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| Year : 1999 | Volume
: 47
| Issue : 4 | Page : 324-6 |
Pyomyositis - clinical and MRI characteristics report of three cases.
Meena AK, Rajashekar S, Reddy JJ, Kaul S, Murthy JM
Departments of Neurology, Radiology and Imageology, Nizam's Institute of Medical Sciences, Panjagutta, Hyderabad, 500082, India.
Correspondence Address:
Departments of Neurology, Radiology and Imageology, Nizam's Institute of Medical Sciences, Panjagutta, Hyderabad, 500082, India.
We report three patients with pyomyositis due to Staphylococcus aureus. Magnetic resonance imaging aided in the accurate diagnosis of the infection and of the extent of involvement. Incision, drainage and antibiotic therapy eradicated the infection in all the patients. We suggest clinical or subclinical bacteraemic seeding of the diseased muscle, as the most likely mechanism for pyomyositis.
How to cite this article:
Meena A K, Rajashekar S, Reddy J J, Kaul S, Murthy J M. Pyomyositis - clinical and MRI characteristics report of three cases. Neurol India 1999;47:324 |
Pyomyositis is a primary infection of striated muscles and occurs most often in healthy men. Traquar[1] credited Virchow for the earliest mention of pyomyositis. However, first true description was probably by Scriba in 1885.[2] It is most commonly reported from tropical countries and is responsible for 1 to 2 per cent of surgical admissions to hospitals in some tropical countries.[3],[4] The disorder is rare in temperate zones, but has recently been recognized with increasing frequency, particularly in individuals with human immunodeficiency virus infection (HIV).[5],[6],[7],[8],[9],[10] Pyomyositis has rarely been reported from India.[11],[12] This report describes three patients with magnetic resonance image (MRI) features.
Case 1 : A 23 year old pregnant woman was admitted with high-grade fever with chills and painful swelling of left thigh of 10 days duration. On physical examination she was febrile and toxic. Left thigh was diffusely tender, swollen, tense, warm, and indurated without overlying erythema. Investigations showed a total leukocyte count of 19,600/cumm, with 82% neutrophils. ESR was 75 mm in the first hour and CK was 112U/L. Multiple blood cultures were sterile. Ultrasonogram of the left thigh showed a large hypoechoic lesion in the quadriceps muscle with few thickened internal septae and the margins were illdefined. Muscles in the anterior compartment of left thigh showed high signal intensity rims on T1 weighted images [Figure - 1] which were uniformly hyperintense on T2 weighted images [Figure 2a].
The abscess was drained and the pus grew Staphylococcus aureus sensitive to augmentin, amikacin, cloxacillin and cephataxime. The patient was started on intravenous cephalexin before culture report was available and she made steady recovery.
Case 2 : A 25 year old male was seen for fever and painful swellings of right thigh, back of left thigh, and right shoulder of 10 days duration. Fever was high-grade associated with chills and rigors. On examination he was ill and febrile. [Right] thigh was diffusely tender, swollen, warm and fluctuant. Posterior part of left thigh was diffusely tender, swollen, warm, tense and indurated. [Right] deltoid was swollen, tender, warm, and slightly indurated. Investigation showed a total leukocyte count of 15,800/cumm with 85% neutrophils. ESR was 82 mm in the first hour and CK was 58 U/L. Ultrasound examination revealed diffuse enlargement of muscles with preserved intermuscular fat planes in the anterior aspect of right thigh. Muscle fibers were not identifiable and low levels of echoes were seen in the place of muscle fibers.
Muscle groups in the right shoulder anteriorly and left thigh posteriorly were enlarged and hypoechoic with preserved muscle fibers. Multiple high-signal-intensity rims were seen in the muscles of posterior compartment of left thigh on T1 weighted images. T2 weighted images showed hyperintense signals with focal fluid collection [Figure 2b]. Pus from left thigh abscess grew Staphylococcus aureus sensitive to augmentin and cloxacillin. He was given intravenous cloxacillin. There was steady improvement.
