G91.4Hydrocephalus in diseases classified elsewhere

G91.4 is the ICD-10-CM diagnosis code for hydrocephalus in diseases classified elsewhere. It belongs to category G91 (hydrocephalus), 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 G91 (hydrocephalus), G91.4 is specifically for hydrocephalus in diseases classified elsewhere. Related codes cover communicating hydrocephalus (G91.0), obstructive hydrocephalus (G91.1), (Idiopathic) normal pressure hydrocephalus (G91.2), post-traumatic hydrocephalus, unspecified (G91.3), other hydrocephalus (G91.8) and unspecified (G91.9).

Don't report G91.4 together with the conditions in its Excludes1 note: hydrocephalus due to congenital toxoplasmosis (P37.1).

Code first underlying condition, such as: congenital syphilis (A50.4-), neoplasm (C00-D49) and plasminogen deficiency (E88.02).

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 056 (Degenerative Nervous System Disorders with MCC, relative weight 2.2655) and DRG 057 (Degenerative Nervous System Disorders without MCC, relative weight 1.2838), 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 331.7 (cerebral degeneration in diseases classified elsewhere).