Microscopic Versus Endoscopic Approaches for Craniopharyngiomas

Choosing the Optimal Surgical Corridor for Maximizing Extent of Resection and Complication Avoidance Using a Personalized, Tailored Approach

James K. Liu, MD; Ilesha A. Sevak, BA; Peter W. Carmel, MD; Jean Anderson Eloy, MD

Disclosures

Neurosurg Focus. 2016;41(6):e5 

In This Article

Extended Transsphenoidal Approaches

While the aforementioned open surgical approaches often require some degree of brain retraction to access suprasellar craniopharyngiomas, the extended EEA via the transplanum transtuberculum corridor provides direct midline exposure to intrasellar/subdiaphragmatic, supradiaphragmatic, and retrochiasmatic craniopharyngiomas that extend up into third ventricle without any brain retraction. When performed with the traditional microscopic speculum-based technique (extended transsphenoidal approach), this transnasal approach was primarily used mainly for craniopharyngiomas of intrasellar and subdiaphragmatic origin with expanded sellas.[13,32] However, with advances in endoscopic endonasal skull base surgery and expanded techniques, a pure EEA has gained increased acceptance for removing more extensive craniopharyngiomas associated with a normal-sized sella and suprasellar tumors of supradiaphragmatic origin.[5,6,12,14,22,23,33,35–37,42–48] The pure EEA has a major advantage when removing retrochiasmatic craniopharyngiomas with suprasellar third ventricular extension since it provides direct visualization of the undersurface of the optic nerves, chiasm, and hypothalamus. The prior aforementioned blind spots underneath the optic chiasm encountered with an approach from above (transbasal interhemispheric or pterional/or-bitozygomatic approach) can be well visualized with an EEA from below. Bimanual microdissection techniques can be performed to carefully dissect the tumor away from the optic chiasm, hypothalamus, and vascular perforators with direct visualization of the surgical plane between the tumor and critical structures.[45,48] By avoiding blind manipulation near critical structures in the retrochiasmatic region, the pure EEA has improved our ability to avoid and minimize visual and hypothalamic complications.[36,42] In addition, the working corridor is between the pairs of neurovascular structures (internal carotid artery, posterior communicating artery, oculomotor nerve) instead of between the nerves and arteries (opticocarotid and carotidoculomotor corridors).

The major limitations of this approach are lateral extension into the sylvian fissure and superior extension into the interhemispheric fissure. Even with the aid of angled endoscopes and instrumentation, there is limited maneuverability and inability to perform direct microvascular repair in the event of vessel injury. The higher risk of postoperative CSF leakage with the EEA was a major criticism when the approach was first introduced. However, this risk has significantly decreased to approximately 5% with the advent of multilayered reconstruction techniques using a vascularized pedicled nasoseptal flap.[26,34] In our experience with the nasoseptal flap, our CSF leak rate has been 3.2%.[49]

The endoscopic endonasal approach can also be considered for recurrent craniopharyngiomas that were previously treated via a craniotomy or prior transsphenoidal approach.[9,14] It can also be used in combination with an open transcranial approach for extensive craniopharyngiomas occupying multiple compartments.

Purely Endoscopic Endonasal Transplanum Transtuberculum Approach: Technical Pearls and Clinical Case Correlates

The patient is positioned supine with the head slightly rotated to the right to facilitate easier access for the operating surgeon standing on the right side of the patient. A lumbar drain is placed prior to incision time for later use postoperatively. We use a 2-surgeon, 3- to 4-hand, binostril technique with a neurosurgeon and an otolaryngologist. For transplanum approaches, we prefer to use 30°-angled endoscopy because it gives the surgeon extra viewing around corners with simple rotation of the scope. The scope is placed in the 6 o'clock position in the right nostril so that the viewing angle is upwards toward the suprasellar region. The neurosurgeon can then work bimanually with the suction placed in the 12 o'clock position in the right nostril, and the working instrument (drill, dissector, microscissors, or tumor aspirator) in the left nostril.

A large vascularized pedicled nasoseptal flap is first harvested and rotated posteroinferiorly into the nasopharynx. Care is taken to protect the vascular pedicle arising from the sphenopalatine artery from inadvertent injury until the time of reconstruction. The middle and inferior turbinates are lateralized followed by a wide sphenoidotomy, posterior ethmoidectomy, and posterior septectomy of about 1.5 cm. It is critical to open the sphenoid as widely as possible, removing all sphenoid septations and bony ridges that may obstruct and hinder surgical freedom and instrument maneuverability. A high-speed diamond drill with copious irrigation is used to remove the bone from the planum sphenoidale, tuberculum sellae, and sellar dura using eggshelling technique. The shape of the bone removal at the planum sphenoidale follows the anterolateral direction of the optic nerves and will therefore appear trapezoidal. We also prefer to decompress the medial aspect of the proximal bony optic canal so that there is good control of the proximal internal carotid artery as it exits the distal dural ring in the subarachnoid space. Next, the dura is opened above and below the intercavernous sinus at the level of the planum and sellar dura. The 2 incisions are then connected by coagulating and dividing the superior intercavernous sinus and diaphragma sellae to gain access to the suprasellar cistern.

