Treatment of Craniopharyngioma: Transcranial Approach
This was a case of a 7-year-old boy. The tumor cyst expands to the mid-lower portion of the clivus. The operation uses a lateral fissure transtentorial approach. The posterior fossa tumor is fully exposed through the cerebellar hiatus. The schematic diagrams in the black box in the upper right corner show that the bone window is enlarged backwards to expose the posterior tumor part (gray shadow in the pictures). (a) Intraoperative picture showed the anatomy around right side of the cerebellar hiatus; (b, c) pre- and postoperative MR sagittal images. (1) Right-side ICA, (2) optic chiasm, (3) right-side oculomotor nerve, (4) tentorial margin, (5) basal artery, (6) tumor exposed through the cerebellar hiatus
6.3.2 The Midline Approaches
The midline approach mainly includes the frontobasal anterior interhemispheric approach and the interhemispheric transcallosal approach. Some scholars advocate the removal of the craniopharyngioma that invades the third ventricle through the transcallosal approach. However, the authors believe that this approach is difficult to dissect the tumor at the original site of infundibular tuberculum, so it is not described in this atlas.
The following focuses on the surgical techniques in the frontobasal anterior interhemispheric approach:
When the frontobasal anterior interhemispheric approach is used, the exposure of the tumor is mainly through two major surgical spaces: the prechiasmatic space and the lamina terminal space.
In this chapter, we mainly discuss two major surgical techniques in frontobasal anterior interhemispheric approach: (1) drilling of tuberculum bone to increase prechiasmatic space and intrasellar tumor exposure; (2) detachment of anterior communicating artery to increase space at the lamina terminal.
6.3.3 Increase Intrasellar Tumor Exposure by Drilling Bone at the Tuberculum Sellae
The prechiasmatic space is sometimes narrow in craniopharyngioma. Some patients belong to prefixed optic chiasm (the short optic nerve, anatomical variation), and more patients are due to the retrochiasmatic tumor (type T tumors). Drilling the bones of the tuberculum sellae and the sphenoidal platform can increase the space for surgical manipulation and reduce the traction on the optic chiasm. More importantly, through bone removal, the intrasellar tumor can be exposed under direct vision. It is particularly meaningful for the removal of type Q tumor (subdiaphragmatic CP), which can improve the total resection rate and of the possibility of pituitary stalk preservation (Fig. 6.2).
6.3.4 Division of the Anterior Communicating Artery to Exposure of Cistern at the Lamina Terminal
Lamina terminal space is the main corridor for T-type craniopharyngioma through the anterior interhemispheric approach. The lamina terminal is often crowded by the blood vessels of the anterior communicating artery complex. Therefore, dividing of AcoA becomes the choice. Dividing of the artery will provide adequate exposure of the lamina terminal space, making the surgical manipulation more convenient and safer (Fig. 6.3).
Because of the difference in anatomical development, the vascular architecture of the anterior communicating artery complex is diverse (Fig. 6.4). Therefore, it is important to evaluate the vascular structure of the anterior communicating artery before and during the operation for the division of the artery.
The evaluation methods mainly include: (1) preoperative angiography to understand the development of bilateral A1 and A2 segments and the morphology of the anterior communicating artery; (2) intraoperative microscopic exploration of the development of bilateral anterior cerebral arteries; (3) intraoperative experimental blockade using temporary aneurysm clip, and the blood supply of bilateral A2 segments and the perforating vessels were observed. If necessary, intraoperative phthalocyanine green angiography is a useful method (Figs. 6.5 and 6.6). It is worth emphasizing that dividing of anterior communicating artery is not a necessary step in the treatment of T-type craniopharyngioma through the trans-laminal terminal approach. In addition to assessing its feasibility, the growth characteristics of the tumor itself are more important factor. In the authors experience, only those cases where the tumor is located in a high position in the direction of the third ventricle (for example, 2/3 of the tumor exceeds the anterior communicating artery complex, the tumor significantly exceeds the anterior commissure, etc.) are the potential indication of the artery division.
6.4 Illustrate Cases
Here, we will discuss three types of tumors (type QST), which were removed using transcranial approaches; the surgical procedures and techniques for each type of tumor will be described and illustrated.
6.4.1 Type Q
22.214.171.124 Case 1
This was the case of a 9-year-old girl with a 12-month history of headache and decreased vision for 1 month. Her height was 115 cm, which is lower than average for her age and sex by 2 SD, and she was under the third percentile of average height for Chinese girls. Endocrinological examination revealed hypo-thyroxine and growth hormone axis and increased levels of prolactin (31 ng/μL).
Analysis Before Surgery
The tumor was a typical type Q tumor, and the patient’s primary complaint was vision disturbance, and she presented with growth retardation.
Surgical consideration: Type Q tumor growth began below the diaphragm and arachnoid. The suprasellar part was covered by the diaphragma sellae (DS) and arachnoid above the DS, and therefore this kind of tumor is considered the optimal tumor type for the transsphenoidal approach. However, there are several difficulties associated with selection of the transsphenoidal approach for the management of this type Q tumor (Fig. 6.7).
