Surgery for Craniopharyngiomas Treatment & Management

No primary medical therapy exists for this tumor. Hormonal replacements are administered as needed if endocrine abnormalities exist.

The initial surgical decision concerns the approach. If the predominant portion of the tumor is intrasellar, the approach is usually transsphenoidal. Often, the suprasellar component can be delivered into the sella and evacuated. Further, the transsphenoidal approach is well tolerated by patients and is preferable to a craniotomy, when feasible.^{[11, 12, 13, 14, 15, 16, 17, 18]}

If the pituitary sella is not enlarged, the transsphenoidal approach is generally not preferred. A craniotomy is usually necessary when the predominant component is suprasellar, although certain suprasellar masses may be located through an extended transsphenoidal approach. This approach is also useful for lesions that have a relatively small suprasellar extension.

The pterional craniotomy is the standard craniotomy approach to suprasellar lesions because it allows good visualization of the optic nerves, chiasm, and surrounding structures. Variations of the pterional craniotomy have been proposed to include resection of the orbital rim and zygoma so as to provide a more defined view of the skull base and thereby allow better access to the superior aspects of this tumor. These approaches lend themselves to less frontal lobe retraction in order to visualize the operative site.

A subfrontal approach is appropriate for lesions that lie anterior to the optic chiasm, but this may be difficult to determine preoperatively. Under rare circumstances, a transcallosal approach is necessary when the tumor is entirely within the third ventricle. The drawback to this approach is the inability to identify the optic chiasm and pituitary stalk early in the dissection.

Cystic tumors are amenable to either a transsphenoidal approach or a pterional craniotomy. The solid components often adhere to the optic chiasm or hypothalamus and, therefore, may be difficult to remove in their entirety.

Cyst aspiration combined with intracavitary phosphorus-32 (³² P) instillation is an alternative to traditional surgical resection (see video below). Good long-term control of tumor growth has been demonstrated; however, a tumor with significant solid components is not likely to respond to³² P.^[19]

Grading

In an attempt to balance the advantages of an aggressive surgical resection against the risk of significant morbidity, a preoperative grading system (for children) has been proposed. This system considers the extent of invasion of the hypothalamus by the tumor and is as follows:^[20]

• Type 0: The tumor represents no hypothalamic involvement.
• Type 1: The tumor distorts or elevates the hypothalamus, but the latter is still visible.
• Type 2: The hypothalamus is no longer visible.

Consequently, some proposed that a gross total resection be attempted in type 0 and type 1 tumors and that a subtotal resection be attempted in a type 2 tumor, leaving only the hypothalamic component. Although this grading system was developed in a pediatric population, applying it to an adult population is certainly feasible. Some evidence exists, however, that the craniopharyngiomas that arise in adults are less likely to invade the hypothalamus.

A newer classification system proposed by Kassam et al uses a scheme that divides tumors according to their suprasellar extension, based upon the endoscopic expanded endonasal approach (EEA), and is as follows:^[21]

• Type I - Preinfundibular
• Type II - Transinfundibular (extending into the stalk)
• Type III - Retroinfundibular, extending behind the gland and stalk, and has 2 subdivisions (IIIa, extending into the third ventricle; and IIIb, extending into the interpeduncular cistern)
• Type IV - Isolated to the third ventricle and/or optic recess and is not accessible via an endonasal approach

Preoperative workup includes an endocrinologic evaluation, particularly to exclude hypoadrenalism and hypothyroidism, both of which increase surgical mortality rates. Dexamethasone may be started prior to surgery to decrease edema.^[22]

Successful transsphenoidal resection of a craniopharyngioma requires a generous removal of the contents of the sella turcica. Adequate suprasellar decompression occurs when the arachnoid membrane that surrounds the tumor descends into the operative field. Cerebrospinal fluid (CSF) leakage occurs if the arachnoid is disrupted.

The goal of a craniotomy is gross total removal of the tumor with preservation of the optic apparatus and pituitary stalk. Understanding the anatomy in this region is key to accomplishing this goal. The optic chiasm is nearly always elevated, and the pituitary stalk is usually displaced posteriorly. The stalk may be identified by the striate pattern of portal vessels along its surface. The lamina terminalis may need to be opened for access into the third ventricle. The goal of tumor removal must not outweigh the need for preservation of neural structures; therefore, leaving undisturbed a tumor that is densely adherent to the optic apparatus, anterior cerebral artery, or hypothalamus is advisable.

