Investigations of Common Spine Disorders

1. LUMBAGO (Non-Specific Low Back Pain)

Overview

When to Investigate — "Red Flags" First

Ordered Investigations

a) Plain Radiograph (Lumbar Spine — AP + Lateral)

• When to order: Red flags above; NOT for routine lumbago
• Views: AP, lateral; add flexion-extension views if instability suspected
• Findings & Interpretation:
  • Normal in early/acute lumbago
  • Disc-space narrowing, vertebral endplate sclerosis, osteophytes → spondylosis (expected in >90% of people >60 yrs, often asymptomatic)
  • Loss of lumbar lordosis → muscle spasm/degeneration
  • Compression fracture → trauma or pathological (osteoporosis, metastasis)
  • Important caveat: Radiographic spondylosis does not correlate with symptoms

b) MRI Lumbar Spine (modality of choice)

• When to order: Neurological deficit, red flags suggesting malignancy/infection, failure to improve after 4–6 weeks conservative treatment, pre-surgical planning
• T1-weighted: Best for marrow, fat, anatomy
• T2-weighted (workhorse): Disc appears bright (normal). Decreased signal = degenerated/dark disc; annular tear = high-intensity zone (HIZ) — bright focal signal in posterior annulus
• Gadolinium enhancement: Preferred for recurrent disc herniation (distinguishes scar from disc)
• Key findings:
  • Dark disc on T2 → degeneration
  • Posterior disc bulge/herniation
  • Nerve root compression
  • Epidural abscess or tumour enhancement

c) CT Lumbar Spine ± Myelography

• Used when MRI is contraindicated (pacemaker, claustrophobia)
• CT myelogram particularly useful after prior surgery to define bony anatomy
• Better than MRI for bony detail (osteophytes, fracture fragments)

d) Bone Scan (Radionuclide Scintigraphy)

• Sensitive for occult fractures, metastases, infection, Paget's disease
• Low specificity; abnormal in any bony remodelling

e) Blood Tests

• CBC, ESR, CRP → infection or inflammatory arthropathy
• Calcium, phosphate, ALP → metabolic bone disease
• PSA, SPEP → malignancy screen in appropriate context
• HLA-B27 → ankylosing spondylitis (young male, morning stiffness)

2. SCIATICA (Lumbar Radiculopathy / Disc Herniation)

Pathophysiology

Clinical Clues (Guide Investigation)

Investigations

a) Plain Radiograph

• Not diagnostic for disc herniation
• Ordered to exclude fracture, spondylolisthesis, or neoplasm
• Flexion-extension views: detect segmental instability (spondylolisthesis)
• Upright films preferred to simulate load-bearing alignment

b) MRI Lumbar Spine (Gold Standard)

• First-line for sciatica with neurological signs or failure of 4–6 weeks conservative therapy
• T2-weighted sagittal + axial views essential
• Interpret findings with extreme caution: False-positive rate is high — disc bulges are present in asymptomatic individuals; clinical correlation is mandatory
• MRI findings:
  • Posterolateral herniation: Focal protrusion/extrusion of nucleus pulposus with nerve root displacement or compression in the neural foramen
  • Sequestrated disc: Free fragment in epidural space, may migrate superiorly or inferiorly
  • Foramen narrowing: From disc-osteophytic complex, reducing space for exiting nerve
  • Dark disc + HIZ: Degenerated disc with annular tear
• Gadolinium: Use for recurrent herniation post-surgery to differentiate scar tissue (enhances) from disc (does not enhance in acute phase)

c) CT Myelography

• If MRI contraindicated; better bony detail, useful post-surgery

d) Nerve Conduction Studies (NCS) / Electromyography (EMG)

• Ordered when diagnosis uncertain or multiple levels involved
• EMG shows denervation in muscles supplied by affected root (fibrillation potentials, positive sharp waves)
• Useful to distinguish radiculopathy from peripheral neuropathy or plexopathy
• Normal EMG does not exclude radiculopathy (especially if acute)

e) Discography

• Controversial and largely abandoned
• Needle inserted into disc; pain reproduction with contrast injection = concordant pain
• Reserved as pre-operative study to identify pain-generating level
• Evidence suggests needle trauma may accelerate disc degeneration

3. LUMBAR SPONDYLOSIS

Pathoanatomy (Degenerative Spinal Cascade — Kirkaldy-Willis, 1970s)

Investigations

a) Plain Radiograph (AP + Lateral Standing)

