Key points

A video of the endoscopic endonasal resection of an intraventricular craniopharyngeoma accompanies this article at http://www.neurosurgery.theclinics.com/

Introduction

Craniopharyngiomas (CPs) represent one of the most challenging tumor entities in neurosurgery. Because of its critical vicinity to important neurovascular structures, the surgery is demanding and requires a thorough understanding of the anatomy of the suprasellar region.

CPs are benign epithelial tumors of the sellar region originating from remnants of Rathke’s cleft. They are classified by the World Health Organization as grade I neoplasms. The papillary form is almost exclusively found in the adult population and the adamantinomatous subtype mainly occurs in children. There is a bimodal age distribution of the incidence of CPs with a higher amplitude in childhood. However, the prognosis of these tumors in particular is a matter of growth pattern. The extent of the tumor in relation to the optic chiasm, pituitary gland and stalk, hypothalamus, carotid artery, and anterior cerebral artery complex as well as the location of the tumor with respect to the sella and diaphragm, is important for surgical planning. In addition to the tumor size and the multilobulated characteristics with solid and cystic components, it is of significant interest whether the lesion does extend into the third ventricle or not and its relation to it. To solve the problem of choosing the right surgical strategy for individual cases, a variety of topographic and clinical classifications of CPs have been transferred into surgical practice parallel to technological progress of instrumentation and equipment.

Albert E. Halsted has been credited with the first successful transsphenoidal resection of a CP performed in 1909. The transsphenoidal approach for tumors of the sellar region is strongly related to Harvey Cushing and Oskar Hirsch. In 1909, Cushing described his first surgery through the transsphenoidal route for partial removal of the pituitary gland in a patient with acromegaly. A detailed historical review concerning the endonasal approach for CPs written by Gardner and colleagues mentioned that Cushing abandoned the approach for CPs for safety reasons given by technological and visualization limitations. In contrast, Hirsch developed and kept to the endonasal transsphenoidal approach and reported his first small series of 12 patients treated for tumors of the pituitary gland in 1911 at the third international laryngo-rhinological congress in Berlin. Ten of the patients improved in clinical outcome and 2 died. The latter were subjected to autopsy. In one, a large tumor of the pituitary gland was found that mainly extended into the intracranial space and third ventricle. Hirsch made 2 important statements about his experience regarding the transsphenoidal approach. First, an improvement of clinical symptoms can be expected if the tumor is located exclusively inside the sella and reveals cystic components. Second, if a tumor is mainly growing intracranially, the endonasal approach and all other extracranial methods will not succeed. Fortunately, the introduction of the operating microscope opened a new door to neurosurgery in general, as well as to the transsphenoidal endonasal route particularly. Hardy stressed the importance of the microsurgical approach for pituitary adenomas and CPs in 1971 and mentioned that “the intrasellar subdiagphragmatic type of CP can be totally removed transphenoidally.” Laws improved the microsurgical technique for CPs and expressly underlined that if “the sella turcica is enlarged, transsphenoidal microsurgery can be the procedure of choice, even when significant intracranial extension is present.”

The stepwise technological progress extended the transsphenoidal access, initially described by Weiss, to reach the suprasellar/supradiaphragmatic space. However, transcranial approaches to CPs with intraventricular growth have also been used via pterional, transcortical, interhemispheric, transcallosal, and transforaminal routes.

