Meningitis is suspected based on medical history and physical exam. To confirm the diagnosis, the doctor will admit the patient and do certain diagnostic tests such as CT scan or MRI scan of the brain, CSF test and blood test.
History and examination: During the exam, your doctor may ask questions such as:
The doctor will do general examination and assess your blood pressure, peripheral pulses, skin for rash etc. During examination, the doctor will examine your nervous system function as well such as your reflexes, muscle strength, stiffness of neck or any other abnormal neurological problems.
Blood cultures: In this test, sample of blood is taken in a sterile manner from a vein and is sent to a laboratory for testing. The sample is placed in a special dish to see if it grows microorganisms, particularly bacteria. Blood sample may be analysed after making a slide to which stains are added (Gram's stain) under microscope for bacteria, fungus.
Brain CT or MRI Scan: Computed tomography scan (CT scan) and magnetic resonance imaging scan (MRI scan) are painless and non-invasive tests that are usually done if meningitis or any other pathology in the brain is suspected. These tests take a series of detailed pictures of part of the body that is being examined. During brain CT scan, series of images of the brain are taken. These pictures provide details of the brain and surrounding tissue. The images can show any abnormality such as swelling or inflammation of the brain or meninges in meningitis or other abnormalities such as brain tumour, size of the ventricles, brain edema (swelling of brain tissue) etc. If needed, your doctor will take CT and MRI pictures after injecting a dye (Iodine or Gadolinium contrast dyes) intravenously. The images obtained after injecting the contrast dye give better details of the brain and other structures inside the cranium (skull bone). An MRI scan gives better information as compared with CT scan i.e. it can detect abnormalities that are very small in size and may not be seen on a CT scan.
Spinal fluid analysis: Analysis of cerebrospinal fluid (CSF) is a definitive test to diagnose meningitis. It is often done if meningitis is suspected. The cerebrospinal fluid is the fluid present around the brain and spinal cord that helps to protect your brain and spinal cord. The fluid is removed under local anaesthesia from the lower spine using a long, thin needle. It is examined for white blood cell count, sugar content and protein. In meningitis, the CSF fluid composition is altered and it often shows a low sugar (glucose) level along with an increased white blood cell count and increased protein. The exact bacterium that's causing the illness can be isolated from CSF fluid during testing.