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Superficial transverse perineal muscle

The superficial transverse perineal muscle is a paired, slender band of skeletal muscle in the perineum. It forms part of the superficial perineal pouch and plays a stabilizing role in the pelvic floor. Each muscle extends transversely across the perineum from the ischial ramus to the perineal body. Though relatively small, it is clinically important for pelvic stability and continence, and it may be encountered in perineal trauma, obstetric injury, and pelvic reconstructive surgery.

Synonyms

  • Transversus perinei superficialis

  • Superficial transverse perineal muscle of the pelvic floor

Origin, Course, and Insertion

  • Origin: Arises from the inferior ramus of the ischium near the ischial tuberosity

  • Course: Runs medially and slightly anteriorly across the superficial perineal pouch, lying just below the pelvic diaphragm and above the perineal membrane

  • Insertion: Attaches into the perineal body (central tendon of perineum), where it interdigitates with its contralateral partner and other perineal muscles

Relations

  • Anteriorly: Bulbospongiosus muscle and root of penis/clitoris

  • Posteriorly: External anal sphincter and superficial external anal vessels

  • Superiorly: Perineal membrane and deep transverse perineal muscle

  • Inferiorly: Perineal skin and superficial perineal fascia (Colles’ fascia)

Function

  • Stabilizes and supports the perineal body

  • Reinforces the pelvic floor by anchoring perineal muscles

  • Contributes to the integrity of the urogenital triangle

  • Plays a minor role in continence and pelvic stability during locomotion and straining

Clinical Significance

  • Can be disrupted during obstetric trauma (perineal tears)

  • Targeted in episiotomy repair and pelvic reconstructive surgery

  • Weakness or damage may contribute to pelvic floor dysfunction

  • May be evaluated on pelvic MRI in cases of incontinence or trauma

MRI Appearance

T1-weighted images:

  • Appears as a thin band of low-to-intermediate signal intensity

  • Fat of the ischiorectal fossa and perineal region appears bright, enhancing visualization

  • Hemorrhage or fibrosis may alter normal signal

T2-weighted images:

  • Normal muscle shows low-to-intermediate signal

  • Perineal fat is bright, providing contrast

  • Injury, edema, or inflammation may show bright signal within the muscle

STIR (Short Tau Inversion Recovery):

  • Normal muscle is low signal

  • Perineal fat suppressed (appears dark)

  • Pathology (strain, inflammation, trauma) appears as bright hyperintensity

T1 Fat-Sat Post-Contrast:

  • Normal muscle enhances mildly and uniformly

  • Inflammatory changes enhance more intensely

  • Abscess shows rim enhancement with non-enhancing core

CT Appearance

Non-Contrast CT:

  • Muscle appears as thin soft tissue density within perineum

  • Surrounded by fat of ischiorectal fossa (low density)

  • Hematoma appears as focal hyperdense area

Post-Contrast CT:

  • Normal muscle enhances mildly and uniformly

  • Inflammatory or neoplastic lesions appear as irregular enhancement

  • Abscess demonstrates central low attenuation with rim enhancement

MRI image

Superficial transverse perineal muscle MRI axial anatomy image-img-00000-00000

MRI image

Superficial transverse perineal muscle MRI axial anatomy image-img-00000-00000