Clinicoradiologic Differences between Orbital Schwannoma and Cavernous Venous Malformation: A Retrospective Comparative Case Series

OBJECTIVE To compare the clinical and radiological characteristics, and surgical outcomes of orbital schwannoma and cavernous venous malformation (CVM). MATERIALS AND METHODS We retrospectively compared 13 and 26 patients with biopsy-proven orbital schwannoma and CVM, respectively, analyzing clinical features, magnetic resonance imaging (MRI) and computed tomography (CT) features (including dynamic contrast enhancement [DCE] imaging, apparent diffusion coefficient [ADC] and CT values), surgery type, and outcomes. RESULTS In both the schwannoma (mean age, 45 ± 16.7 years; 53.8% females) and CVM (mean age, 50.2 ± 8.6 years; 61.5% females) groups, gradual proptosis was the most common symptom (53,8% and 46.2%; mean measurements of 3.0 ± 1.97 mm and 2.5 ± 1.64 mm, respectively. Both groups had a common intraconal location (61.5 and 53.8%; mean sizes of 21.0 ± 7 mm and 20 ± 5 mm, respectively). On MRI, schwannomas were significantly more heterogeneous than CVM (p = 0.044). Tail sign and target sign were seen in 46.2% of schwannomas (p < 0.001), and linear T2 hypointensity was present in 57.7% of CVM (p = 0.008). DCE-MRI revealed diffuse early enhancement for schwannomas and nodular early enhancement for CVMs (p < 0.001). Schwannomas displayed higher ADC value without statistical significance (1.64 ± 0.56 x 10 ^− 3 mm ² /s vs. 1.26 ± 0.21 x 10 ^− 3 mm ² /s; p = 0.078), but significantly lower median CT value (40 HU vs. 56 HU; p = 0.001) than CVM. Majority underwent en bloc surgical excision without capsule violation (schwannoma, 76.9%; CVM, 100%). Schwannoma patients more frequently required lateral bony marginotomy compared to CVMs (23.1% vs. 7.7%). 23.1% of schwannoma patients underwent subtotal resection to avoid complications, with no recurrence observed during a 4.3 ± 3.4-year follow-up. CONCLUSION MRI aids in pre-operatively diagnosing orbital schwannoma and CVM. Schwannomas exhibit heterogeneous T2WI appearance, diffuse early-phase enhancement, and tail/target signs. Conversely, CVMs display homogenous T2WI signal, linear T2 hypointensity, and nodular early-phase enhancement. Additionally, schwannomas showed lower value on CT. For schwannomas, physicians should not risk vision loss or strabismus for total excision in anatomically challenging cases, as the risk of recurrence after subtotal resection is rare.