Kaan Meric, Ceren Yalniz, Hasan Gundogdu, Sibel Aydin, Zeynep Gamze Kilicoglu and Mehmet Masum Simsek
Introduction: Although MRI is the primary modality in the diagnosis of cranial metastasis, advanced MRI techniques such as spectroscopy, perfusion, diffusion weighted imaging, and diffusion tensor imaging are used to distinguish cranial metastasis from other pathologies. Since cranial metastasis are often highly vascular lesions, on perfusion examination they tend to exhibit elevated cerebral blood volume (rCBV). However since high-grade glial tumors also exhibit elevated rCBV, perfusion imaging cannot accurately differentiate between these two groups. Peritumoral rCBV values are actually more reliable in differential diagnosis of multicentric glial tutors and cranial metastasis.
Case report: A fifty-six-year-old male presented with progressive weakness in his left arm. MRI revealed multiple, different-sized lesions with a wide range of intensity changes. Some of the lesions displayed substantial peritumoral vasogenic edema. On DWI sequences, lesions demonstrated peripheral restricted diffusion. MRP sequences didn't show elevated rCBV values in T2-hyperintense peritumoral edema areas. The excisional biopsy of the lesion in left occipital lobe performed and the lesion's pathology result was reported as small-cell lung carcinoma metastasis, supporting our primary radiologic diagnosis.
Discussion: Advanced MRI techniques such as perfusion, spectroscopy, diffusion-weighted imaging (DWI) and diffusion tensor imaging (DTI) are used in the context of distinguishing cranial metastasis from high-grade glial tumors. Perfusion parameters like rCBV and rCBF are important to distinguish metastatic lesions from cranial lymphoma and benign cranial masses like abcess. However, since both cranial metastasis and high-grade glial lesions are both hypervacular, comparison of rCBV of the enhancing component of lesions cannot differentiate between these two groups. In such cases, rCBV values obtained from the peritumoral T2 hyperintense edema component of the lesion can help us. Conclusion: Multicentric glial tumors are on the differential diagnosis list of cranial metastasis. When conventional MRI techniques are insufficient to differentiate these two entities, perfusion values obtained from the peritumoral edema areas might be helpful.