How Meningitis Is Diagnosed

Meningitis is a condition that affects the meninges, which are layers of tissue that cover, protect, and cushion the brain and spinal cord. It is diagnosed by identifying an infection or confirming inflammation in the cerebrospinal fluid (CSF) that surrounds the brain and spinal cord.

A variety of exams and tests may be done as part of the diagnostic process, but only a lumbar puncture (LP) can confirm meningitis. Also known as a spinal tap, this is an invasive but largely safe procedure that involves removing cerebrospinal fluid and then analyzing it in a lab.

This article explores why diagnosis really begins with you, as well as what the various exams and procedures that a healthcare provider may perform are.

Self-Checks

You cannot diagnose meningitis on your own. You can't rule it out either.

Immediate diagnosis and treatment for meningitis is important, but that process can only be started if you recognize the signs and symptoms and seek an evaluation promptly.

There are several important signs that you can look out for. Seek medical attention if you or your child experience:

• Severe headaches*
• Stiff or painful neck*
• Fever
• Back pain
  
• Flu-like symptoms
• Rash anywhere on the body
• Nausea or vomiting
• Mental confusion
• Extreme drowsiness
• Eyes sensitive to light
• Seizures

*Together, these symptoms are hallmark characteristics of meningitis.

Glass Test

If you or your child has a rash, especially if it has red or purple spots, press a clear drinking glass firmly against the markings.

If you can still see the markings clearly through the glass, seek urgent medical attention. This can be an indicator of a severe form of meningitis that needs emergency treatment.

Examinations

Your healthcare provider will ask you about your medical history and your symptoms. They will then conduct a physical exam to check for certain signs of meningitis.

Nothing they note can be considered proof of meningitis, but findings can be helpful indicators that more testing is needed. That said, it's also possible that you may have meningitis but no apparent physical signs.

Physical indicators of meningitis that a healthcare provider will look for include:

• Brudzinski's sign: You lie down and your healthcare provider puts one hand behind your head and another on your chest and then gently lifts your head to see if there is involuntary bending of your knees and hips. Another option is to bend one of your legs to see if there is any involuntary bending of the other leg.
• Kernig's sign: You lie down with your leg and hip flexed to form a 90-degree angle. Your healthcare provider will slowly extend your leg at the knee to see if it causes intense pain.
• Nuchal rigidity: Your healthcare provider will see if you can bend your neck, since stiffness of neck muscles can be a sign of meningitis.

If you have a rash, your healthcare provider will examine it and may start treatment if a severe meningitis infection is suspected.

Eye Exam

Your healthcare provider may look at the structures inside your eyes using a tool call an ophthalmoscope, which contains a light and various lenses.

This non-invasive test, known as a funduscopic exam, allows your healthcare provider to see if you have swelling of the optic nerve, a bundle of nerves that carry visual messages. They will also look for any other evidence of inflammation or increased pressure in your eyes, a sign of a severe case of meningitis.

Ear Exam

During an ear examination, your healthcare provider will look in your ear canal.

This examination can show swelling, fluid, redness, or other signs of an underlying ear infection accompanying meningitis, which is more common in children.

If there is fluid draining, it may be sampled and sent to a laboratory for testing to identify infectious organisms.

Labs and Tests

Several tests and diagnostic procedures may follow.

When meningitis is due to an infection, CSF samples may be used to identify the cause.

Viral meningitis is the most common type. Bacterial meningitis is the second most common type. In rare cases, meningitis can also be caused by fungal, parasitic, or amebic infections.

Blood Tests

Blood tests can be normal in meningitis but sometimes may show signs of infection, such as elevated white blood cells in a complete blood cell count (CBC) test or elevated proteins in a total protein test.

A procalcitonin blood test, which measures a substance that is often produced by cells at high levels during a bacterial infection, can help determine if a meningitis infection is more likely bacterial or viral. It can also be used to help diagnose sepsis.

Sepsis is an extreme response to an infection that causes the immune system to release chemicals into the bloodstream that damage your own tissues. If present with meningitis, a bacterial infection is usually to blame. (Viral meningitis does not typically involve the blood and is not associated with sepsis.)

A blood culture may be done if a bacterial infection is suspected. A sample of blood is examined for the growth of bacteria under a microscope.

Spinal Tap

A spinal tap is the only test that can confirm a diagnosis of meningitis.

You will either lie on your side with your legs bent toward your body in a fetal position or you will sit up with your upper body bent over slightly.

Your healthcare provider will sterilize an area of skin on your lower back and insert a hollow needle to allow CSF to be extracted. Your practitioner may measure the fluid pressure once your CSF starts to flow into the needle.