The suprasellar part of the tumor breaks through the diaphragma sellae into the anterior cranial fossa, which might present a significant challenge to GTR.
The PS always inflates and fuses with the tumoral cystic walls. The absence or interruption of the PS is very often associated with posterior pituitary gland anomalies and hormonal dysfunction. As a result, these tumors are difficult to treat surgically with the transsphenoidal approach with preservation of the PS and pituitary function.
The midline interhemispheric approach was selected for gross total or maximum possible safe resection and to maintain the intactness of normal nervous tissues, especially the infundibulum-pituitary stalk tract. The ultimate goal of surgery is to pursue a certain quality of life while removing the tumor, specifically the endocrine function dominated by the hypothalamic-hypophyseal axis.
The operative steps involving craniotomy utilized for the removal of type Q craniopharyngiomas can be summarized as follows: (1) standardized skull base craniotomy (frontobasal interhemispheric craniotomy), (2) separation of the tumor from suprasellar structures and the stretched, attenuating DS, (3) resection of the bone at the tuberculum sellae to provide direct vision on the intrasellar tumor portion, (4) T-shaped incision of the elevated DS, and (5) tumor dissection along the true capsule while attempting to preserve the neurohypophysis and continuity of the PS.
Postoperative MRI (10a–c) obtained after 24 months revealed total tumor removal with preservation of the pituitary stalk (Fig. 6.16). Endocrinological detection performed 6 months after surgery indicated no new hormone deficiencies. The PRL level was normal, although the levels of several sexual hormones remained low.
The patient’s visual symptoms had recovered by the time of the last official follow-up, which was conducted at 24 months postoperatively. Her diabetes insipidus (DI) recovered gradually. She was able to attend school and did not require hormone replacement therapy at the time of the last follow-up study.
126.96.36.199 Case 2
This was the case of a 6-year-old male patient with a 12-month history of intermittent headache and vomiting. He also exhibited growth failure, emaciation, and partial hypopituitarism. He presented with visual deterioration (right eye: 0.4, left eye: 0.08) and bitemporal hemianopia.
Physical and Experimental Examination
The patient’s routine blood and urine analysis results were normal; however, he had low levels of plasma thyroxine and free thyroxine (fT4). An insulin stimulation test for cortisol and growth hormone (GH) revealed subnormal responses.
Radiological Images Before Surgery
A predominantly cystic intra- and suprasellar mass was identified both on CT and MRI (Fig. 6.17). The anterior communicating (AcoA) and anterior carotid arteries (ACA) formed a snowman shape at the top of the cystic tumor. On enhanced MRI, the cystic tumor wall was significantly enhanced roundly. On a coronal scan, a solid tumor was observed on the right side of the pituitary fossa near the medial wall of the CS. No obstructive hydrocephalus consequent to the tumor growth pattern and expansion was observed.
Analysis Before Surgery
Surgical and topographic tumor classification: Type Q tumor (intra- and suprasellar Id-CP).
Relationship with the AcoA: The AcoA complex was displaced upwards.
Tumor growth began below the diaphragm and arachnoid. The suprasellar part was covered by the diaphragma sellae and arachnoid above the DS.
Surgical excision should be the first-line therapy. A frontobasal interhemispheric approach was ultimately selected to reach the lesion.
After general anesthesia induction, the patient was placed in the supine position with the head fixed in a Mayfield three-pin head-holder. The head was extended slightly downward (approximately 15°), allowing the frontal lobe to spontaneously fall downward because of gravity during surgery. A standard frontobasal interhemispheric craniotomy (FIH) was performed (Fig. 6.18). A square of forehead periosteum was maintained for further frontal sinus repair. The bone flap extended beyond the median line, with the lowest margin as near as possible to the nasion. The mucosa inside the frontal sinus was removed carefully after opening the bone window. The bone of the posterior sinus wall was removed and drilled to increase exposure. Next, bone wax with antibiotic powder was used to fill the sinus cavity completely and reduce the risk of intracranial infection. A curved incision was made to open the bilateral dura mater beside the superior sagittal sinus; this incision was made close to the skull base. Subsequently, the anterior part of the superior sagittal sinus was ligated, followed by removal of the cerebral falx. The dural flap was turned rearward.
Dissection of the Interhemispheric Fissure
A self-retaining retractor was used to retract the bilateral frontal lobe. The bilateral frontal lobes were separated along the interhemispheric corridor and the cerebrospinal fluid (CSF) was drained to the extent possible. Occasionally, dissection of the frontal interhemispheric fissure is much more complex than that used in a lateral transsylvian approach, especially in patients with increased intracranial pressure (ICP). Continuous lumbar CSF drainage during dissection is a valid method of ICP release. The planum sphenoidale, optic chiasm, and cisterna lamina terminalis were exposed in a stepwise fashion after allowing the frontal lobe to fall.
