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Interspinales muscles

The interspinales muscles are small, paired, postural muscles located along the vertebral column. They lie in the interspinal spaces, connecting adjacent spinous processes. These muscles are most developed in the cervical and lumbar regions, where spinal mobility is greatest, and less prominent in the thoracic region.

Each interspinalis consists of short vertical fascicles that run between successive spinous processes. They function as segmental stabilizers, assisting in extension of the vertebral column and contributing to fine postural adjustments. Although small in size, they are clinically relevant because they may hypertrophy or degenerate in spinal disorders and can be visualized in high-resolution imaging.

Synonyms

  • Musculi interspinales

  • Interspinal muscles

  • Interspinous stabilizers

Function

  • Aid in extension of the vertebral column when acting bilaterally

  • Contribute to fine motor control and proprioception of individual vertebral segments

  • Provide segmental stabilization of spine during posture and movement

  • Work synergistically with multifidus and other deep intrinsic back muscles

Nerve Supply

  • Supplied by posterior rami of spinal nerves at corresponding vertebral levels

Arterial Supply

  • Cervical region: vertebral artery and deep cervical artery

  • Thoracic region: posterior intercostal arteries

  • Lumbar region: lumbar arteries from the abdominal aorta

Venous Drainage

  • Follows arterial supply:

    • Cervical → vertebral and deep cervical veins

    • Thoracic → posterior intercostal veins

    • Lumbar → lumbar veins → ascending lumbar → azygos system

MRI Appearance

T1-weighted images:

  • Interspinales appear as intermediate signal intensity muscles between adjacent spinous processes

  • Surrounded by hyperintense fat, which improves delineation

T2-weighted images:

  • Muscle tissue shows intermediate-to-low signal

  • Edema, strain, or denervation changes show hyperintense signal

STIR:

  • Suppresses fat, highlighting muscle edema, trauma, or inflammation as bright signal

  • Useful in spinal injury or post-operative evaluation

T1 Fat-Saturated (Pre-contrast):

  • Muscles appear as intermediate signal intensity, easily differentiated from suppressed fat planes

T1 Fat-Saturated Post-Contrast (Gadolinium):

  • Normal muscle enhances mildly and homogeneously

  • Abnormal enhancement indicates myositis, tumor, or infection

MRI Non-Contrast 3D Imaging:

  • Provides detailed 3D visualization of small muscle bundles

  • Useful in surgical planning and post-operative spine imaging

CT Appearance

CT Pre-Contrast:

  • Appears as soft-tissue density between adjacent spinous processes

  • Limited in resolution due to small size, best seen in cervical and lumbar spine

CT Post-Contrast:

  • Muscles may show subtle homogeneous enhancement

  • Useful in detecting infections, tumors, or muscle atrophy

  • 3D reconstructions demonstrate their topographic relation to spinous processes

CT image

interspinales muscles CT coronal image anatomy image -img-00000-00000_00001

MRI image

interspinales muscles MRI coronal image anatomy image -img-00000-00000

MRI image

Interspinales