Neurosurgery Coding Alert

Tip: Location where the surgeon works is your dependable option.

Coding for trigeminal neuralgia can leave you mystified when you read the operative note. You will need to identify the site and structure that your surgeon is approaching. Make sure you know if your surgeon is targeting the ganglion or the tract. Read on to strengthen you coding skills and earn your deserved payment.

Review Anatomy Basics

Knowing the anatomy will make your code selection very easy. Trigeminal nerve, the largest cranial nerve, is a mixed nerve with a predominant sensory component. It mainly supplies the face through the three branches, i.e. ophthalmic nerve (V1), maxillary nerve (V2), and mandibular nerve (V3). The three nerves converge on the trigeminal ganglion that contains cell bodies of the incoming sensory fibers. Trigeminal ganglion is also called the semilunar ganglion or the gasserian ganglion.

"The gasserian ganglion is a bundle of nerve cells where the trigeminal nerve (CN V) divides into the V1, V2 and V3 nerves. It occupies the Meckel's cave which lies near the apex of the petrous part of the temporal bone," explains Jennifer Schmutz, CPC, health information coder at the Neurosurgical Associates, LLC in Salt Lake City, Utah. From the trigeminal ganglion, the central fibers emerge as a tract and go down through the pons to the medulla to then finally cross the midline in the upper spine and ascend to the brain where the sensations are perceived.

When you are reporting percutaneous treatment of trigeminal neuralgia, you will need to choose from two codes, i.e. 61790 (Creation of lesion by stereotactic method, percutaneous, by neurolytic agent [e.g., alcohol, thermal, electrical, radiofrequency]; gasserian ganglion) and 61791 (Creation of lesion by stereotactic method, percutaneous, by neurolytic agent [eg, alcohol, thermal, electrical, radiofrequency]; trigeminal medullary tract).

"If the lesion is created in the brainstem, then you are going to use 61791, and if it is done in the gasserion ganglion, you will use 61790," explains Schmutz. "One location is the brainstem and the other isn't in the brainstem," she stresses. "The medullary tract lies in the brainstem," adds Teresa Thomas, BBA, RHIT, CPC, practice manager II at St. John's Clinic (Neurosurgery) in Springfield, Missouri. So you can look for the term 'medullary tract' in the operative note to confirm that the surgeon worked in the brainstem.

Look For Procedure Location

Review the note for specific details on where your surgeon created the lesion: in the trigeminal nerve, its ganglion or the nerve tract in the brainstem. "You will decide by the description of the location of the nerve lesion in the surgeon's documentation. Without knowing the location, you would not know the correct code to bill," says Thomas. Your surgeon will commonly approach the gasserion ganglion to destroy the nerve cells so that the patient gets relief from pain. The ganglion is approached through the foramen ovale and the nerve cells are destroyed using chemical or electrical agents or radiofrequency.

Example: If the operative note mentions, "A percutaneous retrogasserian glycerol rhizotomy [PRGR] percutaneous radiofrequency trigeminal gangliolysis (PRTG) was done," you would report code 61790 as the procedures target the gasserian ganglion.

Here's another operative note example:

"After positioning the patient, a C-arm fluoroscopic image intensifier was positioned in the anteroposterior (AP) projection to identify the foramen ovale. Local 1% lidocaine was infiltrated into the skin. The spinal needle was inserted through the cheek and directed toward a point anterior to the external auditory canal and toward the medial aspect of the ipsilateral orbit. Deep injection of 1ml of lidocaine just exterior to the foramen ovale allowed an easy transovale penetration. The location of the needle was confirmed on fluoroscopy and the stylet was removed to observe CSF flow. Sterile nonionic water soluble iodine contrast medium was injected under fluoroscopy to identify the trigeminal cistern and the cistern volume was estimated. The contrast material was evacuated. Sterile undiluted 99.9% anhydrous glycerol mixed with small amounts of sterile radiopaque tantalum dust was slowly injected into the cistern and the proper placement of the glycerol solution was confirmed radiologically as opacity. The needle was removed and the patient transferred to recovery room."

Coding: When trying to treat trigeminal neuralgia by doing a trigeminal tractotomy in the medulla, your surgeon will work at the level of medullospinal junction at the occiput-C1 level. The trigeminal tract is an eloquent target in trigeminal neuralgia. You report code 61791 for such procedures as it is clear that the trigeminal medullary tract and not the ganglion is being approached.

And a third example:

"The patient was placed prone on the CT table. After anesthetizing the skin, a needle was inserted at the occiput-C1 level, 7 to 8 mm lateral to the midline and monitored under imaging. The spinal cord diameter and dura-skin distance were measured. The dura was punctured and CSF flow observed.

The needle was positioned in the posterior aspect of the spinal cord, about one third lateral to the hemicord and the active electrode tip was inserted via the needle. Impedance measurements were taken. Electrical stimulations with low and high frequencies were used to severe the trigeminal tract."

Use Correct ICD Codes

You report 350.1 (Trigeminal neuralgia) as a diagnosis for either 61790 or 61791. You will use ICD-10 code G50.0.