Neurosurgery Coding Alert

Remember 3 key steps: Fossa, dura, and approach.

Coding for intracranial access may be confusing as the procedures may be complicated by multiple surgical steps that your surgeon may do. You will need to adopt a focused approach to make your way to definitive codes for all surgical steps. Carefully read through the operative note to find out what your surgeon precisely did. 

Here are some examples that can help you build skills you need for coding the skull base approach procedures. 

Confirm the Fossa Site

The first step in reporting skull base surgeries is to confirm in the operative note the lesion location. 

What is a fossa? A fossa is a hollow or depressed area. The skull is divided into anterior, middle, and posterior fossae.

“There are three different primary compartments in the skull,” says Gregory Przybylski, MD, director of neurosurgery at the New Jersey Neuroscience Institute, JFK Medical Center, Edison. “The anterior fossa contains structures that include the frontal lobes (orbital level), the middle fossa contains structures that include the temporal lobes (above the auditory canal), and the posterior fossa contains structures that include the cerebellum and brainstem.”

Make your way to the right fossa: Look for terms in the note such as ‘craniofacial’ or ‘orbitocranial’ approach and terms referring to the bones of the face like ethmoid, sphenoid, maxilla, and others to help confirm that the approach is through the anterior cranial fossa. Also, note that the frontal lobe of the brain lies in the anterior cranial fossa, so the term ‘frontal’ is a cue for the anterior cranial fossa approach.  In contrast, the temporal lobe lies in the middle fossa, whereas the cerebellum and brainstem are located in the posterior fossa.

Look for Dura Access

Once you have confirmed the fossa where the pathology lies, read through the operative note to confirm if the dura was opened up for excision of the intracranial lesion. The anterior approaches are either intra- or extra-dural. “In contrast to anterior fossa approaches, the surgical skull base approaches to the middle and posterior fossa do not include separate codes based on whether the dura is opened or not,” Przybylski says.

Example 1: You report 61582 (Craniofacial approach to anterior cranial fossa; extradural, including unilateral or bifrontal craniotomy, elevation of frontal lobe(s), osteotomy of base of anterior cranial fossa) when the surgeon approaches through the anterior cranial fossa and works outside the dura. You would use 61583 (Craniofacial approach to anterior cranial fossa; intradural, including unilateral or bifrontal craniotomy, elevation or resection of frontal lobe, osteotomy of base of anterior cranial fossa) when the surgeon works through the dura to approach and lift the frontal lobe of the brain through a craniotomy in the overlying frontal bones.

“One of the reasons for differentiating intradural from extradural approaches to the anterior fossa is that lesions in this area may originate from facial or sinus structures rather than from the intracranial intradural contents,” Przybylski says.  “The extradural approaches may be performed by a variety of surgical specialties including otolaryngology and neurosurgery.”

Determine the Approach

Look for the details that specify whether the surgeon used a transfacial or transcranial approach. Your surgeon may utilize the facial approach to perform a graduated greater exposure depending upon the extent of the disease. The basic approach may involve a lateral rhinotomy along with a low craniotomy. “Keep in mind that there are a variety of craniotomy codes that may be applicable for the type of lesion being treated.  The skull base approach codes should only be considered when significant tissue dissection and bony removal are required to achieve access to the skull base,” Przybylski says. 

Crucial: Look at what is being removed. Orbital exenteration implies 61585 (Orbitocranial approach to anterior cranial fossa, extradural, including supraorbital ridge osteotomy and elevation of frontal and/or temporal lobe[s]; with orbital exenteration). You submit this code when your surgeon removes the entire orbit, in contrast to just the superior part of orbit in 61584 (Orbitocranial approach to anterior cranial fossa, extradural, including supraorbital ridge osteotomy and elevation of frontal and/or temporal lobe[s]; without orbital exenteration).

Another possible approach is through a LeFort osteotomy which is a horizontal incision into the bone at the base of the maxilla above the apices of the teeth. The distinct code for this approach is 61586 (Bicoronal, transzygomatic and/or LeFort I osteotomy approach to anterior cranial fossa with or without internal fixation, without bone graft). You choose a definitive code for anterior cranial fossa depending on the location of the lesion.

Example: If you read that the surgeon incised a cm above gum line, from third molar of one side to that on another side and identified the location of bone cuts above roots of teeth extending from the piriform aperture to the pterygoid plates, you should pick up the hint for a Lefort osteotomy and hence report code 61586. You report the same code if the surgeon adopts the bicoronal or transzygomatic approach. “This procedure includes a variety of different approaches that includes internal fixation, if performed, but does not include bone grafting,” Przybylski says.

Interpret These Examples of Operative Notes

Read the example of an operative note below and list the codes that you will report.

Operative note 1: 

“A bicoronal scalp incision was made 2 to 3 cms behind the hairline and the flap elevated in the subgaleal plane down to the eyebrows, laterally to the lateral orbital walls and medially just below the nasal glabella. The supratrochlear and supraorbital neurovascular bundles were exposed and preserved and the anterior cranial fossa exposed by removing a segment of bone. The dura was then dissected off the crista galli and cribriform plate dividing the dural sleeves along the olfactory nerves. The intracranial portion of the tumor was then assessed which was found to involve the dura. The dura was then resected together with the tumor. The dura was repaired with fascia lata. Using the lateral rhinotomy incision, the periosteum was elevated from the nasal bone and from the medial and inferior surfaces of the orbit. The nasolacrimal duct and the ethmoidal arteries were identified and secured. The tumor was resected after a complete enbloc ethmoidectomy. The defect in the anterior cranial fossa was closed with the pericranium. The spinal drain was clamped, the frontal sinus obliterated, and the patient was given a nasal pack.” 

Operative note 2:  

“A bicoronal skin incision was performed without including the temporalis fascia or pericranium. A pericranial flap, from one temporal line to another, was lifted and extended around 10 cm posteriorly. The zygomatic process was exposed after cutting the temporalis fasciae bilaterally. Using the standard Weber-Fergusson incision, the lip was split and a lateral rhinotomy was made in the nose with the incisions extending into the conjunctival fornix superiorly and inferiorly while preserving the eyelids for orbital reconstruction. After turning the flap, a bifrontal craniotomy and then a bifrontal supraorbital osteotomy with right zygomatic osteotomy was done. Using a subfrontal extradural approach, the microscope revealed the tumor breeching the cribiform plate and affixed to the dura.  The tumor extended intradurally, prompting excision of the tumor involving the dura with subsequent repair.”