused the inflammation.

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  • Lampl, C., Yazdi, K., Buzath, A., & Klingler, D. Migraine-like headache in bacterial meningitis. Cephalalgia. 2000; 20(8): 738-739.
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