MRI plays an important role in diagnosing intracranial infections. MRI study may show many abnormalities, including a variable degree of abnormal meningeal contrast enhancement. The standard contrast-enhanced magnetic resonance series at most institutions is CE-T1WI. On T1WI, however, meningeal enhancement is sometimes unnoticeable [5].
In detection of inflamed meninges, the CE-FLAIR sequence is superior to CE-T1WI. The meningeal disease can be visualized more effectively with CE-FLAIR images than it is in CE-T1WI because CE-FLAIR is more sensitive to lower contrast concentration as a result of its marked sensitivity to limited alteration of CSF composition [6, 7].
CE-FLAIR images also allow for more accurate differentiation between abnormal meningeal enhancement and the cortical veins [1]. CE-FLAIR demonstrates no enhancement of the cortical veins or normal meninges that can cause confusion with pathologically enhancing meninges on CE-T1WI.
In the current study, the sensitivity of the CE-FLAIR sequences was 91.9%, the specificity 100%, the positive predictive value 100%, and the negative predictive value 72.7%. The results of the current study are in accordance with Mubasher [4], who stated that CE-FLAIR images had a sensitivity of 95.3% and CE-T1WI a sensitivity of 76.7%, as well as Azad et al. [8], who noted that the CE-FLAIR images showed improved sensitivity, diagnostic accuracy, and better correlation with CSF compared to CE-T1WI sequences. Researchers concluded that the CE-FLAIR series is an appropriate modality to determine meningitis and could be included in the routine MR procedure.
In this study, the results of CE-FLAIR were compared to the results of CE-T1WI in confirming the diagnosis of meningitis and the final diagnosis was based on CSF results. No false positive outcomes were found in both CE-FLAIR and CE-T1WI. These results are approximately similar to Allesandra et al. [9], who studied the accuracy of MRI in early diagnosis of infectious meningitis with a focus on the importance of the series of contrast-enhanced FLAIR. There was confirmation of infectious meningitis in 12 patients. In all 12 patients, MRI CE-FLAIR showed abnormal meningeal enhancement, whereas CE-T1-WI was only positive in six cases. No false-positive or false-negative outcomes were found in CE-FLAIR sequences in their study. They concluded that if the CE-FLAIR sequence is used, MRI may play a crucial role in early screening for infectious meningitis.
In the current study, the CE-T1WI was routinely done without fat saturation. This may explain the difference in results compared to research done by Galassia et al. [10], who found that pathological meningeal enhancement was seen in 35 patients in CE-T1WI with fat saturation and in 33 patients with CE-FLAIR. They found that, for the depiction of intracranial meningeal diseases, CE-T1WI with fat saturation is superior to CE-FLAIR sequence.
This study showed that CE-FLAIR has higher sensitivity yet equal specificity compared to CE-T1WI. This is in contrary to a study done in 2006, by Parmar and his colleagues [11] who published a study to evaluate CE-FLAIR in the assessment of meningitis and proposed that CE-FLAIR has equal sensitivity but a higher specificity compared to CE-T1WI for diagnosing leptomeningeal enhancement.
Falzone et al. [12] conducted a study on CE-FLAIR versus CE-T1WI in brain imaging. They concluded the dominance of CE-FLAIR images compared to CE-T1WI in the identification of brain lesions. The findings of our analysis are comparable to their results, yet it is not possible to make an exact comparison as their study included other brain parenchymal lesions other than meningitis.
Although this study was focused on detecting pathological meningeal enhancement due to the inflammatory process, CE-FLAIR may be of value in detecting other causes of meningeal enhancement.
One study by Ercan et al. [13] reported that CE-FLAIR imaging is a valuable adjunct to CE-T1WI. Pre-contrast and contrast-enhanced FLAIR accurately detect leptomeningeal, cisternal, and cranial-nerve metastases [13]. Ultimately, due to its high sensitivity and specificity, the findings of our study promote the use of CE-FLAIR sequence to confirm the diagnosis of meningitis.