Pyomyositis

Multifokale
Pyomyositis. Hier Darstellung am Unterarm in der MRT. Links T1 FS mit KM mit diffuser Kontrastmittelaufnahme durch den ganzen Unterarm und mehreren putriden Einschmelzungen in der Muskulatur mit randständigem Kontrastmittelsaum. Rechts T2 mit entsprechendem Flüssigkeitssignal in den Einschmelzungen.
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Brucellosis
presenting as piriformis myositis: a case report. Axial short tau inversion recovery (STIR) image; MRI scan taken at the time of antibiotic treatment initiation. The right piriformis muscle is enlarged, bulging anteriorly, with high signal intensity within and loss of definition of its muscle striations, consistent with edema. Compare to the normal piriformis muscle on the left.
jmedicalcasereports.biomedcentral.com • CC-by-2.0
Brucellosis
presenting as piriformis myositis: a case report. Axial spin-echo T1-weighted image with fat suppression with intravenous gadolinium contrast injection; MRI scan taken at the time of antibiotic treatment initiation. The right piriformis muscle enhances avidly after intravenous gadolinium, due to inflammation. Inflammatory changes are also depicted in the adjacent soft tissues of the pelvis.
jmedicalcasereports.biomedcentral.com • CC-by-2.0
Pyomyositis
in a child. Sagittal T2-WI MRI revealing a hyperintense mass around the peroneal bone (arrowheads). Note the diffuse high signal intensity of the tissues surrounding the collection.
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Pyomyositis
in a child. Axial T2-SPIR confirms the presence of a fluid collection involving the flexor hallucis longus, tibial posterior and solear muscles (arrowheads). Note the hyperintensity of the surrounding muscles due to reactive oedema.
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Pyomyositis
in a child. Sagittal (4a), coronal (4b) and axial (4c) T1FS post-gadolinium demonstrates a central hypointensity surrounded by a hyperenhancing rim, confirming the presence of an abscess.
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Pyomyositis
in a child. Coronal T1FS post-gadolinium showing the thick enhancing walls of the abscess. There is also subcutaneous, fascial, and muscular inflammation, as well as osseus enhancement concerning the fibula.
www.eurorad.org • CC by-nc-sa-4.0
Pyomyositis
in a child. Axial T1FS post-gadolinium showing the deep relation of the abcess with the fibula as well as the surrounding muscle enhancement due to inflammation.
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Infectious myositis is an infection of skeletal muscle, and can be acute, subacute, or chronic. Pyomyositis refers specifically to a bacterial infection of skeletal muscle.

Epidemiology

It is most often seen in young adults. Pyomyositis, or bacterial myositis, was once considered a tropical disease but is now seen in temperate climates, particularly with the emergence of HIV infection. Other risk factors for infectious myositis include:

Clinical presentation

Presentation of infective myositis is with pain localized to one or more muscles (although in most cases it is a single muscle), with variable degrees of systemic inflammatory manifestations, depending on the pathogen.

Pathology

Although many pathogens, including viruses, bacteria (including mycobacteria), fungi, and parasites can cause myositis, the most common infectious agent is the bacterium, Staphylococcal aureus, accounting for over 75% of cases .

Radiographic features

Ultrasound

Findings include enlargement of the muscle, with or without abscess formation. Ultrasound may be employed to aid percutaneous drainage of a collection.

CT

Enlargement and decreased attenuation of the affected muscle with effacement and stranding of surrounding fat planes.

If an abscess is present it will appear as an intramuscular fluid collection with peripheral rim-enhancement, the presence of which is helpful in distinguishing focal low density regions from areas of necrosis, which will have little peripheral enhancement.

MRI

MRI is the modality of choice to accurately assessing the extent of involvement. Muscle edema, characterized by high T2 signal is typically present. Abscesses appear, as elsewhere, as fluid collection (high T2, low T1) with peripheral contrast enhancement. There may also be diffuse muscle enlargement.

Treatment and prognosis

Depending on the infective agent systemic antibiotics are administered. If an abscess has formed, then it should usually be drained either surgically or percutaneously.

Potential complications of untreated infectious myositis include:

Differential diagnosis

For MRI appearances consider

See also

Siehe auch:
und weiter:
Assoziationen und Differentialdiagnosen zu infektiöse Myositis:
Septische
Arthritis
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diabetische
Myonekrose
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