Case 3 : An 11 year old boy was seen for pain and swelling of the left forearm of 4 days duration. Two days later he developed painful swellings in the right leg and left thigh. On the day of admission he had difficulty to lift head off the bed. He had moderate grade fever without chills and rigors. Patient was not on any immunosuppressive medication. On examination he was anaemic, febrile and alert. Tender warm swellings were present in the right calf, left thigh, and left forearm. The swelling in the left forearm was fluctuant. Investigations showed a hemoglobin of 10.5 gm/dl and total leukocyte count of 15,000/cumm with 85% neutrophils. Erythrocyte sedimentation rate (ESR) was 60 mm in the first hour. Serum creatine kinase (CK) was 435 IU/l. Blood and pus from the abscess grew Staphylcoccus aureus sensitive to cefataxime and augmentin. T1 weighted MRI of right gastroenemius muscle showed high-signal-intensity rim which was uniformly hyperintense on T2 weighted images.
He was given intravenous cefataxime along with supportive care. The abscess in the left forearm was drained. On the fourth admission day he developed tachypnoea. Chest examination revealed bilateral coarse crepitations more on the left side. Augmentin was added. He showed steady recovery.
Pyomyositis typically presents as a localized infection of muscle, beginning with pain and swelling. The diagnosis is often overlooked or delayed because most physicians are not familiar with the entity. Local signs of inflammation, fever, leukocytosis and elevated erythrocyte sedimentation rate are common features.[3],[4],[5],[8] The CK may be normal or mildly elevated.5 The involved muscles may eventually develop a firm, wooden texture on palpation. Later, an abscess may form as the muscle becomes fluctuant. Any skeletal muscle can be involved, but large muscles of the lower extremities are commonly affected. Multiple muscle involvement, as seen in two of our cases, occurs in 12-60% of patients.[3],[4],[8],[9],[11],[13] One of our patients developed septicaemia and bronchopneumonia during the course of the illness. Blood cultures are positive in about 30% of patients.[14] Pneumonitis with abscess or pleural thickening is seen in 5% of the cases of tropical pyomyositis.[15] At autopsy microscopic evidence of bronchopneumonia has been documented in 50% of patients.[16] Toxic shock syndrome is the other serious complication described in association with pyomyositis.[17]
Most patients do well with appropriate intravenous antibiotics; a fatal outcome is rare. Early recognition during presuppurative phase allows prompt antibiotic treatment and rapid resolution of the muscle infection without surgical drainage.[18] Newer imaging modalities particularly gallium scanning, ultrasonography, CT scan and magnetic resonance imaging (MRI) have greatly facilitated early recognition.[19],[20],[21] MRI is superior to CT and ultrasonography in the detection and characterization of lesion(s) in pyomyositis. During early "invasive" phase of the disease, CT and ultrasonographic features may not be specific. However, ultrasonography is particularly useful to monitor progression from presuppurative phase to suppurative phase, and also to guide the area of drain. On the T1-weighted MR images, pyomyositis is suggested by a high-signal-intensity rim. It is probably produced by paramagnetic material such as methaemoglobin from subacute haemorrhage, bacterial or macrophage sequestration of iron, and/or free radicals that shorten the T1 of tissue in the periphery.[22] MRI also proved valuable in differentiation of the intramuscular inflammatory infiltrate of early `invasive' phase of pyomyositis (with focal areas of increased intensity on T2 weighted images) from muscle abscesses of later stages (with its rim of increased signal intensity around the abscesses on T1-weighted images).[20],[21],[22]
The exact pathogenesis of pyomyositis is uncertain. Clinical or subclinical involvement of skeletal muscle can occur in some of the conditions associated with tropical and nontropical pyomyositis. Tropical pyomyositis is occasionally described in association with previous blunt muscle trauma, nutritional deficiencies and parasitic infections.[23],[24] Nontropical pyomyositis typically affects those immunocompromised by HIV infection,[5],[6],[7],[8],[9] malignant disease, diabetes mellitus, dermatomyositis, or other debilitating illnesses.[5],[8],[24] All our patients were otherwise immunocompetent individuals. In 90% of the cases Staphylococcus aureus is the incriminating organism.[5],[23],[25] In a patient with rapidly progressive generalized pyomyositis, muscle biopsy specimen revealed a myopathy with multiple areas of muscle fiber necrosis surrounded by neutrophils and mononuclear inflammatory cells and gram positive cocci.[13] These observations suggest bacteraemic seeding of diseased muscle as the most likely pathogenesis for pyomyositis.
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