Combined HRCT and MRI in the Detection of CSF Rhinorrhea

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Abstract
Cerebrospinal fluid (CSF) rhinorrhea is a potentially dangerous problem. Accurate preoperative localization of the site of leakage is mandatory. The standard diagnostic technique is computed tomography (CT) cisternography. Because of its related risks, however, various alternatives have been suggested. High-resolution CT (HRCT) provides good bony details, but fluid is poorly detected. In contrast, T2-weighted magnetic resonance imaging (MRI) shows CSF as a bright signal, but spatial resolution is poor as is the depiction of bony details. To overcome the shortcomings of both techniques, we superimposed the images obtained from each modality and used the result to plan surgical explorations. The sensitivity of HRCT was 88.25%. Fat-suppressed T2-weighted MRI detected a CSF-like density in 18 cases (90%) with a sensitivity of 88.88%. Superimposing the CTs and MRIs accurately localized the site of CSF leakage in 17 of 19 cases with a sensitivity of 89.74%. This finding compares favorably with the results of other techniques. We thus recommend this technique as the primary diagnostic method of choice for the investigation of patients with CSF rhinorrhea. Drs. Mostafa and Khafagi have reviewed their experience with the detection of cerebrospinal fluid (CSF) rhinorrhea and have suggested that fusing high-resolution coronal computed tomography (CT) images of the base of the skull with highly fat-suppressed T2-weighted magnetic resonance imaging (MRI) sequences might offer the best of both worlds, marrying high spatial resolution with the ability to visualize the continuity of CSF. Their success in 17 of 19 patients is impressive. One has to remember that the gold standard of CT Omnipaque studies is not particularly comfortable for patients, and the false-negative rate is appreciable. However, one must be cautious about performing CT and MRI in close temporal proximity. Furthermore, the angulation of the cuts must be similar to maximize accuracy of the fusion. I suspect, however, that in a larger series a certain degree of inaccuracy and misleading changes in the paranasal sinuses would still be encountered. In such cases, one could always refer to an intrathecal CT study. In summary, this article is a valuable addition to the literature. I intend to try this technique at my institution to see if we can replicate these encouraging results.

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