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Surgical Treatment of Craniopharyngiomas


Preoperative Considerations

  • Craniopharyngiomas are tumors with solid-cystic components that originate from embryological remnants of the Rathke's pouch. They represent 1–3% of lifetime intracranial tumors and up to 5–10% occurring during childhood.

  • They are commonly located in the suprasellar region, arising from the pituitary stalk and adjacent to the optic chiasm but they can be found anywhere in the sella and suprasellar space following the embryologic migration pathway of the Rathke's pouch ( Figure 25.1 ). Histologically, these tumors are divided in two groups: adamantinomatous, which is the most common type found during childhood; and papillary, seen almost exclusively in the adult patient group.

    Figure 25.1, Classification of craniopharyngiomas based on their anatomic location in relation to the pituitary stalk (PS). (A) Type I represents a preinfundibular lesion where the tumor is completely located in front of the PS. (B) Type II is a transinfundibular craniopharyngioma arising within the PS. (C) Type III is a retroinfundibular lesion. This tumor extends beyond the PS and can protrude into the third ventricle. Types I and II are usually good candidates for endoscopic resection whereas type III craniopharyngiomas usually benefit from transcranial resections.

  • Symptoms may present depending upon the precise location of the tumor and its relationship to adjacent normal structures. Common symptoms include visual deficits secondary to compression of the optic chiasm, endocrine abnormalities and headaches.

  • Preoperative work-up must include:

    • Neuroimaging (MRI and CT scan): useful for evaluation of the location of the tumor and its relation to the sella, optic chiasm, third ventricle, cavernous sinus and internal carotid artery.

    • Neuro-ophthalmological evaluation and visual field testing.

    • ENT evaluation and face CT scan for analysis of the nasal cavity and sinus anatomy.

    • Endocrinological evaluation.

Indications

  • Treatment modalities include conservative treatment, surgery and radiotherapy.

  • Conservative treatment is considered for small asymptomatic lesions. In these cases, close radiological follow-up with MRI scans and routine endocrinological evaluation are recommended.

  • Radiotherapy is a treatment option in the management of recurrent and residual lesions, especially those who are not closely related to the optic chiasm. Radiosurgery and stereotactic fractionated radiotherapy are usually employed in such cases. Complications potentially associated with this treatment include radiation necrosis, optic neuritis, endocrine deficits and dementia.

  • Surgery is considered in cases that present with:

    • Progressive enlargement of the lesion.

    • Development of neurological signs and/or intracranial hypertension.

    • Endocrine abnormalities.

  • Transcranial and transsphenoidal approaches are useful for the resection of those lesions.

  • The transsphenoidal approach is especially useful in the following cases:

    • Small and medium-sized lesions located at the midline, without invasion of neurovascular structures.

    • Sellar craniopharyngiomas.

    • Suprasellar lesions without significant lateral extension.

  • Currently, transcranial approaches are recommended in the following cases:

    • Large suprasellar lesions with important lateral extensions toward the deep part of the sylvian fissure, with encasement of the middle cerebral artery and lenticulostriate branches.

    • Large lesions with peritumoral brain edema.

    • Invasion of brain parenchyma.

  • Different transcranial approaches can be performed to remove those lesions, including the pterional, supraorbital and orbitozygomatic (OZ) approaches.

    • The OZ technique is adequate for most craniopharyngiomas that require transcranial approaches. The removal of the orbital rim and roof allows exposure of the suprasellar region with minimal retraction of the frontal lobe, allowing adequate visualization of the tumor and its surroundings during microsurgical resection.

  • The main objective in the surgical treatment of craniopharyngiomas is to obtain gross total resection of the tumor while preserving the endocrine and visual functions of the patient.

  • In order to preserve those functions, partial resection may be considered in those lesions closely adherent to the optic apparatus, hypothalamus and/or internal carotid branches. In those cases, postoperative follow-up with MRI scans or adjuvant radiotherapy are useful options.

Surgical Procedure: Endoscopic-Assisted Transsphenoidal Technique

Patient Positioning

  • The patient is placed in a horseshoe or a 3-point head fixation system (Mayfield skull clamp or similar) in a slightly extended position to angle the planum sphenoidale, tuberculum sella and sphenoidal sinus rostrally. Additionally, the head is rotated 5–10° towards the surgeon so the nasal cavity is parallel to the surgeon's working angle.

