MRI for Scoliosis: Spinal Curvature Assessment

What Is Scoliosis?

Scoliosis is a three-dimensional deformity of the spine involving lateral curvature (sideways bend), rotation of the vertebrae, and changes in the normal front-to-back curves. It's defined as a Cobb angle of 10° or more on a standing X-ray.

The most common type is adolescent idiopathic scoliosis (AIS), which develops during the growth spurt before puberty and has no identifiable cause — "idiopathic" literally means "of unknown origin." AIS accounts for about 80% of all scoliosis cases. It affects girls more frequently than boys, particularly for curves that progress to the point of needing treatment.

Scoliosis affects approximately 2-3% of the UK population (around 1 in 40 adolescents). Of these, about 10% will need some form of treatment, and roughly 0.1-0.3% will need surgery. The ScoliScreen programme doesn't currently operate in all UK schools, so many cases are detected by parents, PE teachers, or GPs.

Other types include congenital scoliosis (caused by vertebral malformation during development), neuromuscular scoliosis (associated with conditions like cerebral palsy or muscular dystrophy), degenerative scoliosis (developing in adulthood due to disc and facet joint degeneration), and syndromic scoliosis (associated with conditions like Marfan syndrome or neurofibromatosis).

Why MRI Is Used for Scoliosis

X-ray is the primary imaging tool for scoliosis — it shows the curve pattern and Cobb angle on a standing full-spine film. MRI serves a different, complementary role:

• Detecting intraspinal abnormalities: MRI identifies abnormalities within the spinal cord and canal that may be causing or associated with the scoliosis. These include syringomyelia (a fluid-filled cavity within the spinal cord), Chiari malformation (descent of the cerebellar tonsils through the foramen magnum), tethered cord, spinal cord tumours, and diastematomyelia (split cord).
• Atypical curve patterns: Left thoracic curves (bending to the left in the chest region) are atypical for AIS and raise suspicion of an underlying cause. MRI is strongly recommended in these cases.
• Young age of onset: Scoliosis presenting before age 10 has a higher prevalence of associated intraspinal abnormalities. MRI is recommended for all early-onset scoliosis.
• Rapid progression: A curve that's progressing faster than expected warrants MRI to exclude an underlying cause.
• Neurological symptoms or signs: Asymmetric reflexes, weakness, abnormal sensation, or absent abdominal reflexes in a patient with scoliosis indicate possible spinal cord pathology.
• Pre-surgical planning: Before scoliosis correction surgery, MRI of the entire spine ensures there are no unexpected intraspinal abnormalities that could complicate surgery or be harmed by instrumentation.
• Congenital scoliosis: MRI delineates the vertebral anomalies (hemivertebrae, block vertebrae, unsegmented bars) and identifies associated spinal cord abnormalities — present in about 20-40% of congenital scoliosis cases.

MRI Sequences Used

• T1-weighted sagittal of the entire spine: Provides an anatomical overview of the spinal cord, vertebral bodies, and disc spaces from the foramen magnum to the sacrum. The spinal cord is visible as a structure within the CSF-filled thecal sac.
• T2-weighted sagittal of the entire spine: CSF appears bright, providing excellent contrast against the spinal cord. Syrinx cavities (fluid within the cord) appear as bright areas matching CSF signal. Disc degeneration, herniations, and spinal canal stenosis are well-visualised.
• T1 and T2 axial through regions of interest: Targeted axial images through any areas that look abnormal on sagittal views, or through the entire cord if screening for subtle abnormalities.
• STIR sagittal: Sensitive to bone marrow oedema and soft tissue inflammation. Useful for detecting vertebral fractures, infection, or inflammatory spondylitis that may be contributing to the deformity.
• T1 with gadolinium contrast (if indicated): Used when there's suspicion of a spinal cord tumour, infection, or inflammatory process. Post-contrast images show enhancing (actively abnormal) tissue.
• Coronal images: Particularly useful in congenital scoliosis for delineating vertebral anomalies and their relationship to the spinal cord.
• Cine/phase-contrast CSF flow study: If Chiari malformation is found, this dynamic sequence assesses CSF flow at the foramen magnum — restricted flow may indicate the need for surgical decompression.

