Figure 1
T1W-TSE-COR
Coronal image at the level of popliteal fossa. Note the fusiform shape of the accessory split (arrowhead) of the lateral gastrocnemius (LG).
Accessory split of lateral head of gastrocnemius muscle
SectionMusculoskeletal system
Case TypeAnatomy and Functional Imaging
AuthorsStaikidou Ioanna, Mantzikopoulos Georgios, Pikoulas Konstantinos, Giannikouris Georgios, Kokkinis Konstantinos.
Connected authors
20 years, female
Clinical History
A 20 year-old female complained for knee pain and burning sensation of her left leg of a few weeks duration. The clinical examination was normal. An MRI examination of her left knee was requested for possible internal derangement of joint.
Imaging Findings
There is a fusiform mass-like structure located between the lateral head of gastrocnemius muscle and the vessels of the popliteal fossa (fig.1, 2, 3). Rostrally it has a thin attachment to the posterior cortex of the femur. The signal intensity of this structure follows that of muscle on all pulse sequences. Caudally it is fused with the lateral head of gastrocnemius muscle. The popliteal vessels are not compressed, coursing through the lateral head of gastrocnemius and this structure. The findings are suggestive of an accessory split of the lateral head of the gastrocnemius muscle.
There is a small amount of intraarticular fluid (fig.1a, 3) and a small amount of soft tissue oedema in front of the patella (fig.1b, 1c).
There is a small amount of intraarticular fluid (fig.1a, 3) and a small amount of soft tissue oedema in front of the patella (fig.1b, 1c).
Discussion
There are numerous accessory muscles in the human body. Most of them are asymptomatic and are discovered incidentally during imaging or surgery [1]. In some cases the discovery of these variations in musculature may explain patient’s symptoms and aid in diagnosis and treatment [1]. At the knee region there are variations of skeletal musculature that may provoke anomalous course of the popliteal vessels and may be responsible for symptoms of popliteal artery entrapment syndrome [2][fig.4]. An accessory muscle should be carefully evaluated, during imaging, as it may compress the neurovascular structures of the popliteal fossa and produce symptoms [3]. MR angiography will reveal the vascular compression [4]. The combination of plain MRI and MR angiography is needed to avoid unsuccessful and mainly unnecessary angioplasty procedures [4].
In our case the young woman had knee pain and intermittent claudication of the ipsilateral leg after physical activity. Symptoms subsided with rest and leg elevation. The MRI disclosed an accessory split of the lateral head of gastrocnemius muscle but the popliteal vessels were not compressed. The patient's symptoms could not be attributed to these findings, so conservative treatment and follow-up of the patient were suggested.
In our case the young woman had knee pain and intermittent claudication of the ipsilateral leg after physical activity. Symptoms subsided with rest and leg elevation. The MRI disclosed an accessory split of the lateral head of gastrocnemius muscle but the popliteal vessels were not compressed. The patient's symptoms could not be attributed to these findings, so conservative treatment and follow-up of the patient were suggested.
Differential Diagnosis List
Accessory split of lateral head of gastrocnemius muscle.
accessory muscle
tumour
Final Diagnosis
Accessory split of lateral head of gastrocnemius muscle.
References
[1] P. A. Sookur, A. M. Naraghi, R. R. Bleakney, R. Jalan, O. Chan, L. M. White (2008) Accessory muscles: anatomy, symptoms, and radiologic evaluation. RadioGraphics 28:481–499. (PMID: 18349452)
[2] T. A. Macedo, C. M. Johnson, J. W. Hallett, Jr., J.F. Breen (2003) Popliteal Artery Entrapment Syndrome: Role of Imaging in the Diagnosis. AJR 181:1259-1265. (PMID: 14573416)
[3] D. A. Elias, L. M. White, J. D. Rubenstein, M. Christakis, N. Merchant (2003) Clinical Evaluation and MR Imaging Features of Popliteal Artery Entrapment and Cystic Adventitial Disease. AJR 180:627–632 (PMID: 12591664)
[4] S. Atilla, E. T. Ilgıt, S. Akpek, C. Yucel, E. Turgut Talı, S. Isık (1998) MR imaging and MR angiography in popliteal artery entrapment syndrome. Eur. Radiol 8, 1025-1029 (PMID: 9683714)
Case information
| URL: | https://www.eurorad.org/case/12939 |
| DOI: | 10.1594/EURORAD/CASE.12939 |
| ISSN: | 1563-4086 |
License
This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.
Figure 2
T2W-TSE-SAG
Midsagittal level. Note the small attachment of the split (arrowhead) to the posterior femoral cortex. LG=lateral head of gastrocnemius.
Figure 3
PDW-TSE-FS-TRA
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Figure 4
Variations of gastrocnemius muscles
normal situation. Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Type I (5.6%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Type II (13.6%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Type III (37,5%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Type IV (9%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle, grey area=popliteus muscle, small grey area=fibrous band.
lateral accessory gastrocnemius split (9%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle, grey area=popliteus muscle, small grey area=fibrous band.
T1W-TSE-COR
Coronal image at the level of popliteal fossa. Note the fusiform shape of the accessory split (arrowhead) of the lateral gastrocnemius (LG).
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece.
T2W-TSE-SAG
Midsagittal level. Note the small attachment of the split (arrowhead) to the posterior femoral cortex. LG=lateral head of gastrocnemius.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece.
PDW-TSE-FS-TRA
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Sequential axial slices. Note the split (arrowheads) located between the lateral head of gastrocnemius muscle (LG) and the vessels of the popliteal fossa. It is fused caudally with the lateral gastrocnemius.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Variations of gastrocnemius muscles
normal situation. Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Type I (5.6%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Type II (13.6%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Type III (37,5%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Type IV (9%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle, grey area=popliteus muscle, small grey area=fibrous band.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
lateral accessory gastrocnemius split (9%). Red area=popliteal artery, blue area=popliteal vein, brown area=gastrocnemius muscle, grey area=popliteus muscle, small grey area=fibrous band.
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece
Staikidou I, Mantzikopoulos G, Pikoulas K, Giannikouris G, KAT Hospital, Athens, Greece