How Meningitis Is Diagnosed

meningitis diagnosis
© Verywell, 2018 

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

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

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 headaches, stiff or painful neck, fevers, back pain, a rash anywhere on the body, and flu-like symptoms.

Labs and Tests

Several tests can confirm the diagnosis of meningitis. When meningitis is caused by an infection, tests may be able to identify the specific virus or bacteria 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 or cloudiness behind your eye, both of which can indicate advanced meningitis that requires urgent medical care.

Ear Exam

If you have meningitis that has caused a substantial amount of swelling in or around the brain, your doctor may see signs of swelling by looking inside your ear.

Blood Tests

Blood tests may show signs of infection such as elevated white blood cells. If your meningitis is complicated with sepsis (infection of the blood), your blood tests may show the bacteria as well. Viral meningitis does not typically involve the blood and is not associated with sepsis.

Lumbar Puncture (LP)

A test that involves removal of cerebrospinal fluid (CSF) from your body, an LP is an invasive test. This is a safe test, and a doctor who has experience with it performs the procedure. CSF is the fluid that surrounds your brain and spinal cord and it provides the most diagnostic information. It'll tell whether you have meningitis and exactly what type. CSF can be analyzed for proteins, white blood cells, blood, and infectious organisms.

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 and lying down in a flat position for a few hours.

Electrencephalogram (EEG)

An EEG is an electrical test that can detect 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).

Imaging

Imaging studies can be especially helpful in the evaluation of meningitis. The symptoms of meningitis may be difficult to differentiate from 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 detect inflammation of meningitis. While inflammation of the meninges does not always appear on brain imaging studies, these studies can also identify other neurological conditions such as brain tumors, stroke, bleeding in the brain and abscesses, and encephalitis that may present with similar symptoms to those of meningitis.

Spine MRI

As with a brain MRI or brain CT, a spine MRI might be able to detect inflammation of the brain. It can also identify other problems such as tumors, bleeding. or abscesses. While brain CT is helpful, spine CT is usually not the recommended test for imaging the spine.

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 on 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. Often, 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 itself. It is considered more serious and life-threatening than meningitis and requires high-level care to prevent permanent neurological damage.

The biggest difference between the two conditions is the severity. If you have symptoms of meningitis, you should seek medical attention promptly and 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 differences 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 nearby the center of pain, while pain of meningitis is exacerbated primarily by movements of the head and neck.

Brain Abscess

A brain abscess is an area of infection in the brain. Unlike meningitis and encephalitis infections, it may cause specific 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 detect low blood pressure with a simple blood pressure check. 

Seizures

Seizures often cause changes in consciousness and may be associated with lightheartedness, 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 what are described as lesions in the brain, which produce neurological symptoms. In general, strokes, bleeds, and brain tumors produce specific neurological symptoms rather than generalized symptoms, but sometimes the symptoms of these conditions can overlap with those of meningitis. A neurological examination and brain imaging can determine your diagnosis when symptoms overlap.

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