What is the role of CT scanning in the workup of Haemophilus influenzae type b (Hib) meningitis?

Updated: Jul 09, 2018
  • Author: Prateek Lohia, MD, MHA; Chief Editor: Niranjan N Singh, MBBS, MD, DM, FAHS, FAANEM  more...
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Either CT or MRI may provide information concerning the usual space-occupying lesions or other complications that may result from Hib meningitis and either modality provides information concerning some alternative diagnoses. Generally, CT is obtained because it is usually more readily available and requires less time. Patients must be monitored by qualified personnel during imaging because seizures or critical elevation in ICP may develop while the study is being performed.

The most common imaging findings in cases of Hib meningitis at or shortly after presentation are meningeal, ependymal, or choroidal enhancement due to meningitic inflammation. Inflammatory exudate may be demonstrable in the basilar cisterns, especially the foramen magnum. The accumulation of inflammatory exudate tends to widen the basilar cisterns and the cortical sulci (particularly over the convexities of the forebrain hemispheres).

Findings on CT scanning may be fully normal in the acute stage of Hib meningitis. MRI scanning, if performed, may reveal the abnormalities noted above with even greater sensitivity and definition than CT scanning.

Abnormalities indicative of meningitic inflammation and exudate support the diagnosis of meningitis but are not very specific with regard to organism and usually do not modify therapy or prognosis. Thus, for example, the extent of meningeal enhancement is not indicative of prognosis. Rarely, adults may present with Hib meningoventriculitis, evident as ventricular debris, periventricular hyperintense signal, and periventricular ependymal enhancement. [21]

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