The fluid is sent to a laboratory for examination, where it is analyzed for proteins, white blood cells, blood, and infectious organisms. The results provide a great deal of information about a case of meningitis.

The most common side effect of a spinal tap is a headache, which typically lasts for a few hours. You can offset it by drinking fluids before and after the procedure and lying down for a few hours afterward.

Electroencephalogram (EEG)

An EEG is a test that measures the electrical activity of the brain. It is usually used to evaluate seizures and changes in consciousness.

While it is not common for meningitis to cause erratic electrical activity in the brain, you might need an EEG if you have either of these. Both are signs of severe meningitis that has advanced to encephalitis, an infection or inflammation of the brain.

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Imaging

The symptoms of meningitis may be similar to symptoms of other common disorders that affect the nervous system. Imaging can quickly help distinguish them.

Brain CT or MRI

Brain imaging using magnetic resonance imaging (MRI) or computed tomography (CT) can sometimes detect inflammation of meningitis. This is typically done along with a contrast, a substance that gets injected into a vein so tissues stand out more on scans.

While meningitis does not always produce the appearance of inflammation during brain imaging, these studies can also help identify other conditions—such as brain tumors, stroke, bleeding in the brain, abscesses, or encephalitis—that may present with similar symptoms.

Spine MRI

As with a brain MRI or brain CT, a spine MRI might detect inflammation of the meninges. It can also identify other problems such as tumors, bleeding, or abscesses. 

Chest X-Ray

A chest X-ray can identify an infection in the chest or lungs, which may be a sign that an infectious bacteria or virus is affecting other areas of the body besides the meninges.

Differential Diagnosis 

Some symptoms of meningitis—pain and fever, for example—overlap with those of other infections and conditions, particularly early on. As a healthcare provider works toward a diagnosis, they may look to rule out the following.

Flu or Viral Infection

Meningitis causes symptoms that are very similar to those of a routine viral infection.

The biggest difference is that meningitis symptoms more often involve the head, neck, and eyes. Other infections often involve the throat and sinuses and cause nausea, vomiting, and diarrhea.

Sometimes, however, meningitis is accompanied by the flu.

Migraine

Migraine headaches cause severe head and neck pain, nausea, and light-headedness, and may even produce neurological symptoms.

Systemic Infection

A severe infection affecting the body as a whole can produce symptoms similar to those of meningitis, including headaches and fevers.

The biggest difference is that systemic infection does not normally cause pain that changes with your body position the way that meningitis does.

Encephalitis

Encephalitis is inflammation or infection of the brain. It is more serious and life-threatening than meningitis and requires high-level care to prevent permanent neurological damage.

Encephalitis can cause behavioral changes, diminished consciousness, confusion, and/or seizures.

It is not common, but meningitis can progress to encephalitis, especially if you have an immune deficiency.

Muscle Strain

A strained/pulled muscle of the upper shoulders or upper back can cause severe pain that worsens with movement like meningitis.

The major difference between the two is that muscle strain pain is typically centered around a particular muscle and may worsen with its movement. The pain of meningitis tends to worsen primarily by changing the position of the head and neck.

Brain Abscess

A brain abscess is a type of infection in the brain that is localized to one area. Unlike meningitis, it is less likely to cause a fever.

A brain CT or MRI can identify a brain abscess, which requires treatment.

Low Blood Pressure

If you have low blood pressure for any reason, such as dehydration, blood loss, or a medical condition, you can experience dizziness, headaches, and fatigue.

As with meningitis, your symptoms can worsen with changes in body position.

If you have low blood pressure, you shouldn’t expect to have a fever or stiff neck. Your healthcare provider can measure your blood pressure with a quick, non-invasive test.

Seizures

Seizures often cause changes in consciousness and may be associated with lightheadedness, dizziness, and headaches.

When seizures cause fevers, they are generally very brief in duration and resolve on their own.

Occasionally, meningitis, and more commonly encephalitis, can cause seizures.

Stroke or Bleeding in the Brain, or Tumors

These conditions produce brain lesions that produce neurological symptoms. They can usually be detected with imaging tests.

In general, strokes, bleeds, and brain tumors produce specific neurological symptoms rather than generalized ones, but sometimes the symptoms can overlap with those of meningitis.

A neurological examination, which tests different functions of the brain, spinal cord, and nerves, plus brain imaging can determine your diagnosis.

Summary

Meningitis, an inflammation or infection of the meninges that line the brain and spinal cord, is most commonly caused by viral or bacterial infections. The hallmark symptoms are severe headaches, fever, and a stiff neck.

Meningitis is diagnosed via a spinal tap, which involves taking a sample of cerebrospinal fluid from the lower back to examine it. There are also often imaging and blood tests that can check for complications or other serious conditions with similar symptoms.