What Radiologists Look For

• Syringomyelia: A fluid-filled cavity (syrinx) within the spinal cord, appearing as a bright area on T2-weighted images matching CSF signal. Present in approximately 5-20% of scoliosis patients referred for MRI. A large or expanding syrinx may need treatment (often addressing an associated Chiari malformation) before scoliosis correction surgery.
• Chiari malformation: Descent of the cerebellar tonsils more than 5mm below the foramen magnum. Often associated with syringomyelia. Classified as type I (tonsillar descent only) or type II (associated with myelomeningocele).
• Tethered cord: The conus medullaris (the lower end of the spinal cord) normally terminates at or above the L1-L2 disc level. A low-lying conus with a thickened filum terminale suggests tethering, which may contribute to progressive scoliosis and neurological symptoms.
• Spinal cord tumours: Intramedullary tumours (within the cord, such as astrocytoma or ependymoma) or intradural extramedullary tumours (e.g. neurofibroma) can present with scoliosis, particularly in neurofibromatosis.
• Congenital vertebral anomalies: MRI shows the soft tissue and neural elements associated with hemivertebrae, butterfly vertebrae, or unsegmented bars that X-ray alone can't reveal.
• Disc assessment: In adult/degenerative scoliosis, MRI evaluates disc degeneration, herniations, and foraminal stenosis contributing to pain and neurological symptoms.
• Cord signal abnormalities: Any abnormal signal within the cord itself — oedema, gliosis, or myelomalacia — suggesting compression or intrinsic pathology.

How to Prepare for the Scan

• No fasting required unless contrast is planned
• Wear comfortable clothing without metal — no bras with underwires, no jeans with metal buttons
• If a spinal brace is worn, it will need to be removed for the scan
• For younger children who may struggle to lie still, sedation or general anaesthesia may be arranged — this needs advance planning with the MRI department
• Bring any previous X-rays or scan reports, as these help the radiologist focus on areas of concern

What Happens During the Scan

Whole spine MRI requires you to lie on your back for 40-60 minutes. This is one of the longer MRI protocols because the entire spine — from the base of the skull to the sacrum — needs to be covered.

The scanner acquires images in overlapping segments that are stitched together. You'll lie still throughout, with earplugs or headphones. The table may move slightly between segments.

For children and teenagers, having a parent or carer visible through the scanner window (or in the room, after safety screening) can help. Some centres provide video goggles or music to make the experience more manageable.

The scan is performed lying down, which means the scoliosis may appear less severe than on standing X-rays — the curve partially corrects when gravity is removed. This is expected and doesn't reduce the scan's diagnostic value for assessing the spinal cord and canal.

What MRI Can't Show

• True standing curve magnitude: Scoliosis is measured on standing X-rays because the curve's severity is gravity-dependent. Lying-down MRI consistently underestimates the Cobb angle. X-ray remains the standard for curve measurement and progression monitoring.
• Bony detail: For detailed bone anatomy (e.g. pedicle morphology for surgical screw planning, or subtle vertebral anomalies), CT provides superior cortical bone visualisation.
• Curve flexibility: Bending films (side-bending X-rays) show how much the curve corrects, which influences surgical planning. MRI doesn't provide this information.
• Skeletal maturity: Risser sign (iliac crest apophysis ossification), hand bone age, and triradiate cartilage status — all assessed on X-rays — predict remaining growth and therefore the risk of curve progression. MRI doesn't routinely assess these.

Treatment Pathways After Diagnosis

• Observation: Curves under 25° in growing children are monitored with X-rays every 4-6 months. Once growth is complete, small curves rarely progress.
• Physiotherapy (Schroth method or SEAS): Scoliosis-specific exercises can help manage symptoms, improve posture, and may slow curve progression in mild-to-moderate curves, though evidence for preventing the need for bracing or surgery is still developing.
• Bracing: For curves between 25-40° in growing patients, a rigid brace (typically a Boston or Chêneau type) worn 18-23 hours per day can prevent curve progression during the growth spurt. The BrAIST study showed bracing reduced the progression rate from 48% to 28%.
• Vertebral body tethering (VBT): A newer, growth-modulating surgical option for skeletally immature patients. A flexible cord is attached to screws on the convex side of the curve, allowing continued growth on the concave side. Available at a few specialist centres in the UK.
• Spinal fusion surgery: For curves over 45-50° (or rapidly progressing curves despite bracing). Metal rods and screws are attached to the vertebrae, the curve is corrected, and bone graft encourages the vertebrae to fuse together. Results are generally excellent, with significant curve correction and good long-term outcomes.
• Treatment of underlying cause: If MRI reveals syringomyelia with a Chiari malformation, foramen magnum decompression may be needed before addressing the scoliosis. A tethered cord requires surgical untethering.

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