The craniopharyngioma can be visualized in the retrochiasmatic space beneath the optic chiasm and between the 2 internal carotid arteries. It is critical to identify the superior hypophyseal arteries and to preserve the branches supplying the undersurface of the optic apparatus to avoid postoperative visual worsening. There is typically an arachnoid layer investing these perforators and by working between the tumor capsule and the arachnoid layer, the perforators can be safely mobilized laterally and preserved during tumor removal. For solid craniopharyngiomas, the tumor is internally debulked with a side-cutting tumor aspirator device (NICO Myriad) or ultrasonic aspirator. When decompressing cystic tumors, it is important to maintain some level of cyst turgor so that a surgical "handle" remains to facilitate extracapsular dissection from the surrounding critical neurovascular structures. We recommend using an extraarachnoid dissection technique—that is, dissecting in the plane between the tumor capsule and the tumor arachnoid, instead of between the tumor arachnoid and cisternal arachnoid.[45,51] This keeps the laterally positioned nerves and vessels protected by both layers of arachnoid. In most cases, the membrane of Liliequist is not breached by the tumor and can act as a plane of dissection to peel the tumor safely from the basilar artery complex and P1 perforators. In some cases, the arachnoid can be thickened and adherent due to chronic inflammation, and therefore, sharp dissection is required.

The inferior aspect of the tumor is elevated from the top of the pituitary gland to identify the base of the pituitary stalk, which is characterized by portal vessel striations. We attempt to preserve the pituitary stalk, if possible, especially if the tumor is readily dissectable off of the stalk. If, however, a gross-total resection is possible and there is tumor invading or expanding the stalk, as in Type II transinfundibular type craniopharyngiomas, we prefer to do a low stalk transection just above the pituitary gland to facilitate total removal and place the patient on postoperative hormone replacement therapy. We agree with the opinion of Dr. Oldfield[51] that this strategy may be better for preventing tumor recurrence than leaving residual tumor on an anatomically intact stalk that may not always retain normal pituitary function, regardless. The tumor is generally most adherent at the level of the hypothalamus where meticulous and careful microdissection is performed. Once the tumor is free from all adherences, the tumor is then carefully delivered from the nose. Premature pulling of the tumor without complete dissection from all adherent neurovascular structures can potentially result in a catastrophic injury to a vessel or nerve.

Successful skull base reconstruction of the dural defect using a multilayered closure technique with a vascularized pedicled nasoseptal flap is critical to prevent postoperative CSF leakage. After obtaining hemostasis, a piece of Gelfoam is placed underneath the dural opening as an inlay to slow the pulsations of CSF out the dural defect. Next, a piece of autologous fascia lata is placed as an overlay graft over the dural opening and held in place with a monolayer of Surgicel placed over the fascia. This step is repeated again with a second layer of fascia lata. Lastly, the nasoseptal flap is then rotated into the sphenoid sinus and carefully placed over the skull base dural repair. It is important to position the flap so that direct contact is made on raw bony surfaces surrounding the skull base defect. The bony surface must be devoid of any sinus mucosa as this will increase the risk of flap dehiscence and possibly the delayed formation of mucoceles. Another monolayer of Surgicel is placed over the edges of the flap against the surrounding bone to promote flap adherence. The flap is then bolstered with several layers of gentamicin-soaked Gelfoam pledgets followed by a Merocel expandable nasal tampon, positioned in the sphenoid sinus posterior to the nasal septum. The lumbar drain is opened temporarily during extubation to allow preferential drainage through the lumbar catheter instead of the skull base repair.

Postoperatively, the patient is maintained on antibiotics until the Merocel packing is removed in the office on postoperative Days 10–12. The lumbar drain is kept open at 5–10 ml per hour for about 72 hours after surgery. Care is taken to monitor for signs and symptoms of CSF rhinor-rhea or intracranial hypotension.

Illustrative Case 4: EEA for Pediatric Retrochiasmatic Craniopharyngioma. This 12-year-old boy presented with progressive visual loss, panhypopituitarism, short stature, and obesity due to a large retrochiasmatic craniopharyngioma extending superiorly into the third ventricle (Fig. 11). After careful inspection of the preoperative MRI, it was determined by our team that the tumor would be favorable for removal via a purely endoscopic endonasal transplanum transtuberculum approach. The sphenoid sinus was generous, and the tumor presented itself to the infrachiasmatic space with a reasonable infrachiasmatic working corridor (distance between the optic chiasm and pituitary gland) (Fig. 12, Video 2).

Figure 11.

Illustrative Case 4 imaging. A and B: Preoperative sagittal and coronal postgadolinium T1-weighted MR images showing a pediatric retrochiasmatic craniopharyngioma compressing the optic chiasm. An EEA was performed and gross-total resection was achieved. C and D: Corresponding postoperative MR images showing no evidence of residual tumor with excellent decompression of the optic chiasm.