  • The perinasal skin and nasal cavity are prepared with povidone iodine.

  • A small skin area is prepped at the abdomen or waist, for removal of a fat graft or fascia lata that may be used to reconstruct the sellar floor at the end of the procedure.

  • After adequate prepping and draping, the nasal cavity is packed for approximately 2 minutes with afrin-soaked pledgets to reduce the bleeding originated by nasal mucosa manipulation.

Endonasal Phase

  • A 0° degree endoscope is placed at the upper part of the right nostril; visualization of the inferior and middle nasal turbinate is essential for guidance in the initial part of the procedure. The choice of operative side can also be made depending on the side that offers more space and access.

  • Once the inferior and middle turbinates and the nasal septum are identified, a vasoconstrictor solution composed by 0.25% lidocaine and epinephrine (1: 200 000) is injected submucosally, in order to reduce the mucosal bleeding during manipulation of these structures and to reduce postoperative pain.

  • With a Penfield No. 2 dissector, lateralization of the ipsilateral middle turbinate is performed to enlarge the working space in the nasal cavity. For midline approaches, resection of the middle turbinates is avoided. This may help in preventing olfactory function damage and postoperative empty nose syndrome.

  • The sphenoid ostium is localized approximately 1 cm superior and medial to the middle turbinate.

  • If the tumor resection is done with the microscope instead of the endoscope, a nasal speculum is inserted at this point, to maintain an adequate surgical field between the turbinates and the nasal septum. The speculum is gently placed in the right nostril, between the turbinates at the lateral wall of the nasal cavity, and the nasal septum at the midline. The speculum must be opened carefully in order to avoid excessive pressure over the nasal structures. The blades of the speculum will retract laterally the mucosa that covers the rostrum sphenoidale.

  • The opening of the sphenoid sinus can be started widening the sphenoid ostium with a Kerrison punch. The bone dissection is directed inferiorly and medially. At this point, the posterior part of the nasal septum is dislocated by pushing it towards the contralateral side with the use of a Penfield No. 2 dissector or breaking it with the Kerrison inserted inside the space provided by the widened ostium. This detaches the posterior attachment of the nasal septum to the rostrum giving complete access to the sphenoid sinus. With a high-speed drill, 1–2 cm of the posterior edge can be resected for enlargement of the surgical view according to the size and location of the lesion.

  • Wide bilateral opening of the bony limits of the sphenoid sinus can be then performed with use of a high-speed drill and micro-rongeurs. Preservation of the inferior portion of the vomer, an important midline anatomic landmark to guide the surgeon throughout the approach, is recommended.

  • The mucosa inside the sphenoid sinus is removed with blunt endoscopic forceps. The septations inside the sphenoid sinus are removed with a drill or rongeur in order to expose the anterior wall of the sella. It is not unusual that the septations deviate towards the internal carotid arteries; in this case, the septations may be removed with extreme care to avoid an injury.

  • Once inside the sphenoid sinus, the surgeon identifies the sella, carotid protuberances, tuberculum sphenoidale, planum sphenoidale and posterior portion of the cribriform plate. Although it is not necessary to depend on neuronavigation, neuronavigation guidance can be used for identification of these structures ( Figure 25.2 ).

    Figure 25.2, Endoscopic endonasal view demonstrating the anatomy of the region. (A) The posterior part of the nasal septum and the ostium sphenoidale is shown (arrows). mt, middle turbinate. (B) It is possible to appreciate the sella (S), superiorly the planum sphenoidale (PS) and the optic nerves (O), the lateral walls of the cavernous sinus (CS), the internal carotid artery (C) and the clivus, inferiorly (Cl).

  • Under microscopic guidance, the sellar floor is removed with the use of a high-speed drill or a Kerrison punch. A bayonet dissector can be introduced in the initial aperture to create a plane in between the sellar floor and the dura mater. For a standard transsphenoidal approach, the sellar floor drilling is extended laterally up to the level of the carotid prominences, superiorly up to the tuberculum and inferiorly until the junction of the clivus with the sellar floor.

  • Craniopharyngiomas with an extensive suprasellar component may require expanded approaches, with drilling of the sellar floor, tuberculum and planum sphenoidale. In those cases, a vascularized nasoseptal flap can be prepared at the beginning of the procedure to be used during reconstruction of the skull base floor.

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