The microsurgical–endonasal resection of sellar tumors was successfully complemented by the use of an endoscope by Apuzzo and colleagues in 1977 after Guiot had already introduced the endoscope to transsphenoidal surgery more than a decade earlier. Two decades later, Carrau and Jho reported their first series of purely endoscopic endonasal removal of pituitary adenomas. The continuous advancement of the endoscope, in addition to the development of specific instruments and sophisticated endoscopic studies of the parasellar and anterior skull base anatomy allowed the extension of the spectrum of indications for the technique. This initial work was spearheaded by “The original Pittsburgh group” with Carrau, Kassam and co-workers as well as the Naples group with Cappabianca and De Divitiis, and also the Bologna group with Frank and Pasquini, who promoted the endoscopic extended endonasal approach in the early years of the 21st century. Nowadays, the endoscopic approach is widely accepted and is used regularly. However, there is a long learning curve and cadaver studies are recommended. Additionally, close cooperation between an ENT-head and neck surgeon and neurosurgeon is necessary. Based on their extraordinary experience, Kassam and colleagues specified a V-level scale of complexity of endoscopic endonasal skull base procedures that provides a useful guide. According to their scale, the endoscopic endonasal approach to CPs is a level IV category referring to the fact that intradural surgery is usually required. Several studies have demonstrated already excellent results for CP patients. Compared with the transcranial microscopic approach, the endoscopic approach promises a higher rate of gross total resection (GTR) and improved visual outcome because there is less manipulation of the optic apparatus, especially in retrochiasmatic lesions.

Introduction

Craniopharyngiomas (CPs) represent one of the most challenging tumor entities in neurosurgery. Because of its critical vicinity to important neurovascular structures, the surgery is demanding and requires a thorough understanding of the anatomy of the suprasellar region.

CPs are benign epithelial tumors of the sellar region originating from remnants of Rathke’s cleft. They are classified by the World Health Organization as grade I neoplasms. The papillary form is almost exclusively found in the adult population and the adamantinomatous subtype mainly occurs in children. There is a bimodal age distribution of the incidence of CPs with a higher amplitude in childhood. However, the prognosis of these tumors in particular is a matter of growth pattern. The extent of the tumor in relation to the optic chiasm, pituitary gland and stalk, hypothalamus, carotid artery, and anterior cerebral artery complex as well as the location of the tumor with respect to the sella and diaphragm, is important for surgical planning. In addition to the tumor size and the multilobulated characteristics with solid and cystic components, it is of significant interest whether the lesion does extend into the third ventricle or not and its relation to it. To solve the problem of choosing the right surgical strategy for individual cases, a variety of topographic and clinical classifications of CPs have been transferred into surgical practice parallel to technological progress of instrumentation and equipment.

Albert E. Halsted has been credited with the first successful transsphenoidal resection of a CP performed in 1909. The transsphenoidal approach for tumors of the sellar region is strongly related to Harvey Cushing and Oskar Hirsch. In 1909, Cushing described his first surgery through the transsphenoidal route for partial removal of the pituitary gland in a patient with acromegaly. A detailed historical review concerning the endonasal approach for CPs written by Gardner and colleagues mentioned that Cushing abandoned the approach for CPs for safety reasons given by technological and visualization limitations. In contrast, Hirsch developed and kept to the endonasal transsphenoidal approach and reported his first small series of 12 patients treated for tumors of the pituitary gland in 1911 at the third international laryngo-rhinological congress in Berlin. Ten of the patients improved in clinical outcome and 2 died. The latter were subjected to autopsy. In one, a large tumor of the pituitary gland was found that mainly extended into the intracranial space and third ventricle. Hirsch made 2 important statements about his experience regarding the transsphenoidal approach. First, an improvement of clinical symptoms can be expected if the tumor is located exclusively inside the sella and reveals cystic components. Second, if a tumor is mainly growing intracranially, the endonasal approach and all other extracranial methods will not succeed. Fortunately, the introduction of the operating microscope opened a new door to neurosurgery in general, as well as to the transsphenoidal endonasal route particularly. Hardy stressed the importance of the microsurgical approach for pituitary adenomas and CPs in 1971 and mentioned that “the intrasellar subdiagphragmatic type of CP can be totally removed transphenoidally.” Laws improved the microsurgical technique for CPs and expressly underlined that if “the sella turcica is enlarged, transsphenoidal microsurgery can be the procedure of choice, even when significant intracranial extension is present.”

The stepwise technological progress extended the transsphenoidal access, initially described by Weiss, to reach the suprasellar/supradiaphragmatic space. However, transcranial approaches to CPs with intraventricular growth have also been used via pterional, transcortical, interhemispheric, transcallosal, and transforaminal routes.

