What does gracilis myopathy look like on CT and MRI?

Vet Comp Orthop Trauma 2024

December 17, 2024

Hana Gunovska, Cesar Llanos, Ella Fitzgerald, Emili Alcoverro, Katharina Flatz, Cesar Gomes, Sergio A. Gomes

Background
Gracilis myopathy, also known as fibrotic myopathy, is a condition characterized by a distinctive weight-bearing gait abnormality. It primarily affects the gracilis–semitendinosus muscle complex in dogs, especially German Shepherds. Advanced imaging, such as computed tomography (CT) and magnetic resonance imaging (MRI), can provide detailed insights into the affected musculature, which is critical for diagnosis and management.

Methods
This retrospective, multicenter study reviewed the medical records of dogs with gracilis myopathy, confirmed through characteristic gait and advanced imaging (CT or MRI). Seven cases were included, and imaging protocols varied across four veterinary institutions. Imaging features were analyzed using predefined criteria to document muscle changes, including fibrotic bands and anatomical abnormalities.

Results
All seven dogs were German Shepherds with an average age of 69.6 months. Imaging findings revealed:
MRI: Hypointense fibrotic bands (T1, T2, PDW) along the gracilis muscle, muscle shortening, and signal abnormalities at the symphyseal tendon. Enhanced contrast was noted at the muscle origin.
CT: Hyperattenuating fibrotic bands and tendon thickening. Muscle atrophy was evident in most cases. Six cases were managed conservatively, while one underwent surgical excision of the gracilis muscle.


Limitations
The small sample size and retrospective, multicenter design resulted in varied imaging protocols. Only a subset of cases had comprehensive follow-up, limiting long-term outcome analysis.

Conclusions
CT and MRI are valuable tools for diagnosing gracilis myopathy, offering detailed visualization of affected muscle structures. MRI is preferred for its superior soft tissue resolution. Further studies with larger samples are needed to evaluate treatment outcomes and refine diagnostic protocols.

Fig 2. Case 4. (A) CT soft tissue post-contrast (arterial): bilateral hyperattenuating fibrous bands in the medial aspect of the gracilis muscles
(arrow). The left gracilis is decreased in volume. Additionally, there is moderate left-sided disuse muscle atrophy. (B) CT soft tissue postcontrast (arterial): thickening and increased attenuation at the origin of the left gracilis. Case 5: (C) CT soft tissue pre-contrast: right
hyperattenuating fibrous band in the gracilis muscle. The gracilis muscle is slightly rounded in shape. (D) CT soft tissue pre-contrast: similar
changes in the left limb (arrow). Mild muscle atrophy. (E) Image 2: CT soft tissue pre-contrast. Hyperattenuating region at the origin of the left
gracilis muscle (arrow). Case 6: (F) CT soft tissue pre-contrast: hyperattenuating fibrous band in the medial aspect of the gracilis (arrow).
Ipsilateral muscle atrophy. (G) Close-up from (F). Case 7: (H) CT pre- and post-contrast soft tissue. Contrast enhancement at the origin
of the right gracilis muscle (arrow). (I) Hyperattenuating band in the medial aspect of the right gracilis muscle (arrow). Otherwise normal in
size/shape, without significant muscle atrophy. (J) Close-up from (I). CT, computed tomography

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