Accessory Muscles Causing Neurovascular Compromise


Identify the presence of an accessory muscle 








 Munib Sana

Panel Chair

 Jay Patti

Panel Reviewers

 Musculoskeletal Panel


 Creative Commons 4.0

Status  Public Commenting

Clinical Implementation

Value Proposition

Accessory muscles are common, and while typically asymptomatic, they can sometimes be pathologic. They can mimic soft-tissue tumors and cause pain or compressive neuropathy. They are also easily overlooked on MRI, even by musculoskeletal (MSK) radiologists. An algorithm that can identify the presence of an accessory, anomalous, or supernumerary muscle would be valuable as this is an often-overlooked source of a patient’s symptoms.


A 30-year-old female has elbow and hand pain. An MRI of the elbow is ordered. An algorithm detects the presence of an accessory muscle and alerts the radiologist of the categorization at the time of interpretation.

Workflow Description

Images obtained from MRI are sent to PACS and the AI engine. The axial T1 MRI image is analyzed by the AI. Accessory muscle is categorized as present or absent. A message is sent to PACS from the engine with the classification information. If the value is classified as “present,” then the radiologist is alerted.

Considerations for Dataset Development

Procedures(s): MRI: Elbow, Forearm, Hand, Wrist, Ankle, Knee

Sex at Birth: {Male, Female}


Age: [0,90]


Elbow: {Accessory anconeus, Accessory head of the flexor pollicis longus}


Abnormalities: {soft tissue mass, subcutaneous edema}

Clinical Note: Soft-tissue mass or subcutaneous edema in the posteromedial elbow could be misclassified as an accessory anconeus.


Interventions: {prior surgery, ulnar nerve transposition surgery}

Clinical Note: If the patient has had prior surgery, there could be scar tissue in the posteromedial elbow. Additionally, the patient could have already undergone ulnar nerve transposition surgery, in which case the presence of an accessory anconeus is either known and/or irrelevant.


Hand and wrist: {Accessory flexor digitorum superficialis indicis, Accessory abductor digiti minimi, Extensor digitorum brevis manus}


Forearm: {FCR brevis vel profundus,  Accessory ECR brevis, Accessory ECR intermedius, Accessory ECR accessories}


Knee: {Accessory slip of the medial head of the gastrocnemius, Accessory slip of the lateral head of the gastrocnemius, Aberrant origin of the medial head of the gastrocnemius, Aberrant origin of the lateral head of the gastrocnemius, Tensor fascia suralis, Accessory popliteus}


Ankle: {Peroneus tertius, Peroneus quartus, Peroneus accessories, Peroneocalcaneus externum, Peroneus digiti minimi, Flexor digitorum longus, Peroneocalcaneus internus, Accessory Soleus, Tibiocalcaneus internus}

Technical Specifications




MRI, Elbow

Data Type




Body Region

Upper Extremity

Anatomic Focus



Primary Outputs

Accessory Muscle

RadElement ID



Presence of accessory muscle

Data Type


Value Set






Public Commenting

Use cases are meant to be a primary vehicle for distributing clinical information to the developer community. They pinpoint precise scenarios within radiology workflows where potential automation could add noticeable value and establish standards for interpreting and passing corresponding common data elements. Implementing effective standards requires the perspective from all stakeholders. So to that end, we encourage your feedback on use cases.

To submit comments, please email with the use case title(s) and relevant comments by January 1, 2019. If more convenient, you may also download this use case and comment directly on the PDF. Just attach the PDF copy on the email.