Introduction

Although there is terrific advancement of endonasal endoscopic procedures, there are still lesions/conditions of the anterior cranial base that require a combined approach. This kind of approach is mainly indicated in case of sinonasal tumors needing a dural resection extending over the orbital roof or with an extensive brain involvement. Thanks to the combined transcranial/transnasal approach and the aid of straight and angled endoscope, this kind of procedure offers a multiperspective visualization of the spaces allowing a more precise dissection and a sound reconstruction.

27.1 Indications

The endoscopic transnasal approach is generally combined to the transbasal (frontal)/subfrontal approach for addressing different pathologies involving the anterior cranial fossa, not amenable for an exclusive endonasal approach.1 The diseases that can be treated by means of such an approach are as follows:

• 
  

  Extensive malignant tumors of the anterior skull base, representing the principal indication for the combined cranio-endoscopic approach. Small- to intermediate -sized sinonasal cancers can be approached through an exclusive endoscopic transnasal transcribriform–transethmoidal approach.2 However, in cases of extensive anterior skull base involvement with massive infiltration of the dura over the orbital roof or brain parenchyma infiltration, detected both in the preoperative or intraoperative settings, the pure endoscopic transnasal approach should be combined with a transcranial frontal/subfrontal approach to obtain a radical resection.1,3

  
  
• 
  

  Benign tumors of the sinonasal compartment with massive frontal sinus involvement or intracranial extension over the orbital roof (e.g., inverted papilloma).

  
  
• 
  

  Inflammatory diseases affecting the frontoethmoidal compartments with osteitis and/or osteomyelitis. In these cases, the diseased bone has to be removed through an extended approach to control the infection and limit the progression of the bony erosion.

  
  
• 
  

  Posttraumatic or spontaneous cerebrospinal fluid (CSF) leaks of the anterior skull base placed in difficult-to-access areas or with an extensive fragmentation of the anterior cranial fossa. In these cases, the exclusive endonasal approach may be difficult and ineffective.

27.2 Surgical Steps

The endonasal transcribriform–transethmoidal and the subfrontal/transbasal approaches can be combined and performed simultaneously by two different surgical teams (neurosurgeons and otorhinolaryngologists), working together through the two corridors (multiportal combined transnasal and transcranial endoscopic-assisted surgery). The transcranial approach improves the control of the supraorbital region and allows a better manipulation of critical structures of anterior cranial base. The transnasal technique allows more precise dissection of the sphenoethmoidal complex with a better management of the sinonasal region.3 Moreover, at the end of the procedure, the endonasal view is especially useful for completing the skull base reconstruction. Indeed, the endoscope makes it possible to verify the watertight closure and to apply eventually fascia in an overlay fashion, for buttressing the anterior skull base reconstruction. The main surgical steps comprised in such an approach are summarized below.

27.2.1 Subtotal Septectomy

Removal of the posterior two-thirds of the nasal septum is performed to gain better exposure of the surgical field and to optimize the endonasal maneuverability of the dedicated instruments, using the two-nostril four-hand technique. The posterior septum is disarticulated from the rostrum of the sphenoid bone, which is then removed to create a bilateral opening in the sphenoid sinus that represents the posteroinferior margin of the dissection. The septal branches of sphenopalatine arteries are isolated and coagulated to reduce bleeding and improve visibility ( Fig. 27.1 ).

27.2.2 Identification of the First Olfactory Fiber

The first olfactory fiber is identified in the olfactory region by means of a careful subperiosteal dissection. This is done to define the starting point of the anterior cranial fossa from an endoscopic endonasal perspective; this step is very useful to perform safely a frontal sinusotomy according to Draf type III. It should be noted that the frontal sinusotomy can be performed also with a lateral to medial direction (this could be advisable in case of difficulties in identifying the first olfactory fiber). This step, absolutely mandatory in exclusively transnasal procedures, could be unnecessary when the frontal sinuses are approached with an additional transcranial opening ( Fig. 27.2 ).

27.2.3 Frontal Sinusotomy (Draf Type III Procedure)

The frontal sinusotomy (see Chapter 4 for detailed description) represents the anterosuperior margin of the dissection, allowing a precise control of the lesion to be treated and its relationship with the anterior cranial fossa. The Draf III median drainage consists in the removal of the frontal sinus floor bilaterally together with the intersinus septum. And as said, the Draf type III procedure can be performed using a medial to lateral or a lateral to medial technique. As mentioned before, endonasal frontal sinusotomy can be unnecessary given the superior—transcranial—control of the frontal sinuses ( Fig. 27.3 ).

27.2.4 Centripetal Resection of Ethmoidal Box

Once the posteroinferior and anterosuperior margins of the resection are exposed, a subperiosteal dissection of the naso-ethmoidal complexes is performed to delineate the lateral borders of the area to be removed. The lamina papyracea should be included in the dissection when the lesion to treat frankly involved it. When required by the extension of disease, endoscopic medial maxillectomy can be performed, to achieve good control of the whole maxillary sinus. This surgical phase has to be associated with nasolacrimal duct exposure and resection, just below the lacrimal sac. In very selected cases, the periorbita and extraconal fat can be removed, if a very limited involvement of these structures is present ( Fig. 27.4 ).4

27.2.5 Completion of Centripetal Resection

Superiorly, the dissection is completed, usually with an anteroposterior direction, by resecting the olfactory mucosa and the basal lamella of the ethmoidal turbinates, to resect the ethmoidal complexes in a centripetal way. Obviously when doing this step, all the olfactory fibers are cut. The naso-ethmoidal complexes are isolated and pushed toward the central part of the nasal fossa (centripetal technique) to extract them through the nasal vestibule or through the oral cavity4 ( Fig. 27.5 ).

27.2.6 Anterior Cranial Fossa Exposure

The ethmoidal roof should be completely exposed with removal of bony partitions by using a drill with a diamond burr. During this step, the anterior and posterior ethmoidal arteries are exposed, cauterized with bipolar electric forceps and cut. The posterior limit of this surgical approach is usually represented by the planum sphenoidale ( Fig. 27.6 ).

27.2.7 Crista Galli Removal

Once the bony anterior skull base is removed (at least at the level of the cribriform plate) and the dural layer is exposed, the crista galli is carefully detached from the dura of the falx cerebri and removed with blunted instruments, trying to avoid dural iatrogenic lesions. In case of wide crista galli, an internal debulking with a diamond burr can be advisable. In approximately 10% of cases, the crista galli is pneumatized. This step can be performed either transnsally or transcranially, according to the preference and experience of the surgical team ( Fig. 27.7 ).

Related posts:

Chapter 30 Anterior Transpetrosal Approach versus EEA Transclival Approach Chapter 28 Retrosigmoid–Transclival Approach Chapter 29 Far Lateral-Craniovertebral Approach Chapter 6 Medial Maxillectomy Chapter 19 Pituitary Gland Transposition and Retrosellar Approach Chapter 16 The Anteromedial Corridor via the Expanded Endonasal Approach: The “Front Door to Meckel′s Cave”

Stay updated, free articles. Join our Telegram channel

Join