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Table of Contents    
Year : 2013  |  Volume : 61  |  Issue : 6  |  Page : 668-669

Sciatica caused by pyomyositis of the piriformis muscle

1 Department of Orthopedic Surgery, Chiba Aoba Municipal Hospital; Chiba University Graduate School of Medicine, Chiba, Japan
2 Department of Orthopedic Surgery, Chiba Aoba Municipal Hospital, Chiba, Japan
3 Department of Orthopedic Surgery, Toho University Sakura Medical Center, Sakura, Japan
4 Department of Orthopedic Surgery, Chiba University Graduate School of Medicine, Chiba, Japan
5 Department of Orthopedic Surgery, University of Tsukuba, Tsukuba, Japan

Date of Submission30-Oct-2013
Date of Decision30-Oct-2013
Date of Acceptance05-Dec-2013
Date of Web Publication20-Jan-2014

Correspondence Address:
s Masao Koda
Department of Orthopedic Surgery, Chiba Aoba Municipal Hospital; Chiba University Graduate School of Medicine, Chiba
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.125291

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How to cite this article:
Koda M, Mannoji C, Watanabe H, Nakajima A, Yamada T, Rokkaku T, Murakami KI, Murakami M, Ikeda O, Yamazaki M, Furuya T. Sciatica caused by pyomyositis of the piriformis muscle. Neurol India 2013;61:668-9

How to cite this URL:
Koda M, Mannoji C, Watanabe H, Nakajima A, Yamada T, Rokkaku T, Murakami KI, Murakami M, Ikeda O, Yamazaki M, Furuya T. Sciatica caused by pyomyositis of the piriformis muscle. Neurol India [serial online] 2013 [cited 2023 Dec 8];61:668-9. Available from:


The piriformis muscle has endopelvic origin, exits the pelvis through the greater sciatic notch and inserts into the piriformis fossa on the greater trochanter of the femur. Since the sciatic nerve also leaves the pelvis through the greater sciatic notch, any pathology of the piriformis muscle could result in the entrapment to the sciatic nerve, the piriformis syndrome. [1] Pyomyositis of the piriformis muscle can produce swelling of the muscle, resulting in compression of the sciatic nerve, thus can present with piriformis syndrome. [2],[3] We report a rare case of pyomyositis of piriformis muscle presenting as sciatica.

A 42-year-old female nurse presented with severe right-sided sciatica. The pain worsened limiting her ambulation. With a diagnostic possibility of lumbar disc herniation, she was referred to our facility. On admission, the body temperature was 38.4°C. Due to severe sciatica, she was unable to ambulate. Freiberg test could not be performed because of severe pain. Laboratory evaluation revealed elevated white blood cell count (12, 500/mm 3 ) and C-reactive protein level (13.9 mg/dl). Magnetic resonance imaging (MRI) of lumbar spine performed at the other facility showed no obvious abnormality. MRI of the pelvis revealed high intensity change and swelling of piriformis muscle in T2-weighted image [Figure 1]a. Contrast enhanced computed tomography (CT) also showed swelling of piriformis muscle and rim-enhanced low density mass lesion within piriformis muscle [Figure 1]b. The diagnosis of piriformis syndrome secondary to pyomyositis of piriformis muscle was considered.
Figure 1: Pre - and post - operative magnetic resonance imaging (MRI) and computed tomography (CT). Pre - operative T2 - weighted axial MRI (a) and enhanced CT (b) at the greater sciatic notch show muscle swelling (arrowheads) of right side piriformis muscle. MRI shows intramuscular T2 high lesion (a, arrow) and enhanced CT shows intramuscular rim-enhancement (b, arrow), both suggesting abscess formation in piriformis muscle. Post - operative T2 - weighted axial MRI (c) and plain CT at the greater sciatic notch show no abscess in the piriformis muscle (d)

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In spite of intravenous antibiotic, the pain worsened. Under general anesthesia, in the lateral decubitus position, a skin incision from just posterior to the greater trochanter to the middle of the buttock was made. The piriformis muscle was exposed by the blunt dissection of the gluteus maximus muscle. The sciatic nerve was then exposed under the piriformis muscle [Figure 2]a. The piriformis muscle was tight and tense especially on internal rotation of the hip joint. The piriformis muscle was incised at the tendinons portion with which the tension of the piriformis muscle decreased and compression over the sciatic nerve got relieved [Figure 2]b. There was no apparent pus discharge intraoperatively. After the surgery, she had dramatic relief of pain. She returned to her work as a nurse 2 months after the surgery. Follow-up MR and CT images showed normalized right piriformis muscle [Figure 1]c and d.
Figure 2: Intra - operative photography. After dissecting gluteus maximus muscle, dark - colored and swelled piriformis muscle (a, arrow) entrapped the sciatic nerve. After dissection of the piriformis muscle (b, arrow), sciatic nerve was released (b, arrowheads)

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Chiedozi divided pyomyositis into three stages according depending on the progression of the disease: invasive stage showing myositis without abscess formation, suppurative stage with abscess formation and late stage with sepsis. [4] Pyomyositis in suppurative stage, requires aspiration by the percutaneous route or open drainage. This case illustrates that the possibility of piriformis pyomyositis should be considered in patients with sciatica of undetermined causes, more so when signs of inflammation are present.

 » References Top

1.Filler AG, Haynes J, Jordan SE, Prager J, Villablanca JP, Farahani K, et al. Sciatica of nondisc origin and piriformis syndrome: Diagnosis by magnetic resonance neurography and interventional magnetic resonance imaging with outcome study of resulting treatment. J Neurosurg Spine 2005;2:99-115.  Back to cited text no. 1
2.Chen WS. Sciatica due to piriformis pyomyositis. Report of a case. J Bone Joint Surg Am 1992;74:1546-8.  Back to cited text no. 2
3.Nakai I, Yano Y, Naramatsu M, Hashimoto N. Piriformis syndrome due to piriformis pyomyositis: report of a case. Seikeigeka 2012;63:949-51.  Back to cited text no. 3
4.Chiedozi LC. Pyomyositis. Review of 205 cases in 112 patients. Am J Surg 1979;137:255-9.  Back to cited text no. 4


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