Neurosurgery Coding Alert

Any one of 14 codes (61580-61598) can describe the approach during skull-base surgery. Applying the appropriate code is complicated not only by the number of choices and the difficult terminology involved but because more than one approach may be required -- or because elements of several approaches may be combined. Payment for these procedures ranges from a high of 77.16 relative value units (RVUs), or about $3,000 on average, to a low of 46.39 RVUs, or about $1,800, according to Medicare's 2001 Physicians Fee Schedule. Therefore, inaccurate coding can alter reimbursement significantly.

 
The skull base is the foundation of the cranium-- a thick, complex structure on which the brain rests, and which separates the brain from the remainder of the head, face and neck. The approach for skull-base surgeries, which are usually performed to remove a tumor on the undersurface of the brain, gains access to one of three areas: the anterior (frontal) cranial fossa (61580-61586), middle (temporal) cranial fossa (61590-61592), or posterior (cerebellur) cranial fossa (61595-61598). The anterior fossa lies approximately above the eyes. The middle fossa, an irregularly shaped area resembling a butterfly and centered on the pituitary gland, encompasses the temporal lobes of the brain. The posterior fossa rests below the brainstem and cerebellum.
 
"The surgeon may access any of the fossae via one of several entry points," says Vallo Benjamin, MD, professor of neurosurgery at New York University. Because different entry points can lead to the same destination, however, the direction of dissection -- rather than the point of entry -- determines which internal structures are revealed and therefore dictates initial code selection. In simple terms, when first choosing the code, the destination matters more than how you got there.
 
Ideally, the surgeon will clearly dictate in the operative report the fossa(e) he or she approached. Alternatively, the coder may apply his or her knowledge of anatomy to determine the area(s) of the skull base accessed and narrow the code selection accordingly. The location of the tumor (or other reason for surgery) -- which should always be documented -- can provide guidance. For instance, the documentation might specify, "A tumor at the clivus was approached via the sphenoid sinus." The clivus lies just in front of the brain stem, toward the rear of the skull, and is therefore located in the rear portion of the middle cranial fossa. In this case, the correct approach code should be chosen from the 61590-62592 range. Always confer with the surgeon if documentation is unclear or if there is any doubt that the proper code range has been selected.

Intra- or Extradural?

 
The next step in narrowing code selection is to determine whether the dissection occurs intra- or extradurally. The dura is the thick membrane surrounding the brain that maintains cerebrospinal fluid (CSF) pressure. An intradural approach requires that the membrane be cut, releasing the CSF. If "intradural" or "extradural" is not specified, the coder may look further in the documentation for evidence of a watertight closure following the eventual definitive procedure (e.g., "The dura was repaired"), which is necessary to restore CSF pressure if an intradural approach is performed.
 
Mobilized Structures Dictate Final Code Choice

 
When the fossa to be accessed and intra- or extradural dissection have been determined, final code selection depends on the precise internal structures exposed or mobilized. This can be problematic because surgeons may not always use CPT terminology or reference the precise anatomic landmarks specified in the code descriptors (e.g., petrous carotid artery, petrosal or sigmoid sinus, etc.). In addition, a single approach may combine elements defined by several descriptors. Physician education is the long-term solution, says Patricia Murtif, billing specialist at City Neuroscience in Grove City, Ohio, but unclear documentation or unfamiliar terminology may require that the surgeon be consulted prior to claim submission.

Anterior Fossa Approaches

 
Anterior approaches are divided into three main categories:
 

Craniofacial: The craniofacial approach (61580-61583) involves an incision along the nose (rhinotomy) to expose the frontal bone, usually to access the olfactory or optic nerves, or the area surrounding the pituitary gland. The nose, forehead and/or orbits may be resected. Entry to the skull occurs via the anterior (frontal, ephmoid, sphenoid or maxillary) sinuses. If the operative report describes, for instance, "approach through ephmoid sinus," these are the codes to consider, Murtif says.
 
If no bone is removed (i.e., osteotomy) from the anterior fossa, select either 61581 (craniofacial approach to anterior cranial fossa; extradural, including lateral rhinotomy, orbital exenteration, ethmoidectomy, sphenoidectomy, and/or maxillectomy) or 61580 (... without maxillectomy or orbital exenteration). These are both extradural procedures, the more extensive of which (61581) includes removal of the contents of the orbit (the bony cavity in which the eye rests) or even a portion of the orbit, and/or removal of the maxillary sinus (just below the nose and/or above the front teeth).
 
If osteotomy is indicated (the rear floor of the anterior fossa may be removed to gain better access to other internal structures), choose 61582 (... extradural, including unilateral or bifrontal craniotomy, elevation of frontal lobe[s], osteotomy of base of anterior cranial fossa) or 61583 (... intradural ... ), depending on whether the dura is entered. These procedures generally involve lifting the frontal lobe(s) of the brain to remove bone from the base of the anterior fossa, which -- if described in the documentation -- provides an additional clue that these are the proper codes.
 

Orbitocranial: These extradural approaches (61584-61585) involve osteotomy of and entry through the supraorbital ridge, immediately above the eye, as well as elevation of the frontal or temporal lobe(s). Select 61584 (... without orbital exenteration) if the contents of the orbit are left intact or 61585 (... with orbital exenteration) if they are wholly or partially removed.
 

