mrimaster

Lumbosacral Plexus MRI Protocol and planning

Indications for lumbosacral plexus MRI scan

lumbosacral plexus anatomy

The lumbosacral plexus is a complex network of nerves that arises from the lumbar and sacral spinal nerves (L1 to S4) and supplies the lower extremities, pelvis, and some parts of the abdominal wall. It is formed by the intertwining and branching of multiple nerves, and its main function is to provide motor and sensory innervation to the lower limbs and pelvis. Here’s an overview of the major nerves and components of the lumbosacral plexus:

  1. Lumbar Plexus (L1-L4): The lumbar plexus is the upper portion of the lumbosacral plexus and is formed by the ventral rami of the first four lumbar nerves (L1 to L4). It lies within the psoas major muscle and gives rise to several important nerves, including:
  • Iliohypogastric nerve (L1): Provides motor innervation to the transversus abdominis and internal oblique muscles, and sensory innervation to the skin of the lower abdomen.
  • Ilioinguinal nerve (L1): Supplies the skin of the upper medial thigh, the mons pubis, and the labia majora in females or the root of the penis and scrotum in males.
  • Genitofemoral nerve (L1-L2): Divides into two branches – the genital branch, which supplies the cremaster muscle in males and sensory innervation to the scrotum or labia majora, and the femoral branch, which provides sensory innervation to the skin of the upper anterior thigh.
  • Lateral femoral cutaneous nerve (L2-L3): Supplies sensory innervation to the lateral thigh.
  • Femoral nerve (L2-L4): The largest nerve of the lumbar plexus, it provides motor innervation to the quadriceps femoris muscle group, sartorius, and iliacus muscles, and sensory innervation to the anterior thigh and medial leg and foot.
  1. Sacral Plexus (L4-S4): The sacral plexus is the lower portion of the lumbosacral plexus and is formed by the ventral rami of the last lumbar nerve (L4) and the sacral nerves (S1 to S4). It lies on the posterior aspect of the pelvis and gives rise to the following major nerves:
  • Superior gluteal nerve (L4-S1): Supplies the gluteus medius, gluteus minimus, and tensor fasciae latae muscles, which are responsible for hip abduction and medial rotation.
  • Inferior gluteal nerve (L5-S2): Innervates the gluteus maximus muscle, responsible for hip extension and lateral rotation.
  • Sciatic nerve (L4-S3): The largest nerve in the body, it is formed by the fusion of the ventral rami of L4 to S3. The sciatic nerve runs down the posterior thigh and divides into two terminal branches – the tibial nerve and the common fibular (peroneal) nerve.
  • Tibial nerve (L4-S3): Supplies the posterior thigh muscles and almost all the muscles in the leg and foot, controlling ankle plantar flexion and foot inversion.
  • Common fibular (peroneal) nerve (L4-S2): Divides into the superficial fibular nerve and the deep fibular nerve. It controls dorsiflexion of the foot and the muscles of the anterior and lateral leg.

Contraindications

Patient preparation for lumbosacral plexus MRI scan

Positioning for lumbosacral plexus MRI

Recommended Lumbosacral Plexus MRI Protocols and Planning

Lumbosacral Plexus MRI Localizer

MRI urography positioning photo

A three-plane localizer must be taken at the beginning to localize and plan the sequences. Localizers are normally less than 25 seconds and are T1\T2-weighted low-resolution scans.

lumbar pluxues MRI localiser image

T2 tse sagittal 3mm

Plan the sagittal slices on the coronal plane and angle the planning block parallel to the spinal cord. Check the positioning block in the other two planes, ensuring an appropriate angle is given in the axial plane (parallel to the center of the vertebral body and the spinous process). Verify the position block in the sagittal plane; the field of view (FOV) must be big enough to cover the entire lumbosacral plexus from L1 down to the pubic symphysis (normally 350mm). Ensure that the slices are sufficient to cover the nerves from the right acetabulum to the left acetabulum. The phase direction should be head to feet to avoid motion artifacts from the abdomen.

