Anterior Subarachnoid Space Effacement at C5-C6: A Red Flag for Cervical Myelopathy

Complete effacement of the anterior subarachnoid space at C5-C6 with possible minimal cord deformation is an MRI finding indicating severe narrowing or obliteration of the CSF-filled space in front of the spinal cord at the C5–C6 vertebral level. This implies significant ventral (anterior) compression of the spinal cord.

Anatomy Context

The subarachnoid space surrounds the cord with CSF, providing cushioning. Anteriorly, it’s bordered by the posterior longitudinal ligament and vertebral bodies/discs. Effacement means this protective buffer is lost.

Common Causes

• Cervical disc herniation (most common): nucleus pulposus protrudes posteriorly
• Cervical spondylosis: osteophytes, disc bulging, ligamentum flavum hypertrophy
• OPLL (ossification of posterior longitudinal ligament)
• Trauma: acute disc extrusion, fracture-dislocation
• Tumor/metastasis: vertebral body or epidural
• Epidural hematoma/abscess

Clinical Significance

"Possible minimal cord deformation" suggests early compressive myelopathy risk. Symptoms may include:

• Neck pain, radiculopathy (C6: thumb/index finger, wrist extensors)
• Myelopathic signs: gait imbalance, hand clumsiness, hyperreflexia, Babinski, sensory loss
• Lhermitte’s sign (electric shock on neck flexion)

Management

• Asymptomatic + minimal deformation: serial MRI/neurological exams
• Progressive myelopathy or significant compression: surgical decompression (ACDF, corpectomy, laminoplasty)
• Neurosurgical/orthopedic spine consultation mandatory

This finding is a red flag for cervical myelopathy—even if currently asymptomatic. Timely intervention prevents irreversible cord injury.