• Routine first-line for symptomatic spondylosis
• Findings:
  • Disc space narrowing → degeneration
  • Vertebral endplate sclerosis (sclerosis of subchondral bone at endplates)
  • Osteophytes (bony spurs at disc margins, "traction" or "claw" type)
  • Facet joint changes: Narrowing, sclerosis (osteoarthritis)
  • Spondylolisthesis: Forward slip of one vertebra on another — grade I–IV (Meyerding)
• Flexion-extension views: Detect dynamic instability
• ⚠️ Radiographic spondylosis is near-universal after age 60; its presence alone does not establish it as the pain source

b) MRI Lumbar Spine

• Definitive investigation for neural compression
• T2 dark disc → degeneration; loss of disc height
• Foraminal stenosis → nerve root compression
• Spinal canal diameter on axial T2: Central stenosis if AP diameter <10 mm (absolute), 10–13 mm = relative
• Hypertrophied ligamentum flavum, osteophytes, facet joint effusion contributing to stenosis
• Neurogenic claudication (spinal stenosis): diffuse multilevel changes, "trefoil" or "clover-leaf" canal deformity on axial MRI

c) CT Scan

• Superior to MRI for bony osteophyte detail and canal measurement
• CT myelography: Reveals dynamic compression of nerve roots under contrast

d) Bone Densitometry (DEXA)

• For older patients with vertebral height loss to exclude osteoporotic fracture

e) EMG/NCS

• Confirm lumbar root dysfunction; localize the compressed level

4. CERVICAL SPONDYLOSIS

Pathoanatomy

1. Discogenic neck pain (axial pain)
2. Cervical radiculopathy (root compromise)
3. Cervical myelopathy (cord compression)
4. Myeloradiculopathy (combined)

Investigations

a) Plain Radiograph (Cervical Spine — AP, Lateral, Oblique)

• Findings:
  • Disc space narrowing
  • Osteophytes at Luschka joints and disc margins
  • Foraminal narrowing on oblique views (best seen here)
  • Loss of normal cervical lordosis
  • Vertebral body alignment
• Flexion-extension views: Assess dynamic instability
• Lateral radiograph with measurements:
  • Pavlov's (Torg) ratio: Spinal canal diameter ÷ vertebral body width; <0.8 = congenital stenosis

b) MRI Cervical Spine (Gold Standard)

• T2 sagittal: Disc degeneration (dark disc), disc protrusion, cord signal changes
• T2 axial: Neural foramen narrowing, disc-osteophytic complex
• Key interpretive points:
  • High T2 signal in cord (myelomalacia): Indicates cord damage; prognostic for myelopathy
  • Cord compression: Measured by compression ratio (anteroposterior/transverse diameter); severe <0.4
  • Soft disc herniation: Acute disc bulge without calcification
  • Hard disc/disc-osteophytic bar: Calcified spondylotic bar → more chronic, harder to decompress
  • Gadolinium: Used if tumour, abscess, or demyelination suspected as alternative diagnoses

c) CT ± Myelography

• Better bony osteophyte and foraminal detail than MRI
• CT myelogram: Confirms dynamic nerve root or cord compression; preferred when MRI findings are ambiguous

d) Cervical Radiculopathy — Root Levels & Imaging Correlation

e) EMG/NCS

• Confirm radiculopathy; exclude peripheral causes (carpal tunnel, cubital tunnel)
• Fibrillations in corresponding myotome
• F-waves and H-reflexes: Detect proximal conduction abnormalities
• NCS typically normal in pure radiculopathy (postganglionic sensory fibres are intact)

f) Myelopathy — Additional Investigations

• Upper motor neuron signs (hyperreflexia, Babinski, clonus, Lhermitte's sign) → urgent MRI
• Nurick scale / mJOA score: Quantify myelopathy severity
• Somatosensory evoked potentials (SSEPs): Assess dorsal column function; useful when MRI findings unclear or in follow-up

5. BRACHIAL SYNDROME (Thoracic Outlet Syndrome) & BRACHIAL NEURALGIA

Brachial Syndrome = Thoracic Outlet Syndrome (TOS)

Clinical Tests (Inform Investigation)

• Adson test: Hyperextend neck, rotate to affected side, deep inspiration → diminished radial pulse = vascular TOS
• Roos sign (EAST test): Heaviness or paresthesias in hands after 1 minute arms-up = neurogenic TOS
• Wright's hyperabduction test: Elevated arm → pulse diminished

Investigations

Brachial Neuralgia (Neuralgic Amyotrophy / Parsonage-Turner Syndrome)

Investigations

Summary Table: Investigation of Choice by Disorder

• Plain X-ray → identifies structural deformity, fractures, instability, gross degeneration
• MRI → neural compression, disc pathology, cord signal changes (gold standard for soft tissue)
• CT ± myelography → bony detail, post-surgical anatomy, MRI contraindicated
• EMG/NCS → localise and quantify nerve/root dysfunction, distinguish radiculopathy from plexopathy/peripheral neuropathy
• Vascular studies (Doppler, MRA) → TOS with vascular component