Parameters

TR

4000-5000

TE

100-120

SLICE

3 MM

FLIP

130-150

PHASE

H>F

MATRIX

448X384

FOV

350-350

GAP

10%

NEX(AVRAGE)

2

T1 tse coronal 3mm

Plan the coronal slices on the sagittal plane; angle the planning block parallel to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left psoas muscle). Check the positioning block in the sagittal plane; FOV must be big enough to cover the whole lumbosacral plexus from L1 down to the pubic symphysis (normally 350mm). Slices must be sufficient to cover the nerves from the anterior border of the symphysis pubis to the median sacral crest. Adding a saturation band in front of the coronal block will reduce artifacts from breathing and peristalsis.

planning mri lumbosacral plexus coronal scans

Parameters

TR

400-600

TE

15-25

SLICE

3 MM

FLIP

150

PHASE

R>L

MATRIX

512X380

FOV

350-350

GAP

10%

NEX(AVRAGE)

2

T2 STIR coronal 3mm

Plan the coronal slices on the sagittal plane; angle the planning block parallel to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left psoas muscle). Check the positioning block in the sagittal plane; FOV must be big enough to cover the whole lumbosacral plexus from L1 down to the pubic symphysis (normally 350mm). Slices must be sufficient to cover the nerves from the anterior border of the symphysis pubis to the median sacral crest. Adding a saturation band in front of the coronal block will reduce artifacts from breathing and peristalsis.

planning mri lumbosacral plexus coronal scans

Parameters

TR

4000-5000

TE

110

FLIP

160

NEX

2

SLICE

3 MM

MATRIX

384X320

FOV

350-350

PHASE

R>L

GAP

10%

TI

150

T2 space 3D 1mm isotropic coronal

Plan the coronal 3D block on the sagittal plane; angle the planning block parallel to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left psoas muscle). Check the positioning block in the sagittal plane; FOV must be big enough to cover the whole lumbosacral plexus from L1 down to the pubic symphysis (normally 350mm). Slices must be sufficient to cover the nerves from the anterior border of the symphysis pubis to the median sacral crest. Adding a saturation band in front of the coronal block will reduce artifacts from breathing and peristalsis.

MRI lumbosacral plexus coronal 3d scan planning

Parameters

TR

2000-3000

TE

90-100

SLICE

1MM

FLIP

160-170

PHASE

R>L

MATRIX

384X320

FOV

330-350

GAP

10%

NEX(AVRAGE)

2

T1 TSE Axial 3mm SFOV

Plan the axial slices on the sagittal plane; angle the planning block perpendicular to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane (perpendicular to the lumbar spines). Slices must be sufficient to cover the lumbosacral plexus from L1 down to the pubic symphysis.

planning mri lumbosacral plexus axial scans

Parameters

TR

400-600

TE

15-25

SLICE

3 MM

FLIP

150

PHASE

R>L

MATRIX

384X320

250-300

GAP

10%

NEX(AVRAGE)

2

T2 stir Axial 3mm SFOV

Plan the axial slices on the sagittal plane; angle the planning block perpendicular to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the coronal plane (perpendicular to the lumbar spines). Slices must be sufficient to cover the lumbosacral plexus from L1 down to the pubic symphysis.

planning mri lumbosacral plexus axial scans

Parameters

TR

4000-5000

TE

110

FLIP

150

NEX

2

SLICE

3 MM

MATRIX

320X320

FOV

250-300

PHASE

R>L

GAP

10%

TI

150

Contrast enhanced lumbosacral plexus

Use T1 TSE Fat saturated axial and coronal scans after the administration of IV gadolinium DTPA injection(copy the planning outlined above). The document below provides access to the recommended dosage of gadolinium DTPA injection, as advised by the manufacturer.

Optional Scans

T1 VIBE DIXON 3D 1mm isotropic coronal post contrast

Plan the coronal 3D block on the sagittal plane; angle the planning block parallel to the spinal canal. Check the positioning block in the other two planes. An appropriate angle must be given in the axial plane (parallel to the right and left hip joint). Check the positioning block in the sagittal plane; FOV must be big enough to cover the whole lumbosacral plexus from L1 down to the pubic symphysis (normally 350mm). Slices must be sufficient to cover the nerves from the anterior border of the symphysis pubis to the median sacral crest. Adding a saturation band in front of the coronal block will reduce artifacts from breathing and peristalsis.

MRI lumbosacral plexus coronal 3d scan planning

Parameters

TR

6-7

TE

2.39 4.77

SLICE

1 MM

FLIP

12

PHASE

A>P

MATRIX

384X384

FOV

330-350

GAP

10%

NEX(AVRAGE)

2