G59Mononeuropathy in diseases classified elsewhere

G59 is the ICD-10-CM diagnosis code for mononeuropathy in diseases classified elsewhere. It belongs to block G50-G59 (nerve, nerve root and plexus disorders) and chapter 6 (diseases of the nervous system). It is billable, so it can be reported on its own for dates of service from October 1, 2026 through September 30, 2027.

Don't report G59 together with the conditions in its Excludes1 note: diabetic mononeuropathy (E08-E13 with .41), syphilitic nerve paralysis (A52.19), syphilitic neuritis (A52.15) and tuberculous mononeuropathy (A17.83).

Code first: underlying disease.

It is not a CC or MCC, so as a secondary diagnosis it doesn't change the MS-DRG severity level.

In MS-DRG v44.0, it is part of the grouping logic for DRG 073 (Cranial and Peripheral Nerve Disorders with MCC, relative weight 1.5779) and DRG 074 (Cranial and Peripheral Nerve Disorders without MCC, relative weight 1.0173), in MDC 01 (Diseases and Disorders of the Nervous System), as a principal or secondary diagnosis. The DRG a claim lands in depends on the principal diagnosis, procedures and any CC/MCC secondary diagnoses.

It is a manifestation code, so it describes the effect of an underlying disease and can't be the principal diagnosis. Code the underlying condition first.

It has been part of ICD-10-CM since the code set took effect on October 1, 2015 and hasn't changed since.

Before ICD-10, this condition was coded in ICD-9-CM as 355.9 (mononeuritis of unspecified site).