C5-C6 Disc Space Narrowing: Clinical Manifestations and Complications
Neurological Symptoms from Foraminal Stenosis
C5-C6 disc space narrowing causes progressive reduction in intervertebral foraminal size, with 1mm of disc height loss reducing foraminal area by 20-30%, 2mm causing 30-40% reduction, and 3mm resulting in 35-45% reduction, directly compressing the C6 nerve root. 1
Radicular Symptoms (C6 Nerve Root Compression)
- Arm pain and numbness radiating down the lateral forearm to the thumb and index finger in a C6 dermatomal pattern 2
- Motor weakness affecting biceps, wrist extensors, and potentially finger extensors 2
- Sensory deficits including numbness and tingling in the C6 distribution 2, 3
- Scapular pain that may accompany the radicular symptoms 2
Myelopathic Symptoms (When Cord Compression Occurs)
- Bilateral hand weakness and clumsiness affecting fine motor control and grip strength 4
- Gait disturbance or lower extremity weakness when spinal cord compression is present 4
- Hyperreflexia with positive Hoffmann sign and ankle clonus bilaterally 5
- Sensory level changes or patchy sensory deficits below the level of compression 4
- Bladder dysfunction in severe cases with significant cord compression 5
- Progressive quadriparesis in extreme cases, particularly if there is associated disc herniation with cord edema 5
Degenerative Changes and Associated Findings
MRI findings of disc space narrowing should be interpreted cautiously, as degenerative changes are common in patients over 30 years and correlate poorly with symptoms in isolation. 6
Structural Complications
- Foraminal stenosis develops proportionally to disc height loss, with 3mm vertical reduction associated with severe neuroforaminal narrowing 1
- Posterior disc protrusion may accompany disc space narrowing 6
- Anterior compression of the dura and spinal cord can occur with progressive degeneration 6
- Osteophyte formation at the disc margins as part of the degenerative cascade 6
Progressive Degenerative Features
- Facet arthropathy commonly develops at the same level, though correlation with symptom lateralization is poor 6
- Vacuum phenomenon may be visible on imaging 6
- Joint capsular calcification in advanced cases 6
Critical Clinical Pitfalls
The most important pitfall is assuming that imaging findings of disc space narrowing automatically explain a patient's symptoms—only 34% of patients with progressive cervical disc degeneration on MRI develop symptoms over 10 years. 6
Diagnostic Considerations
- Cervical spine pathology may mimic or exacerbate thoracic outlet syndrome, requiring careful differentiation 7
- Isolated finger drop is inconsistent with C5-C6 level pathology and suggests C6 or C7 radiculopathy from a different level, or peripheral nerve pathology 4
- Spinal cord edema at C4/C5 or C5/C6 should manifest with bilateral symptoms, not isolated unilateral findings 4
Risk Factors for Symptom Development
Patients who develop symptoms from disc space narrowing show more frequent progression of:
- Disc degeneration on serial imaging 6
- Anterior dural compression 6
- Posterior disc protrusion 6
- Foraminal stenosis 6
Rare but Serious Complications
Intradural disc herniation at C5-C6, though extremely rare (0.27% of all disc herniations), can cause progressive quadriparesis and represents a neurosurgical emergency. 5