The Importance of Imaging to Guide Treatment: Intramuscular Psoas Mass with Lumbosacral Plexopathy.

Sir,

Imaging is an important part of a patient's workup. It is imperative that the provider, specifically an interventional pain physician or orthopedic spine surgeon, be able to not only obtain a thorough history and complete a focused physical examination but then use the information obtained to know what specific imaging to order. In addition, the provider must be able to review the imaging themselves so as not to rely only on the radiologist's final read and ultimately use those results to correlate future treatment moving forward.

As a specific example, we encountered a specific patient who presented right lower extremity pain and paresthesias localized over the anterior and lateral aspect of thigh, loss of sensation in the anterior and lateral thigh, and a radiculopathy of the L3/L4 distribution consistent with the distribution of the femoral nerve. Given this information obtained from the patient's history and physical examination, initially, a lumbar posteroanterior (PA) radiograph was ordered, followed by a lumbar magnetic resonance imaging (MRI) with and without contrast with the goal that these specific imaging modalities would provide us with additional corollary information to guide subsequent treatment.

Lumbar PA radiograph [Figure 1a] revealed normal vertebrae bone findings, but careful review revealed asymmetry in the para-spinal psoas muscle. Lumbar MRI characterized a heterogeneous intramuscular mass [Figure 1b] within the psoas. The mass measured 12 cm in length and 6 cm in diameter at its largest section. It enhanced with gadolinium contrast on T1 sequences [Figure 1c and d]. It expanded the periphery of the psoas muscle and compressed the L2, L3, and L4 nerve roots.

Figure 1

(a) Lumbar posteroanterior radiograph revealed a prominence of the right psoas muscle as compared to the left. (b) Lumbar magnetic resonance imaging characterized a heterogeneous intramuscular mass within the psoas. (c and d) Psoas mass enhanced with gadolinium contrast on T1 sequences

The differential diagnosis included schwannoma, possibly with malignant degeneration, intramuscular myxoma, and myxofibrosarcoma. At this point, in order to trim the differential down to a specific diagnosis, it was decided that an image guided procedure, specifically a computed tomography (CT)-guided biopsy, was ordered and subsequently performed. The CT-guided biopsy revealed a benign nerve sheath tumor most consistent with schwannoma. A schwannoma is a common benign soft-tissue tumor. It is well encapsulated and does not adhere to the surrounding tissue, often presenting as a delayed diagnosis due to their slow and insidious growth, but large lesions present more aggressively with local compression, adherence, and bone rearrangement.[123] Schwannoma demonstrates certain radiological features including a well-circumscribed mass with heterogeneous contrast enhancement, calcifications, and cystic portions.[3]

MRI is the imaging modality for preoperative diagnosis demonstrating hypointensity in T1-weighted images and hyperintensity in T2-weighted images. During fat suppression sequence, the schwannoma maintains its hyperintensity.[3] Although radiologists are the imaging specialists in the medical community, it is important that providers be cognizant of what imaging to order in order to guide and further correlate future therapy and treatment toward their patient in the process of a detailed and thorough workup.

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Conflicts of interest

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