Neurosurgery Coding Alert

How do you tell the difference between 61790 (Creation of lesion by stereotactic method, percutaneous, by neurolytic agent [e.g., alcohol, thermal, electrical, radiofrequency]; gasserian ganglion) and 61791 (... trigeminal medullary tract)?

That's the question a Neurosurgery Coding Alert reader posed when she wrote, "What is the differencebetween the gasserian ganglion and trigeminal medullary tract, and how do you determine which code to use?" The answer lies in knowing your anatomy so you can assign codes accordingly.

Understanding the nerve branches and how they relate to each other is your first step in distinguishing between 61790 and 61791. Here's what you need to know:

• The trigeminal nerve provides sensation to the face. It's the fifth (and largest) cranial nerve, also called the fifth nerve or simply V.

• The trigeminal nerve nucleus is in the brain stem. The trigeminal nerve root stems from the nucleus and ends at the gasserian ganglion. Your physician might refer to this as the trigeminal ganglion or semilunar ganglion.

• The trigeminal nerve splits into three major branches, or divisions, from the ganglion. They are the ophthalmic nerve (V1), maxillary nerve (V2), and mandibular nerve (V3).

You'll typically report 350.1 (Trigeminal neuralgia) as a diagnosis for either 61790 or 61791.

Once you understand the nerve locations, let your physician's documentation point you to the correct code:

• "Lesions of the gasserian ganglion are performed through the foramen Ovale and are coded with 61790," says Gregory Przybylski, MD, director of neurosurgery at the New Jersey Neuroscience Institute, JFK Medical Center in Edison.

• "Code 61791," Przybylski adds, "describes the medullary tract, so it is a brainstem lesion rather than a nerve lesion."

Rena Hall, CPC, with Kansas City Neurosurgery Group in Missouri, agrees. "If the provider mentions a medullary tract, then your correct choice would be 61791," she says.

The Correct Coding Initiative (CCI), version 15.3, went into effect Oct. 1 and couples 61790 and 61792 with three moderate sedation codes:

• 99148 -- Moderate sedation services (other than those services described by codes 00100-01999), provided by a physician other than the health care professional performing the diagnostic or therapeutic service that the sedation supports; younger than 5 years of age, first 30 minutes intra-service time

• 99149 -- ... age 5 years or older, first 30 minutes intra-service time

• +99150 -- ... each additional 15 minutes intraservice time (List separately in addition to code for primary service).

"Sedation is typically performed by an anesthesiologist in the operating room because of risk of bradycardia and hypotension on injection," Przybylski says. That means the moderate sedation edits probably won't affect your coding, but check your surgeon's documentation to verify. The edits carry a modifier indicator of "0," meaning you can't append a modifier to split the edit and report both services.