Nerve root dysfunction arising from the sacral or sacrococcygeal spinal segments, producing pain, sensory changes, or motor deficits in the distribution of sacral nerve roots (S1–S5) or the coccygeal nerve.

Documentation tips

What should appear in the chart to support M54.18.

Source · Editorial brief grounded in 5 cited references ↓

• Provider must explicitly identify the sacral or sacrococcygeal region as the site of nerve root involvement — vague terms like 'lower back radiculopathy' default to M54.17 (lumbosacral) or M54.16 (lumbar), not M54.18.
• Document the specific sacral nerve root level(s) implicated (e.g., S3, S4) when known; this supports medical necessity for targeted injections and distinguishes the diagnosis from lumbosacral radiculopathy.
• Record objective neurological findings: dermatomal sensory loss in the perineal or posterior thigh distribution, reduced anal or bladder sphincter tone, or weakness in muscles innervated by lower sacral roots.
• Include relevant imaging findings — MRI evidence of sacral foraminal stenosis, sacral nerve root compression, or sacrococcygeal pathology — to support the radiculopathy diagnosis and justify procedural billing.
• If the patient has a concurrent disc disorder at a lumbar or sacral level, do not add M54.18; instead use M51.1- (radiculopathy with lumbar/other disc disorder) per the Excludes1 convention at the M54.1 parent level.

Related CPT procedures

Procedure codes commonly billed with M54.18. 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 M54.18 and adjacent codes.

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

• Assigning M54.18 when the documented site is 'lumbosacral' — that maps to M54.17, not M54.18. Reserve M54.18 for pathology the provider explicitly locates at the sacral or sacrococcygeal level.
• Using M54.18 alongside a lumbar or sacral disc disorder code — the Excludes1 note under M54.1 prohibits coding M54.1x when radiculopathy is attributable to an intervertebral disc disorder; use M51.1- instead.
• Defaulting to M54.18 when the specific sacral region is undocumented — M54.10 (site unspecified) is technically correct in that scenario, though it creates a weaker claim and risks denial for spine procedures.
• Confusing M54.18 with M53.3 (sacrococcygeal disorders, NEC) or M53.88 (other specified dorsopathies, sacral/sacrococcygeal) — M54.18 requires documented nerve root involvement, not just local joint or soft-tissue pathology.

Clinical context

Source · Editorial summary grounded in 5 cited references ↓

Sibling codes

Other billable codes under M54.1 (laterality / anatomic variants).