Inflammation of one or more intervertebral discs in the cervical spine region, where the specific etiology has not been documented or confirmed.

Documentation tips

What should appear in the chart to support M46.42.

Source · Editorial brief grounded in 6 cited references ↓

• Specify 'cervical region' by name — do not rely on anatomical shorthand like 'C-spine'; payers and coders need the exact region documented to justify M46.42 over adjacent codes like M46.41 (occipito-atlanto-axial) or M46.43 (cervicothoracic).
• Record the imaging modality and findings that support the diagnosis — MRI signal changes at the disc level, endplate erosion, or contrast enhancement on gadolinium sequences are the most common objective anchors.
• Document why the etiology is unspecified: note pending culture results, atypical presentation, or inconclusive biopsy to justify using the 'unspecified' variant rather than a more specific infectious code.
• If surgical intervention is planned or performed, include documentation of failed conservative measures (antibiotics, immobilization, pain management) to satisfy medical necessity criteria for cervical fusion under CMS Article A59668.
• Note the specific cervical levels involved (e.g., C5-C6 disc) to support accurate operative report coding and to distinguish single-level from multi-level pathology for procedure code selection.

Related CPT procedures

Procedure codes commonly billed with M46.42. Linking the right diagnosis to the right procedure is what establishes medical necessity.

Source · CMS LCDs · AAOS specialty guidance · claims-pattern analysis

Common coding pitfalls

The recurring mistakes coders make with M46.42 and adjacent codes.

Source · Editorial brief grounded in CDC ICD-10-CM tabular guidance, AAOS coding references, and cited references ↓

• Using M46.42 when the etiology is already confirmed as pyogenic — that requires M46.32, not M46.42; payers auditing infectious spondylopathy claims will flag the mismatch.
• Confusing cervical region (M46.42) with cervicothoracic region (M46.43) — if the disc involved spans the C7-T1 junction, the cervicothoracic code applies.
• Failing to add a secondary code for the causative organism when culture results return positive — M46.42 can coexist with a B-code (e.g., bacterial agent) but should be reassessed for upgrade to M46.32 once etiology is confirmed.
• Coding M46.42 as the sole diagnosis when vertebral osteomyelitis is also present — M46.22 should be added as a separate code to fully capture the extent of infection.
• Applying M46.40 (unspecified site) instead of M46.42 when the cervical region is clearly documented — M46.40 is a non-billable parent code and will be rejected by payers requiring site specificity.

Clinical context

Source · Editorial summary grounded in 6 cited references ↓

Sibling codes

Other billable codes under M46.4 (laterality / anatomic variants).