This study suggests that diffusion-weighted imaging can effectively distinguish nonthrombosed distensible venous malformations (DVMs) of the orbit from other orbital tumors.

Study design

The authors performed a retrospective case-control study of patients with nonthrombosed orbital DVMs and patients with other histologically confirmed orbital tumors. The main outcome measure was the apparent MRI diffusion coefficient of these lesions.

Outcomes

Of the 9 cases of nonthrombosed DVM, 3 were initially misdiagnosed as solid orbital tumors. The mean apparent diffusion coefficient of DVMs was 2.8 × 10³ mm²/s. By contrast, the mean apparent diffusion coefficient of other histologically confirmed tumors was 1.18 × 10³ mm²/s (P<0.001).

Limitations

The study is primarily limited by its small sample size. A larger sample may have revealed solid tumors with diffusivities that fall within the range of nonthrombosed orbital DVMs (2.42–3.94 × 10³ mm²/s). It should also be noted that magnetic fields and eddy currents at the interface between bone and soft tissue are particularly pronounced within the orbit. For this reason, imaging artifacts may be severe within the orbit, making it difficult to evaluate the apparent diffusion coefficient map.

Clinical significance

Certain nonthrombosed DVMs can evade diagnostic suspicion and mimic solid orbital tumors on standard MRI sequences. In this single-institution series, diffusion-weighted imaging effectively distinguished these nonthrombosed DVMs from other orbital tumors.