Preliminary Diagnosis: Meningitis
I. What imaging technique is first-line for this diagnosis
- MR imaging of the brain and spine with and without contrast
II. Describe the advantages and disadvantages of this technique for diagnosis of meningitis.
Advantages
- May be diagnostic in certain clinical settings
- Able to locate the focal area of meningeal inflammation and predict any neurologic abnormalities
- Able to evaluate for any secondary complications from a primary infectious or inflammatory meningitis, such as an intraaxial or extraaxial abscesses, empyema, encephalitis, ventriculitis, hydrocephalus, and/or petechial hemorrhages
- Does not make use of any ionizing radiation
Disadvantages
- Expensive
- Time-consuming
- Requires marked patient cooperation to limit motion artifact
- MR imaging with intravenous contrast requires that patient have good renal function with GFR >60; administration of intravenous contrast decided on a case by case basis with GFR >30 and <60
- Meningitis is a clinical/laboratory diagnosis that may occur in the setting of normal imaging
III. What are the contraindications for the first-line imaging technique?
- Contraindicated in patients with non-MR compatible hardware and foreign bodies
- Intravenous contrast requires that patient have good renal function with GFR >60. Administration of intravenous contrast is decided on a case by case basis with GFR >30 and <60.
IV. What alternative imaging techniques are available?
- Nonenhanced and enhanced CT imaging of the brain
- CT spinal myelography
V. Describe the advantages and disadvantages of the alternative techniques for diagnosis of meningitis.
Nonenhanced and enhanced CT imaging of the brain
Advantages
- Able to detect primary forms of infection causing a secondary meningitis, such as paranasal sinus and/or temporal bone infection
- May be performed much quicker than MR imaging, requires less patient cooperation, and is associated with less motion artifact compared to MR imaging
Disadvantages
- Less specific and less adept in detailing secondary complications from a primary meningitis.
- Exposes the patient to ionizing radiation
- Has less soft tissue detail compared to MR imaging
CT spinal myelography
Advantages
- Demonstrates thickening of the nerve roots, blockage of CSF flow, and irregular contour of the cauda equina/thecal sac to demonstrate/diagnose spinal meningitis
Disadvantages
- Invasive procedure that exposes a patient to all the risks of an invasive procedure
- Exposes a patient to ionizing radiation
- May not be helpful in diagnosing intracranial compared to spinal meningitis
VI. What are the contraindications for the alternative imaging techniques?
Nonenhanced and enhanced CT imaging of the brain
- Contraindicated in pregnant patients, especially within the first two trimesters
CT spinal myelography
- Contraindicated in hypocoagulable patients: INR greater than 2.0 and platelets less than 50,000
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