Craniofacial Resection
Open Skull Base Surgery
Craniofacial Resection
The combined craniofacial approach to manage tumours involving the anterior skull base has gradually evolved over the past five decades into a safe and reliable technique. It can be extended to resect tumours involving the infratemporal fossa, middle cranial fossa and cavernous sinus.
Indications:
Fig.1
The tumours most commonly requiring combined anterior craniofacial surgery usually begin in the nose or sinuses (Fig.1). Both malignant and benign tumours occur in this region. Tumours with a primary intracranial origin such as meningioma, chordoma or chondrosarcoma require combined resection when they clearly violate the anterior fossa floor.
Surgical Technique:
General anesthesia should be performed by a team experienced in neurosurgical procedures. A lumbar drain is routinely placed and patients are given prophylactic peroperative antibiotic. The patient is then placed in a Mayfield head holder and positioned to optimize both the neurosurgical and facial approaches. The leg is prepped to obtain a skin graft and fascia lata if needed.
The anterior craniofacial approach incorporates a combination of transfacial and transcranial procedures. The facial approach consists of a graduated greater exposure depending on the extent of disease. The basic is done through a lateral rhinotomy approach (Fig.2) coupled with a low craniotomy. The lateral rhinotomy incision may be extended into a Weber-Ferguson incision if a more extensive maxillary excision is required.
Fig.2
Craniotomy:
Fig.3
The craniotomy is tailored according to the extent of involvement of the anterior fossa floor and the degree of dural or frontal lobe invasion. A bicoronal scalp incision (Fig.3) is made running 2 to 3 cms behind the hairline. The flap is elevated in the subgaleal plane down to the eyebrows, then to the lateral orbital walls laterally and just below the nasal glabella medially.
Fig.4
A large flap of pericranial tissue (Fig.4) is created that will be used for later reconstruction. As the dissection proceeds the brows, the supratrochlear and supraorbital neurovascular bundles are exposed and preserved.
The anterior cranial fossa is then exposed by removing a segment of bone, which may be pedicled on the temporalis muscle or completely separated (fig.5a &b). The lower horizontal bone cut should be kept low to lessen the need for subsequent brain retraction. Withdrawing 25 to 50 ml of CSF from the lumbar subarachnoid catheter, lowering pCO2 through controlled hyperventilation, and occasionally administering mannitol or steroids further reduce the need for mechanical frontal lobe retraction. The dura is then carefully dissected off the crista galli and cribriform plate dividing the dural sleeves that extend along the olfactory nerves. The intracranial portion of the tumour extension is then assessed. If it involves the dura or in certain situations, frontal lobe this will have to be resected, together with the tumour. If the dura is intact, it is retracted back to the planum sphenoidale.
Fig.5a
Fig.5b
Facial Approach:
Fig.6
The facial approach depends on the extent of the tumour. Often utilizes modifications of a lateral rhinotomy incision (Fig.6) which may or may not transect the upper lip. This depends on whether a total maxillectomy is done in conjunction with the resection. The periosteum is elevated from the nasal bone as well as from the medial and inferior surfaces of the orbit. The nasolacrimal duct is identified and transected distally. The anterior and posterior ethmoidal arteries are then identified and cauterized or clipped.
In most cases it is necessary to perform a complete enbloc ethmoidectomy. For this purpose a contra lateral lynch incision is made to elevate the contra lateral periorbita, cauterize the anterior and posterior ethmoidal vessels, and make the appropriate osteotomies. If preoperative imaging studies confirm the presence of tumour in the soft tissues of the orbit, then extending the incision laterally to include a portion of the eyelids may facilitate orbital exenteration.
Fig.7
Once the exposure is completed, necessary bone cuts are made with a chisel or saw from above and below to encompass the tumour and the specimen is delivered leaving a large skull base defect (Fig.7).
In most cases it is necessary to perform a complete enbloc ethmoidectomy. For this purpose a contra lateral lynch incision is made to elevate the contra lateral periorbita, cauterize the anterior and posterior ethmoidal vessels, and make the appropriate osteotomies. If preoperative imaging studies confirm the presence of tumour in the soft tissues of the orbit, then extending the incision laterally to include a portion of the eyelids may facilitate orbital exenteration.
Reconstruction:
The secret of avoidance of post operative complications in anterior skull base surgery is the water tight dural closure. If a portion of the dura has been excised, it is repaired with fascia lata.
The pericranium is used for anterior cranial fossa reconstruction. It is usually pedicled on the supraorbital and supratrochlear arteries. The pericranial flap is placed across the defect in anterior cranial fossa. The distal end is placed between the cranial floor bone and the overlying dura. It may be secured with sutures through the bone or anchored with fibrin glue. Unless a large amount of anterior cranial fossa bone has been resected and concern for brain herniation exists, it is usually not necessary to place a bone graft across the bony defect.
Once the pericranial flap is in place the spinal drain is clamped. This will allow gradual reexpansion of the brain to make contact with the pericranial flap, obliterating any residual dead space. Since the pericranial flap traverses the frontal sinus, it is necessary to obliterate the frontal sinus with fat or free muscle after removing all the mucosa in the sinus. If the sinus is quite large, it may be advisable to remove the posterior wall of the sinus completely and allow the brain and dura to expand and fill the space (Cranialization of the frontal sinus)
Fig.8
The bifrontal craniotomy bone flap is then replaced and secured with mini plates. In all cases, nasal pack is placed for at least 5 days post operatively and a lumbar drain kept for the same duration. In significantly larger defects, particularly if orbital exenteration and facial skin is excised, a bulky free flap is considered.
Placing the bicoronal incision behind the hairline and facial incision as described earlier, results in cosmetically acceptable and almost invisible scars (Fig.8).
The Heart Of Clinic
Dr. C. Rayappa MBBS, DLO, FRCS(Edin)
SENIOR CONSULTANT
+91 44 3315 1105
Dr. C. Rayappa graduated from Madras Medical College, Chennai, India in 1982. He completed his post graduation in Otolaryngology (ENT)
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The Heart Of Clinic
Dr. C. Rayappa MBBS, DLO, FRCS(Edin)
SENIOR CONSULTANT
+91 44 3315 1105
Dr. C. Rayappa graduated from Madras Medical College, Chennai, India in 1982. He completed his post graduation in Otolaryngology (ENT)