40-year-old female patient with acute regional forearm pain and flexor compartment swelling following the second unit of a blood transfusion (transfusion was immediately stopped). An emergency fasciotomy was then performed. While the swelling resolved, the patient continued to lose function corresponding to all flexor and some extensor arm muscles.
Axial T1 weighted image shows (Fig. 1) evidence of a fasciotomy and loss of fat planes but no appreciable intrinsic muscle abnormality while the T2 weighted fat saturated image (Fig. 2) shows widespread oedema represented by extensive high signal involving almost all of the flexor compartmental muscles as well as some of the muscles in the extensor compartment and surrounding soft tissues. On T1 post contrast fat suppressed images (Fig. 3, 4), there is widespread non enhancement involving almost all of the flexor compartment musculature and well as some of the extensor compartment musculature. Flow void as well as contrast enhancement is observed within the surrounding subcutaneous veins indicating satisfactory venous drainage (Fig. 4) and therefore implying some intact arterial supply. There were no clinical or biochemical features to suggest any infection making intramuscular abscesses unlikely. Therefore a regional non-infective myonecrosis was considered the most likely diagnosis.
Myonecrosis is a term referring to death of muscle and can occur in a number of situations. On MRI, it is characterised by non enhancement of muscle. Perifascial fluid collections, subcutaneous oedema, peripheral enhancement of muscle following contrast have also been described as adjunctive MRI findings [1].
Among the many causes of myonecrosis include diabetic myonecrosis [2, 3, 5], chronic graft versus host disease (GVHD) [3], various drug overdoses (e.g. heroin, cocaine, barbiturates [4]), sickle cell crises, crush injuries, severe ischaemia, intra-arterial chemotherapy and various conditions causing rhabdomyolysis.
Focal (or regional) myonecrosis has been described following compartmental syndrome but usually occurs before a fasciotomy or when a fasciotomy has been delayed [3].
An unusual feature in this case is that the myonecrosis extends beyond one compartment (i.e. involves both the flexor and extensor compartments) which implies that a pure compartment syndrome could not have been the sole causative factor.
Rhambdomyolysis has previously been reported to occur with heparin [3] which may have been a possible contributor in this case especially considering the patient receiving a blood transfusion immediately prior to the event, although this is not proven in this case.
Regional myonecrosis
Based on the provided MRI images, the following main features are observed:
These findings correlate with the patient’s postoperative clinical condition (emergency fasciotomy for compartment decompression): although acute swelling has subsided, muscle function is still impaired, and there is concern for a significant degree of muscle necrosis.
Taking into account the patient’s history (acute forearm swelling, interrupted blood transfusion, urgent fasciotomy for decompression) and the imaging findings, the following considerations arise:
In this case, the MRI shows widespread absence of enhancement and abnormal signals in the muscles, suggesting muscle fiber necrosis. The injury may be secondary to multiple causes, such as severe local ischemia, rhabdomyolysis, or compartment syndrome. Based on the clinical picture, myonecrosis is the primary consideration.
Although an emergency fasciotomy has been performed, if the surgical decompression was insufficient or the tissues were compressed for too long, irreversible muscle fiber necrosis may still occur. The current imaging suggests the necrosis extends beyond a single muscle compartment, indicating more extensive involvement.
The use of certain medications (e.g., heparin) or other factors (including metabolic disorders, transfusion-related complications, or ischemia-reperfusion injuries) may trigger rhabdomyolysis, resulting in localized muscle necrosis and functional impairment. On MRI, the necrotic areas may also present local or diffuse abnormal muscle signals.
Considering the patient’s age, the acute onset, clinical history (blood product transfusion, sudden local swelling, fasciotomy for decompression), and MRI findings showing obvious muscle necrosis with heterogeneous enhancement over a wide range, the most likely diagnosis is:
“Acute Myonecrosis”
The imaging results and clinical course indicate that the necrosis is not limited to a single compartment but also involves part of the extensor compartment, consistent with severe or multifactorial causes. This case may involve compartment syndrome combined with other contributing factors (e.g., rhabdomyolysis, adverse reactions to blood products or medications).
After the acute inflammatory or necrotic phase, initiate functional rehabilitation and physical therapy promptly, with gradual progression and individualization:
Throughout the rehabilitation process, regularly evaluate postsurgical recovery as well as neurovascular function. Discontinue and re-evaluate if severe pain or localized swelling occurs again.
Disclaimer: This report is a reference analysis based on the current patient history and imaging data provided. It does not replace in-person evaluation or professional medical advice. If there are additional clinical concerns or changes in symptoms, prompt medical consultation or further specialized examinations are recommended.
Regional myonecrosis