Figure 12.

Illustrative Case 4 intraoperative photographs obtained during EEA resection of a pediatric retrochiasmatic craniopharyngioma. A: Endoscopic exposure of planum dura (PD), sellar dura (SD), and optic canals (OC) after removal of bone via transplanum transtuberculum corridor. B: Intradural resection of tumor (T) with careful dissection from the optic chiasm (OC) using a bimanual technique. C and D: View of retrochiasmatic space after tumor removal including third ventricle (3V), hypothalamus (H), and mammillary bodies (M). E: View of skull base dural defect with both frontal lobes (F) exposed. F: Skull base reconstruction with nasoseptal flap (NSF) and preservation of its vascular pedicle (VP).

VIDEO 2. Illustrative Case 4. Video clip showing removal of a pediatric retrochiasmatic craniopharyngioma using an endoscopic endonasal transplanum transtuberculum approach. Copyright James K. Liu. Published with permission. Click here to view.

The plane of dissection was maintained between the tumor capsule and the tumor arachnoid. We also kept the integrity of the membrane of Liliequist, which facilitated tumor dissection away from the basilar artery complex. Direct visualization of the undersurface of the optic chiasm and hypothalamus facilitated tumor dissection, which resulted in complete tumor removal. In this case, the tumor had expanded the stalk (Type II transinfundibular craniopharyngioma) so a low-stalk section was performed to release the tumor for complete removal. Postoperatively, the patient had complete restoration of vision and was maintained on hormone replacement therapy. There was no CSF leakage postoperatively, and the patient has been free of tumor recurrence for over 4 years.

Illustrative Case 5: EEA for Recurrent Cystic Craniopharyngioma. This 32-year-old woman presented with a large, cystic recurrent craniopharyngioma causing compression on her remaining functional left optic nerve. She had undergone multiple previous surgeries for a craniopharyngioma that presented during her childhood, including 3 prior frontal craniotomies and one previous microscopic transsphenoidal resection performed by another surgeon. In her prior surgeries, complete removal of the cyst wall was not achieved and only cystic drainage was performed. Her baseline preoperative examination revealed chronic blindness in the right eye and panhypopituitarism. Her preoperative MRI demonstrated a large enhancing cystic craniopharyngioma that expanded the sella (Fig. 13). We felt that the tumor presented itself to the sphenoid sinus and was, therefore, favorable for an endoscopic endonasal approach. The goal was to attempt complete removal of the cyst wall to prevent any further future recurrences and to preserve vision in her remaining left eye.

Figure 13.

Illustrative Case 5 imaging. A–C: Preoperative sagittal (A), coronal (B), and axial (C) postgadolinium T1-weighted MR images showing a recurrent cystic craniopharyngioma. Near-complete extracapsular resection of fibrous cyst wall was achieved via EEA. Small microscopic remnant was adherent to right cavernous sinus wall. D–F: Corresponding postoperative MR images obtained at 3 months' follow-up showing no gross recurrent or residual tumor.

At surgery, the bony sellar floor was opened widely and the cyst wall was entered to drain the intracystic contents (Fig. 14, Video 3).

Figure 14.

Illustrative Case 5 intraoperative photographs obtained during EEA resection of a recurrent cystic craniopharyngioma. This patient had undergone multiple prior craniotomies and transsphenoidal resection and had vision remaining only in the left eye. A: Endoscopic transsphenoidal transsellar exposure of cyst wall (CW). B: Thick and fibrous cyst wall (CW) was fenestrated widely to drain cystic contents. C–E: Extracapsular dissection of cyst wall (CW) away from the left optic nerve (ON) and both walls of the cavernous sinus. F: Final view after near-complete removal of cyst wall. Small microscopic remnant was adherent to the right cavernous sinus wall. The right optic nerve was atrophic and not visible because the patient was chronically blind in the right eye.

VIDEO 3. Illustrative Case 5. Video clip showing extracapsular dissection of recurrent fibrous cystic craniopharyngioma using endoscopic endonasal approach. Copyright James K. Liu. Published with permission. Click here to view.

The cyst wall was noted to be very thick and fibrous. Extracapsular removal of the cyst wall was performed by initially developing a plane of dissection between the left lateral aspect of the cyst wall and the left medial wall of the cavernous sinus. Direct visualization of the wall was facilitated with a 30°-angled endoscope. The tumor was safely dissected from the left optic nerve and chiasm. The right optic nerve was atrophic from chronic blindness and not readily identifiable. The remainder of the cyst wall was debulked with a side-cutting tumor aspirator. A near-total resection was achieved, leaving a microscopic remnant adherent to the right medial wall of the cavernous sinus. Postoperatively, the patient had normal vision in the left eye and no CSF leakage. She underwent fractionated radiation therapy to the right cavernous sinus and has not had any further recurrences at 3 years' follow-up. This case illustrates the importance of complete cyst wall removal and the usefulness of the EEA for recurrent tumors despite prior multiple craniotomies and transnasal procedures.

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