The microsurgical–endonasal resection of sellar tumors was successfully complemented by the use of an endoscope by Apuzzo and colleagues in 1977 after Guiot had already introduced the endoscope to transsphenoidal surgery more than a decade earlier. Two decades later, Carrau and Jho reported their first series of purely endoscopic endonasal removal of pituitary adenomas. The continuous advancement of the endoscope, in addition to the development of specific instruments and sophisticated endoscopic studies of the parasellar and anterior skull base anatomy allowed the extension of the spectrum of indications for the technique. This initial work was spearheaded by “The original Pittsburgh group” with Carrau, Kassam and co-workers as well as the Naples group with Cappabianca and De Divitiis, and also the Bologna group with Frank and Pasquini, who promoted the endoscopic extended endonasal approach in the early years of the 21st century. Nowadays, the endoscopic approach is widely accepted and is used regularly. However, there is a long learning curve and cadaver studies are recommended. Additionally, close cooperation between an ENT-head and neck surgeon and neurosurgeon is necessary. Based on their extraordinary experience, Kassam and colleagues specified a V-level scale of complexity of endoscopic endonasal skull base procedures that provides a useful guide. According to their scale, the endoscopic endonasal approach to CPs is a level IV category referring to the fact that intradural surgery is usually required. Several studies have demonstrated already excellent results for CP patients. Compared with the transcranial microscopic approach, the endoscopic approach promises a higher rate of gross total resection (GTR) and improved visual outcome because there is less manipulation of the optic apparatus, especially in retrochiasmatic lesions.

Indications and limitations for endoscopic extended endonasal approach

Patients with CPs can present with a great variety of symptoms including headache, visual symptoms, hormonal disorders such diabetes insipidus and hypopituitarism, mental and memory disturbances, gait difficulties, and hypothalamic disturbances such as the Fröhlich’s syndrome (adiposogenital dystrophy). The typical symptoms of increased intracranial pressure are commonly related to an associated hydrocephalus owing to tumor extension into the third ventricle.

All symptomatic CPs are an indication for surgery. Asymptomatic lesions can be followed with MRI. However, growing lesions should be treated before they become symptomatic. If the patient presents with acute hydrocephalus owing to obstruction of the foramina of Monro by a cystic component of the tumor, an initial transcranial transventricular endoscopic cyst fenestration can be performed before the endonasal tumor resection to release the increased intracranial pressure.

The goal of surgery for CPs is GTR or near total resection, if feasible. However, tumor removal has to be restricted to subtotal resection or even partial resection when the risk of neurovascular damage is expected to be high to avoid unacceptable postoperative morbidity. The surgical approach depends on the individual growth pattern of the tumor. Important essentials for the endoscopic extended endonasal approach are listed in Table 1 and limitations are presented in Box 1 with respect to the recent literature. Categories A through G try to display an increase of the necessary surgical expertise according to certain pathologic conditions. Each surgical case must be assessed individually for the endoscopic extended endonasal approach or should be alternatively considered for a primary or second stage transcranial approach. Type IV CP isolated to the third ventricle and/or optic recess according Kassam and colleagues is stressed to be not feasible by extended endonasal approach. In our opinion, the endonasal approach is especially useful and superior to any transcranial approach when the lesion is retrochiasmatic with a prefixed chiasm. Compared with the transcranial approach, manipulation of the optic apparatus is reduced, as is the risk of visual deterioration. The success of tumor removal depends on the consistency and characteristics of the lesion (solid, cystic, or multilobular) as well as the invasion of the hypothalamic area. The latter has to be thoroughly assessed in all kind of CPs involving the third ventricle and represents the main reason for preventing a GTR.

Surgical management

Preoperative Planning

Taking a case history and performing a neurologic examination are the first steps in the patient evaluation. Additionally, endocrinologic and visual assessment (visual acuity and visual field) is mandatory before and after surgery. An early consultation with an ENT is advisable to define details of the individual surgical strategy. We strongly recommend neuropsychological testing for adults and children before surgery, if the condition of the patient allows, because behavioral or cognitive problems can already be present before intervention or might occur after tumor resection. Furthermore, the body mass index and eating behavior are of interest because of the possibility of postoperative obesity and hyperphagia owing to hypothalamic damage.

