How Meningitis Is Diagnosed

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

The diagnosis is made using a lumbar puncture (LP), which is an invasive but largely safe, diagnostic test that involves removing spinal fluid using a needle placed into the lower back.

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Self-Checks/At-Home Testing 

Headaches accompanied by a stiff neck are the hallmark characteristics of meningitis, and there are several other important signs that you can look out for if you think that you or your child may have meningitis, including a painful neck, fevers, back pain, a rash anywhere on the body, and flu-like symptoms.

Meningitis Symptoms

  • Headache
  • Stiff neck
  • Fever
  • Back pain
  • Rash
  • Flu-like symptoms

Labs and Tests

Several tests and diagnostic procedures can confirm the diagnosis of meningitis. When meningitis is caused by an infection, CSF samples may be used to identify the specific infection that's causing it.

Funduscopic Exam

Your doctor may look inside your eyes using an ophthalmoscope, which magnifies the view of your eye without directly touching it. This non-invasive test allows your doctor to see whether you have swelling of the optic nerves or any other evidence of inflammation or increased pressure in your eyes—which is a sign that's sometimes indicative of a severe case of meningitis.

Ear Exam

During an ear examination, your doctor will look in your ear canal. This examination can show swelling, fluid, redness, or other signs of an underlying ear infection accompanying meningitis (more common in children). If there is fluid draining, it may be sampled and sent to a laboratory for testing to identify infectious organisms.

Blood Tests

Blood tests can be normal in meningitis but sometimes may show signs of infection, such as elevated white blood cells. If your meningitis is complicated with sepsis (infection of the blood), your blood culture may show the type of bacteria causing the infection as well. Viral meningitis does not typically involve the blood and is not associated with sepsis.

Lumbar Puncture (LP)

An LP—also called a spinal tap, is a procedure that involves the extraction of CSF from your body. This is, for the most part, a safe test, performed by a doctor.

The fluid is sent to a laboratory for examination, and the results provide a great deal of information in the diagnosis of meningitis. CSF can be analyzed for proteins, white blood cells, blood, and infectious organisms.

How a Lumbar Puncture Is Done

If you have an LP, you will either lie on your side with your legs bent towards your body in a fetal position or you will sit up with your upper body bent over slightly. Your doctor will sterilize an area of skin on your lower back and will insert a hollow needle to allow the fluid to flow into it. Your doctor may measure the fluid pressure once your CSF starts to flow.

The most common side effect of an LP 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 after the procedure.

Electroencephalogram (EEG)

An EEG is an electrical test that can measure 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 seizure activity or changes in consciousness, which are signs of severe meningitis that has advanced to encephalitis (infection of the brain).

Meningitis Doctor Discussion Guide

Get our printable guide for your next doctor's appointment to help you ask the right questions.

Doctor Discussion Guide Man

Imaging

Imaging studies can be helpful in the evaluation of meningitis. The symptoms of meningitis may be similar to symptoms of other common neurological disorders, so imaging can quickly distinguish neurological conditions from each other. 

Brain CT or MRI

Brain imaging with contrast injection can sometimes detect inflammation of meningitis. While meningitis does not always produce the appearance of inflammation on brain imaging studies, these studies can also identify other neurological conditions that may present with similar symptoms to those of meningitis—such as brain tumors, stroke, bleeding in the brain, abscesses, or encephalitis.

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.

Differential Diagnosis 

Because meningitis can cause pain and fevers, it may overlap in symptoms with other infections and neurological conditions, particularly early on.

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, while other infections often involve the throat and sinuses and cause nausea, vomiting, and diarrhea. Sometimes, however, meningitis is accompanied by the flu.

Migraine Headache

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

If you have not had migraine headaches before, you should never assume that your head or neck pain is a migraine. If you have had migraine headaches, you should seek medical attention if your pain is different than usual or is accompanied by a fever.

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.

If you have symptoms of meningitis, you should seek medical attention promptly. Your doctor’s examination and diagnostic tests can differentiate between the two conditions.

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

Muscle Strain

A strained or pulled muscle of the upper shoulders or upper back can cause severe pain that also worsens with movement. The major difference between a muscle strain and meningitis is that the pain of a muscle strain is typically centered around a particular muscle and is more likely to become worse with moving the area near the center of pain, while the pain of meningitis is exacerbated primarily by changing the position of the head and neck.

Brain Abscess

A brain abscess is a type of localized area of infection in the brain. Unlike meningitis, it may cause localized rather than generalized neurological symptoms and 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, and your doctor 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, the fevers 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 and that can usually be detected with imaging tests. In general, strokes, bleeds, and brain tumors produce specific neurological symptoms rather than generalized symptoms, but sometimes the symptoms can overlap with those of meningitis. A neurological examination and brain imaging can determine your diagnosis.

Frequently Asked Questions

How do you diagnose meningitis?

A lumbar puncture is the primary tool for diagnosis. By analyzing a sample of cerebrospinal fluid (CSF), the lab can sometimes definitively diagnose meningitis based on CSF glucose (sugar), white blood cells, and protein levels. The analysis can also determine the type of meningitis, which can be viral, bacterial, fungal, or aseptic (unrelated to infection).

What are the signs and symptoms of meningitis?

Characteristic signs include severe headache, high fever, stiff neck, difficulty concentrating, confusion, sleepiness, nausea, vomiting, and light sensitivity. During a meningococcal outbreak, doctors will usually start treatment in symptomatic people even before an official diagnosis is reached, since meningococcal meningitis is serious.

How do blood tests help diagnose meningitis?

Usually, the complete blood count (CBC) is normal in meningitis, but sometimes this test may detect white blood cell count (WBC) changes that could accompany meningitis. Sometimes a high WBC count with a C-reactive protein (CRP) test can help differentiate bacterial meningitis from aseptic meningitis. A procalcitonin blood test can sometimes help differentiate between viral and bacterial meningitis.

How is an eye exam used to diagnosed meningitis?

An eye exam cannot diagnose meningitis, but it may show signs of the disease. Using an ophthalmoscope, the doctor can see if there is any swelling of the optic nerve, which can occur in meningitis due to increased cerebrospinal fluid pressure.

What role do imaging tests play in diagnosing meningitis?

Imaging tests like an MRI or CT scan serve several important functions:

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