Expanding on MRI characteristics of neuromuscular choristoma: a single center retrospective review.

Objective: Neuromuscular choristoma (NMC) is a rare condition affecting peripheral nerves, most commonly the proximal sciatic nerve. It is characterized by the presence of muscle tissue within the nerve. Patients typically present with neuropathic symptoms. NMC is associated with the development of NMC-associated desmoid-type fibromatosis (NMC-DTF). In this study, we report findings of qualitative and quantitative MRI signal intensities to further expand on known MRI imaging features of NMC.

Methods and materials: Retrospective analysis of NMC cases of the sciatic nerve from our institution was conducted. The sciatic nerve was selected as a model example due to its common involvement. Inclusion criteria were a confirmed NMC diagnosis and available MR exams. MRI signal intensities from the affected nerves and normal contralateral nerves were compared, normalized to muscle signal intensity for consistency across different MRI sequences.

Results: Fourteen patients (8 men, 6 women) met the inclusion criteria. No significant differences in T1 or T2 signal intensities were found between NMC and unaffected nerves. However, NMC demonstrated significantly higher post-contrast signal intensities (p = 0.003) compared to unaffected nerves. These findings were consistent across the proximal and distal segments of the affected nerve.

Conclusion: Our study expands the understanding of MRI features in NMC. The increased post-contrast enhancement in NMC may serve as a useful diagnostic tool and could potentially play a role in detecting areas at risk for future DTF development. This highlights the importance of comprehensive imaging, including post-contrast sequences and ideally imaging of the entire course of the affected nerve.