In general, because long-term tumor control is excellent with radiation therapy following subtotal tumor removal, a conservative approach to tumor resection is usually advised.^[23] In some patients, however, a good cleavage plane exists between tumor and brain, and a true complete resection can be accomplished. Surgical judgment is crucial in the assessment of this possibility.

Performing a full postoperative endocrine evaluation as well as repeated imaging studies is advisable. MRI scans are typically obtained immediately postoperatively (within 48 h) and then at periodic intervals.

The most common complications are related to injury of the adjacent neural structures. Vision may worsen because of unavoidable optic apparatus manipulation.^[24]

Postoperatively, many patients demonstrate hypopituitarism. In order to offset this, they are usually given physiologic doses of hydrocortisone as well as a dexamethasone taper to decrease the edema associated with the surgical approach.

Diabetes insipidus may develop and may require treatment with fluid replacement and, occasionally, vasopressin or its synthetic analogue, desmopressin. Some patients have diabetes insipidus as well as disruption of their thirst sensation. These patients pose a difficult management problem and are at high risk for developing hypernatremia. Injuries to the hypothalamus can cause other behavioral changes, including caloric balance disturbance, memory disturbance, and changes in affective behavior.

In rare cases, development of radiation-induced gliomas may occur. This long-term complication has a latency period of greater than 10 years, frequently involves the temporal lobe, and has been predominantly reported in patients who underwent conventional fractionated radiotherapy in their childhood.^[25]

Total resection is the best chance for cure, although some series have reported good results with subtotal resection and fractionated radiation therapy. Small residual tumor, confirmed on postoperative MRI, is generally treated with external beam radiotherapy; however, stereotactic radiosurgery has been used. The use of proton beam radiotherapy for residual disease is currently being investigated. Although the amount of radiation is limited by the proximity to the optic chiasm, good long-term results are now being reported after radiosurgery.^{[26, 27, 28, 29, 30]}

Adverse effects of radiation therapy include endocrine dysfunction, optic neuritis, dementia, and radiation necrosis. In addition, radiation can induce tumors such as meningiomas, sarcomas, and gliomas. In pediatric cases, radiation is postponed to minimize its effects on intelligence quotient and growth. Survival rates for patients with surgery and radiation are better than with surgery alone because radiation helps deter regrowth when residual tumor is present.^[31]

Brachytherapy has also been used to treat cystic craniopharyngiomas. Radioisotopes are placed into the cystic portions of the craniopharyngioma. Phosphorus-32 (³² P), colloidal gold-198, colloidal yttrium-91, and bleomycin have all been used. Bleomycin causes shrinkage of the cyst but is highly toxic to neural structures.

In a 1992 review of brachytherapy for craniopharyngiomas, Van den Berge followed 31 patients for an average of 41 months.^[32] Twenty-nine percent showed improvement of visual acuity, while 13% had stable visual acuity, and 58% deteriorated. Similarly, 28% showed improvement of their visual fields, with 20% showing no change, and 52% deteriorating.

Mortality and morbidity

Overall, the surgical mortality rate is less than 5%, mostly from hypothalamic injury. Bilateral hypothalamic injuries lead to hyperthermia and somnolence. The 5-year survival rate for tumor treatment is 55-85%.

Recurrence most commonly occurs within the first year, with a few reports of recurrences after 3 years. Morbidity and mortality rates are higher with recurrences. Hoffman followed 50 children with craniopharyngiomas.^[15] In his 1992 report, 90% had total excision, and tumor recurred in 34%. Of all 50 children, 56% were leading normal or nearly normal lives, often requiring endocrine replacement. Twenty-four percent were able to function reasonably well and to attend school despite intellectual, visual, or weight problems; 8% were significantly handicapped; and 6% died.

The largest divide in the treatment of craniopharyngiomas regards whether to perform a gross total excision or perform a subtotal resection followed by radiation therapy. Retrospective series support both philosophies. Surgical judgment must temper the enthusiasm for gross total removal at all costs. The use of 3-dimensional conformal radiation treatment (3D CRT), stereotactic radiosurgery (SRS), stereotactic radiotherapy (SRT), and intensity-modulated radiation therapy (IMRT) will further allow treatment of small tumor residua with little risk of neurologic deficit.^[33]