ICD-10 Code G59 – Mononeuropathy in diseases classified elsewhere (2026): Diagnosis, Symptoms & Billing Guide
2026 ICD-10-CM Diagnosis Code G59 – Mononeuropathy in diseases classified elsewhere
What it is
G59 identifies a single-nerve disorder that occurs as a manifestation of another disease. Use it when the mononeuropathy is documented as secondary, not as a primary nerve condition.
Clinical signs
Clinical features vary; refer to documentation. Typical findings may include localized numbness, pain, weakness, or sensory loss in the distribution of one affected nerve.
When to use this code
Use G59 when the record links the mononeuropathy to an underlying disease, and the provider documents that relationship. This code is appropriate when the nerve disorder is not coded as an independent primary diagnosis. Check documentation for the causative condition and any site-specific details.
Do not use for
Do not use G59 for mononeuropathy without a documented underlying disease relationship. Avoid it when the condition is better described by a different neuropathy code or when documentation is unclear.
Coding tip
Code the underlying disease first when instructed by the record, and confirm the causal link before assigning G59.