Sophisticated preoperative imaging is of utmost importance and includes CT and MRI. CT reveals calcifications within solid nodules and rim or capsule of cystic parts. Thin layer bone window CT demonstrates the bony anatomy of the paranasal sinuses, nasal cavity, clivus, and anterior skull base. It discloses nasal septum deviations, conchal abnormalities, and provides an exact map of the intrasphenoid septations, which are important for anatomic orientation. MRI demonstrates tumor extension in every plane including differentiation in solid and cystic components of the tumor. It provides the basis to evaluate the surgical corridor as mentioned in Table 1 and Box 1 . Neurovascular conflicts such as distortions of the optic chiasm or branches of the Circle of Willis are well visualized on T2 sequences. These authors agree with others that a special meaning is related to the axial and coronal fluid-attenuated inversion recovery or T2 sequences regarding hypothalamic invasion by the tumor. Our illustrative case presents typical MRI features ( Fig. 1 ).

This 61-year-old man presented with a 6-month history of progressive mental deterioration including decrease of short-term memory. Ten days before admission, he developed a disturbance of consciousness, disorientation, and bladder dysfunction. Endocrinologic evaluation demonstrated panhypopituitarism and diabetes insipidus. A typical Addisonian crisis was observed. MRI revealed a suprasellar contrast enhancing tumor extending into the third ventricle with solid components ( A ). The optic chiasm was displaced anteriorly ( arrow ). Pituitary gland and sella seemed to be normal. Hypothalamic invasion of the lesion was suspected because of the perifocal edema on T2 and fluid-attenuated inversion recovery images with lateral extension into the basal ganglia on the right side ( B ). Gross total resection was performed, including section of the pituitary stalk, which was already infiltrated and destroyed by the tumor. The sphenoid and intradural phases of the extended endonasal approach is shown in Figs. 2 and 3 . Postoperatively, the patient was very confused, but recovered soon regarding conscious level and cognitive function. Surprisingly, body weight remained stable. Hormonal substitution is required. There is no recurrence of the tumor on MRI 2 years after surgery ( C, D ). The edema has resolved completely ( C ). Image ( D ) also demonstrates covering of the skull base defect by the nasoseptal flap.

Depending on the imaging findings, an approach is selected. The decision to approach the lesion transcranially or endonasally depends on several factors. One of the most important considerations is the position of the chiasm in relation to the tumor. If the tumor is located retrochiasmatic, pushing the chiasm anteriorly (prefixed chiasm), the endonasal approach provides better access to the lesion avoiding unnecessary manipulations of the chiasm. This is especially true in smaller tumors, which only elevate the floor of the third ventricle but are not located intraventricularly. In these lesions, the lamina terminalis approach should not be chosen. If the tumor is located anteriorly to the chiasm causing a postfixed chiasm like in tuberculum sellae meningiomas, the lesion can be approached transcranially or endonasally. However, in most CPs, there is a prefixed chiasm. If the tumor has significant lateral extension (>1 cm lateral to the carotids), it might be impossible to remove these parts totally through the nose when they are stuck to the surrounding structures. Tumors with large lateral extension should undergo removal via craniotomy. However, tumor extension into the third ventricle, even when they fill the entire ventricle, can be removed endonasally, provided there is communication with the suprasellar space and no ventricular wall invasion. The axis of the approach is ideal to get even the tumor parts in the posterior third ventricle.

Usually, a transsellar–transtuberculum–transplanum approach is sufficient to remove a CP. In tumors with retroclival tumor extension, an addition transclival approach has to be added. In giant tumors with extension in all directions, a combined endonasal–transcranial approach may be necessary. In the rare instance of a purely intrasellar craniopharyngeoma, a simple transsellar approach is sufficient. The approach, steps, and goal of the surgery should be discussed between rhinosurgeon and neurosurgeon at least the day before the surgery.