Hydrocephalus (G91) ICD-10-CM
The G91 code range covers hydrocephalus with 8 ICD-10-CM diagnosis codes. 7 of them are billable and valid for claim submission in fiscal year 2027, and the category headers group them but cannot themselves be billed.
Includes
This note appears immediately under a three character code title to further define, or give examples of, the content of the category.
- acquired hydrocephalus
Type 1 Excludes
A type 1 excludes note is a pure excludes note. It means "NOT CODED HERE!" An Excludes1 note indicates that the code excluded should never be used at the same time as the code above the Excludes1 note. An Excludes1 is used when two conditions cannot occur together, such as a congenital form versus an acquired form of the same condition.
Codes in the G91 Range 8 codes · 7 billable
- G91 HydrocephalusNon-billable
- G91.0 Communicating hydrocephalus
- G91.1 Obstructive hydrocephalus
- G91.2 (Idiopathic) normal pressure hydrocephalus
- G91.3 Post-traumatic hydrocephalus, unspecified
- G91.4 Hydrocephalus in diseases classified elsewhere
- G91.8 Other hydrocephalus
- G91.9 Hydrocephalus, unspecified
Clinical Terms in This Code Range
Definitions from the National Library of Medicine for conditions coded in the G91 range.
Communicating Hydrocephalus
An abnormal accumulation of cerebrospinal fluid within the ventricles of the brain that occurs as a consequence of impaired cerebrospinal fluid reabsorption by the arachnoid granulations.
Hydrocephalus
Excessive accumulation of cerebrospinal fluid within the cranium which may be associated with dilation of cerebral ventricles, INTRACRANIAL HYPERTENSION; HEADACHE; lethargy; URINARY INCONTINENCE; and ATAXIA.
Hydrocephalus, Normal Pressure
A form of compensated hydrocephalus characterized clinically by a slowly progressive gait disorder (see GAIT DISORDERS, NEUROLOGIC), progressive intellectual decline, and URINARY INCONTINENCE. Spinal fluid pressure tends to be in the high normal range. This condition may result from processes which interfere with the absorption of CSF including SUBARACHNOID HEMORRHAGE, chronic MENINGITIS, and other conditions. (From Adams et al., Principles of Neurology, 6th ed, pp631-3)
Non-Communicating Hydrocephalus
An abnormal accumulation of cerebrospinal fluid within the ventricles of the brain that occurs as a consequence of an obstruction at any location within the ventricular system that prevents cerebrospinal fluid flowing into the subarachnoid space.
About the G91 Code Range
Hydrocephalus means too much cerebrospinal fluid collects inside the skull.
The subdivisions distinguish communicating hydrocephalus (G91.0), obstructive hydrocephalus (G91.1), and idiopathic normal pressure hydrocephalus (G91.2). Other codes identify hydrocephalus after trauma (G91.3) or in diseases classified elsewhere (G91.4). The category also has codes for other hydrocephalus (G91.8) and hydrocephalus without a specified type (G91.9).
Questions About This Page
How many billable codes are in the G91 range?
Of the 8 codes in this range, 7 are billable and valid for claim submission from October 1, 2026 through September 30, 2027. Category header codes group them but cannot be reported on claims.
What does the G91 range classify?
The range classifies hydrocephalus. Each code links to its own reference page with billing status, MS-DRG grouping, coding notes, and clinical information.
Related References
Source: CMS FY 2027 ICD-10-CM Tabular List and order file, effective October 1, 2026 through September 30, 2027.
