Neurosurgery Coding Alert

Question: What are the differences among the hydrocephalus diagnosis codes in ICD-10?

Tennessee Subscriber

Answer: Here’s a rundown of each specific type of hydrocephalus represented in the ICD-10 code book:

Communicating: Communicating hydrocephalus refers to swelling or enlargement of the brain’s ventricles that occurs due to due to overproduction or defective absorption of cerebrospinal fluid (CSF) and the free flow of CSF between the ventricles and subarachnoid space in the brain. Report this condition with G91.0 (Communicating hydrocephalus).

Obstructive: Obstructive hydrocephalus refers to swelling or enlargement of the brain’s ventricles due to blockage of cerebrospinal fluid (CSF) along one or more narrow pathways that connect the ventricles resulting in increased pressure in the brain. G91.1 (Obstructive hydrocephalus)

(Idiopathic) normal pressure: Idiopathic normal-pressure hydrocephalus refers to swelling or enlargement of the brain’s ventricles due to an abnormal increase of cerebrospinal fluid (CSF), which increases pressure on the brain, characterized by gait disturbance, cognitive issues, and urinary incontinence. The cause of the excess CSF is often not known. Report it with G91.2 ((Idiopathic) normal pressure hydrocephalus).

Post-traumatic: Unspecified post-traumatic hydrocephalus refers to a complication of a traumatic brain injury, which results in overproduction of cerebrospinal fluid (CSF), blockage of CSF, or insufficient absorption of CSF. The provider doesn’t document the trauma that led to the hydrocephalus. Report it with G91.3 (Post-traumatic hydrocephalus, unspecified)

In diseases classified elsewhere: Hydrocephalus in diseases classified elsewhere refers to swelling or enlargement of the brain’s ventricles, which increases pressure on the brain, due to obstruction of cerebrospinal fluid (CSF) flow or absorption associated with another disease. Code the underlying condition before this code. Report it with G91.4 (Hydrocephalus in diseases classified elsewhere). When reporting G91.4, be sure to code first the underlying condition — e.g., congenital syphilis, neoplasm, plasminogen deficiency.

Other: Other hydrocephalus refers to cases when the provider documents a type of hydrocephalus not represented by another code. Report it with G91.8 (Other hydrocephalus).

Unspecified: Unspecified hydrocephalus refers to cases when the provider does not document the type of hydrocephalus that the patient has. Report it with G91.9 (Hydrocephalus, unspecified).