G99.8Other specified disorders of nervous system in diseases classified elsewhere

G99.8 is the ICD-10-CM diagnosis code for other specified disorders of nervous system in diseases classified elsewhere. It belongs to category G99 (other disorders of nervous system in diseases classified elsewhere), block G89-G99 (other disorders of the nervous system) 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.

Within G99, choose G99.8 (Other specified disorders of nervous system in diseases classified elsewhere) only when documentation doesn't support a more specific option: autonomic neuropathy in diseases classified elsewhere (G99.0) and myelopathy in diseases classified elsewhere (G99.2).

Don't report G99.8 together with the conditions in its Excludes1 note: cysticercosis (B69.0), rubella (B06.0-) and syphilis (A52.1-).

Code first underlying disorder, such as: amyloidosis (E85.-) and avitaminosis (E56.-).

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 070 (Other Cerebrovascular Disorders with MCC, relative weight 1.6093), DRG 071 (Other Cerebrovascular Disorders with CC, relative weight 1.0177) and DRG 072 (Other Cerebrovascular Disorders without CC/MCC, relative weight 0.7348), 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 349.89 (other specified disorders of nervous system).