MRI of the Sacral Spine is a special examination to produce a high-quality image of the anatomy of the sacral spine and the joints and other soft tissues between the pelvis and spine, the spinal canal, the nerve root, and surrounding soft tissue. The sacral area (sacrum) is located between the lowest lumbar vertebra and the tailbone, helps to transfer weight from the body, connects the spine to the pelvic bones, and plays a role in transporting the lower part of the body.

MRI is generally the study of choice for sacral spine disorders, due to its excellent soft tissue contrast and lack of exposure of the patient to ionizing radiation.

Procedure for MRI of the Sacral Spine

Before the Scan

• A thorough medical history and symptom evaluation are carried out.
• Notify radiology staff of metal implants or other objects retained from the body, such as surgical wires and pacemakers.
• Take off all metal objects, such as jewelry, watches, belts, and hair accessories.
• Contrast may require a fast.
• If it is necessary, patients with claustrophobia can be sedated.

During the Scan

• The patient is comfortably seated on the MRI bed, with the area to be scanned (the sacral region) inside the MRI machine's imaging coil.
• Movement may be minimised with the use of cushions and positioning aids.
• Multiple gestures are processed in different views, like axial, sagittal, and coronal.
• Some special sequences (for example, fat suppression) can enhance detection of lesions.
• Contrast material may be injected into the veins through the skin during the examination if needed.
• This will usually take between 20 and 40 minutes.

After the Scan

• The patients are expected to walk right after surgery.
• If contrast material was given, enough fluids should be provided to ensure adequate hydration.
• The images are read by a radiologist who then writes a thorough report for the referring doctor.

MRI Sequences Used

T1-Weighted Imaging

• Offers good bone marrow and anatomical detail.
• Useful to recognize any fracture, fatty marrow changes, and marrow replacement diseases.

T2-Weighted Imaging

• Demonstrates involvement of fluid-filled structures and soft tissue abnormalities.
• Helpful in the diagnosis of edema, cysts, and inflammatory changes.

STIR (Short Tau Inversion Recovery)

• Prevents fat overload and will reveal any subtle bone marrow and soft tissue edema.
• Very useful in the diagnosis of metastatic diseases, inflammation, and trauma.

Contrast-Enhanced T1 Imaging

• Aids in recognizing tumors, infections, and active inflammation.
• Helps to differentiate between recurrent disease and postoperative scar tissue.

Diffusion-Weighted Imaging (DWI)

• Determines the movement of water within tissues.
• Of value in the diagnosis of small tumours, abscesses, and some inflammatory lesions.

Conditions Commonly Diagnosed

Sacral Insufficiency Fractures

Common in the elderly and those with osteoporosis – bone marrow edema and fracture lines.

Chordoma

A slowly developing malignant tumour that usually develops in the centre of the sacral area, which may also involve bone destruction and infiltration of soft tissues.

Metastatic Disease

Secondary cancers from other organs, like breast, prostate, or lung cancer, where MRI examination may have picked up the cancer before a normal examination that might have been done.

Ankylosing Spondylitis

A chronic inflammation of the sacroiliac joints, which can be diagnosed at the earliest stage through MRI before changes are apparent on X-ray.

Infectious Sacroiliitis

Bacterial or tubercular infection of the sacroiliac joint, which leads to inflammation and swelling of the marrow and sometimes to a sacroiliac abscess.

Tarlov Cysts

Cysts (fluid-filled nerve root sheaths which can sometimes press on nerves and cause symptoms).

Tethered Cord and Other Congenital Disorders

Congenital defects of the lower part of the spinal cord and the sacral area, which could produce neurological symptoms.

Benefits of MRI of the Sacral Spine

• Preferably soft tissue, nerve, and bone marrow visualization.
• No exposure to ionising radiation.
• The multiplanar images will be used for a full anatomical evaluation.
• Early diagnosis of tumors, infection, inflammatory diseases, and fractures.
• Excellent separation of the active disease from chronic changes.

Limitations

• Images may be compromised by patient movement.
• In some cases, metallic implants will be the reason for image distortion.
• There are very rare allergic reactions associated with the giving of contrast.
• Kidney Function Assessment may be necessary before contrast-enhanced studies.
• Patients who experience fear of closed spaces may experience claustrophobia during the exam.

Patient Preparation Tips

• Select comfortable clothes that do not contain metal.
• If you are undergoing a procedure that requires contrast, follow any directions you have to fast.
• Let the radiology staff know about implants, previous surgery, or any area of the spine that has suffered injuries.
• Try to keep quiet while you have the scan; the more motionless you are, the better the image quality will be.

Conclusion

In the lower back region, the MRI of the Sacral Spine is very helpful for imaging bones, joints, nerves, and muscles. It is an essential diagnostic tool because of its early detection of fracture, tumour, infection, inflammatory disease, or congenital defect. MRI imaging provides detailed imaging without the use of radiation to help guide the care professional towards a diagnosis and treatment plan, monitor the progression or recovery of a disease, and enhance patient outcomes.