The enlarged prechiasmatic space was the major corridor for surgical manipulation. Because of diaphragmatic septation, the suprasellar cystic tumor could be separated via slight pulling from the circle of Willis vascular ring. In this case, the suprasellar cystic tumor protruded in front of the AcoA complex to form a snowman sign (Fig. 6.17). However, this type of snowman sign can be separated easily via intracystic decompression while following the cystic wall interface. At the posterosuperior part of the tumor, the proximal PS could be exposed. The distal PS fused with the tumor capsule at the border of the diaphragmatic foramen. Here, the pituitary appeared to be inflated as an umbrella rather than displaced by compression, and thus it was difficult to preserve PS continuity. As a result, the distal segment of the PS was seceded where the stalk and tumor capsule had fused. Upon total separation of the suprasellar tumor cyst, a circular incision was made in the diaphragm at the bony opening of the pituitary fossa to locate the true subdiaphragmatic tumor capsule. Following this interface, the intrasellar part of the tumor was removed in a stepwise manner. When separating bilateral tumor walls, brisk venous bleeding is often encountered from the bilateral CS. This can be readily controlled via gentle packing with a small piece of Gelfoam (Fig. 6.19).
A typical adamantinomatous CP was identified on the pathological slides.
Postoperative course: The third VF remained intact (Fig. 6.20). Postoperatively, the patient developed mild transient DI. Hyponatremia was the major manifestation of electrolyte disturbance. The symptoms were relieved with fluid and electrolyte replacement. Endocrinological detection revealed evidence of panhypopituitarism. The patient’s visual function recovered significantly.
188.8.131.52 Case 3
This was the case of an 8-year-old female patient. She had undergone a prior craniotomy via a right pterional approach to address a significant reduction in visual acuity at a local hospital in December 2011. However, a follow-up series of MRIs indicated tumor recurrence. The patient subsequently had intermittent vomiting and constant headache.
Physical and Experimental Examination
No significant positive symptoms were observed except right eye blindness.
Radiological Images Before Surgery
The MRI scan conducted in December 2011 indicated a typical Id-CP in the intra- and suprasellar regions. This lesion was mixed cystic-solid, and the optic chiasm was displaced upward. Postsurgical MRI indicated subtotal tumor removal with residual intrasellar tumor. Follow-up MRI in April 2012 indicated intrasellar tumor recurrence. In September 2012, MRI indicated that this significant recurrent tumor remained an Id-CP with upward displacement of the optic chiasm. However, the tumor was not treated until the patient presented in our department in March 2013. CT indicated an extensive and expanding tumor in the sellar region, anterior basement of the cranial fossa, and upper clivus that also occupied the third ventricular cavity. Broad punctate calcification was observed. MRI revealed a huge mixed cystic-solid tumor in the intra- and suprasellar regions with extensive extension and external growth. The solid part of the tumor was significantly enhanced on T1-weighted enhanced MRI. The ACA and AcoA were entrapped by the cystic tumor. As a result, the tumor exhibited a lobular tumor shape (Fig. 6.21).
Analysis Before Surgery
This was a case of recurrent CP, and the notable morphological features should be emphasized. Before the primary surgery, the tumor was a typical case of Id-CP. However, the natural “protective membranous structures” such as the diaphragm and suprasellar arachnoid were destroyed by surgery so that no such interface obstructed the invagination of the recurrent tumor into the nervous tissue layer. MRI performed before the secondary surgery indicated tumor penetration through the PS and growth toward the nervous tissue layer of the infundibulum and third VF, leading to severe hypothalamic involvement.
Although the primary surgery destroyed the normal membranous structures that covered the tumor surface, the inner arachnoid layer continued to separate the tumor from the surrounding neurovascular structures. During surgery, this interface was followed to avoid injury. The most important locations were the site of origin and PS. Intrasellar recurrence is the most frequent issue, and therefore identification of the pituitary capsule was necessary to ensure total intrasellar tumor removal. After total tumor removal, the floor of the pituitary fossa was smooth and contained the neurohypophysis. The involved PS was ruptured to avoid additional recurrences (Figs. 6.22 and 6.23).
The patient developed severe water and electrolyte imbalance disorder and required fluid and sodium substitution and adjustment. Postsurgical endocrinological detection indicated panhypopituitarism. The patient’s right eye was completely blinded.
After a 1.5-year follow-up, the patient’s right eye remained blind. However, vision in the patient’s left eye was restored. She continued receiving oral prednisone, thyroxin, and desmopressin to treat panhypopituitarism and permanent DI. Her BMI increased from a presurgical value of 15.7–20.
184.108.40.206 Case 4
This was the case of a 5-year-old male patient with a 1-year history of intermittent headaches that had progressively worsened during the last 2 weeks.
Physical and Experimental Examination
The patient exhibited growth retardation and bitemporal hemianopia but no other positive physical signs. Endocrinological detection indicated hypopituitarism. Deficiencies in fT4, T3, sexual hormones, and GH were present. The PRL level was slightly increased.