Bicoronal, transzygomatic and/or LeFort I osteotomy: Code 61586 (bicoronal, transzygomatic and/or LeFort I osteotomy approach to anterior cranial fossa with or without internal fixation, without bone graft) describes an approach either by incision along the eyes with removal of the zygoma (i.e., through the cheek bone) or by fracturing the maxilla (beneath the nasal cavity). This is a "catchall" code, in that these are dissimilar approaches in totally separate anatomic areas. Because necessary bone is removed during each, however, repair following the procedure for which the approach is made may include use of wires, plates or screws to reattach the zygoma or maxilla. According to Murtif, "Evidence of such repair in the documentation (e.g., 'the zygomatic bone was secured with wire & ') provides verification that 61586 is correct."

 
Middle approach codes describe one of two basic procedures:
 

Infratemporal: Codes 61590 (infratemporal pre-auricular approach to middle cranial fossa ... ) and 61591 (... postauricular... ) describe an approach through the temporal bone, either in front of (preauricular) or behind (postauricular) the ear. This distinction provides the most obvious clue as to which code is appropriate. And, to improve access when entering in front of the ear, the surgeon may dislocate the lower jaw (mandible). If this is noted in the operative report, the proper code is likely 61590. Mobilization of the facial nerve implies 61590, while mobilization of the contents of the auditory canal (specifically the ossicular chain) suggests 61591. Note that either of these approaches may include resection of the orbits, sinus, temples and posterior cheekbones and decompression/mobilization of the petrous carotid artery.
 

Orbitocranial zygomatic: This approach (61592, orbitocranial zygomatic approach to middle crania fossa [cavernous sinus and carotid artery, clivus, basilar artery or petrous apex] including osteotomy of zygoma, craniotomy, extra-or intradural elevation of temporal lobe) is similar to that described by 61586. The cheekbone is removed (osteotomy of zygoma), but the surgeon progresses back -- toward the middle fossa -- rather than forward toward the anterior fossa. This code includes intra- or extradural elevation of the temporal lobe to reach the underlying structures.

Posterior Fossa Approaches
 
 
Each code in this category describes a unique approach, although all may include resection of the temple, anterior and posterior ear, orbits, mandible and mastoid (behind and slightly below the ear), according to the Coders' Desk Reference.
 

Transtemporal: For this, the simplest posterior approach (61595, ... jugular foramen or midline skull base, including mastoidectomy, decompression of sigmoid sinus and/or facial nerve, with or without mobilization), the surgeon enters through the temporal bone behind the ear (similar to 61591), progressing rearward. Absent the additional procedures described by the remaining posterior approach codes, 61595 is likely the appropriate choice.
 

Transcochlear: The distinguishing feature of 61596 (transcochlear approach ... including labyrinthectomy, decompression, with or without mobilization of facial nerve and/or petrous carotid artery) involves removal of vital ear structures, including the timpanic bone, labyrinth and cochlear. Hearing is usually lost in this type of approach, and therefore it is not often performed.
 

Transcondylar: The transcondylar approach (61597, [far lateral] approach ...including occipital condylectomy, mastoidectomy, resection of C1-C3 vertebral body[s], decompression of vertebral artery, with or without mobilization) is easily identified because it is the only one to include resection of vertebral bodies. The point of entry is the occipital bone, low and to the side of the back of the skull.
 

Transpetrosal: Entry with 61598 (transpetrosal approach ... clivus or foramen magnum, including ligation of superior petrosal sinus and/or sigmoid sinus) is lower on the occipital bone than that indicated with 61597. This is the only approach to involve ligation (binding or tying) of sinuses.

 
Sometimes, multiple approaches are necessary. A tumor, for instance, can spread beyond the confines of a single fossa, requiring more than one approach to access the affected areas and complete the definitive procedure. If this is the case, you must determine the proper code for all approach procedures. According to CPT, each may be billed separately, with modifier -51 (multiple procedures) attached.
 
"Multiple surgeons and/or surgeons of various specialties may work together to perform the components of skull-base surgeries, including approaches," Benjamin says. Sometimes, two surgeons from two specialties may perform separate, distinct approaches. For example, the neurosurgeon may perform an infratemporal, preauricular approach to the middle fossa while an otolaryngologist performs a LeFort I osteotomy approach to the anterior fossa. In this case each surgeon may bill separately for his or her approach, with no modifiers attached. Coding is
as follows:
 

Neurosurgeon: 61590
 

Otolaryngologist: 61586.

 
If, however, the surgeons act as co-surgeons, each participating in both approaches, append modifier -62 (two surgeons) to 61586 and 61590 and attach modifier -51 to the lesser-paying code (in this case, 61586, which has 46.39 RVUs versus 73.10 RVUs for 61590):
 

Neurosurgeon: 61590-62 and 61586-62-51
 

Otolaryngologist: 61590-62 and 61586-62-51.

 

"When billing as co-surgeons, each physician must prepare his or her own operative report for all procedures performed," Murtif says.