Diagnosis Pathology Surgical Treatment Radiation Shunting Results

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Operative Procedure

The best route of approach will depend on the shape, size, and direction of growth of the individual craniopharyngioma. The location of cysts, which often create a path to the solid portion of the tumor, may also affect the choice of approach. Certain general principles can be defined. The approach chosen should offer the greatest exposure of tumor to subarachnoid pathways at the cranial base. Approaches that do not sacrifice or divide neural structures are generally preferred to those that do. Unilateral approaches are to be preferred over those that mobilize both sides of the brain.

The two approaches most commonly used are the subfrontal and pterional approaches. Both of these routes allow the surgeon to approach the tumor below the circle of Willis, with excellent visualization of the nerves and chiasm. The pterional route is the shorter approach, and allows good visualization of the retrochiasmatic area. The subfrontal approach allows excellent visualization of the anterior portion of the optic pathways, as well as a direct approach through the lamina terminalis if required. Both approaches can be subdivided into a number of different pathways, as follows.

1. Subchiasmatic pathway. This is the traditional approach between the optic nerves.

2. Opticocarotid pathway. This route, between the internal carotid artery and the optic nerve and tract, is useful when the chiasm has been pushed forward by tumor and appears to be prefixed, with shortened optic nerves.

3. Lamina terminalis pathway. The lamina terminalis may be exposed above the chiasm and divided between the optic tracts. Opening the lamina terminalis often does not expose the tumor, because it is covered by the thinned floor of the third ventricle. The floor may be opened, or it may be possible to displace the mass downward ad remove it subchiasmatically or laterally.

4. Pathway lateral to the carotid artery. Opening the arachnoid at the rostral end of the sylvian fissure and retracting the temporal pole may give access to the lateral tumor surface.

5. Transfrontal-trans-sphenoidal pathway. It requires drilling away the tuberculum sellae, opening the sphenoid sinus, and removing the anterior sellar wall. This approach is useful when the chiasm is prefixed and the tumor fills the sella. It may be employed with opening of the lamina terminalis. I find a more restricted drilling of the tuberculum to be adequate, and I try not to enter the sphenoid sinus, instead leaving its mucosa intact.

6. In case of giant craniopharyngioma with massive intraventricular extension with the superior cystic part pushing up the foramen Monro , it is wise to attack the tumor through interhemispheric transcallosal or transcortical transfrontal approach directly to the lesion, taking into consideration the geometry of the tumor and the best visual access to the most parts of the tumor as in this case.

As the tumor is approached, each of the possible routes is evaluated, and the greatest possible exposure of the tumor surface is sought. When the tumor is retrochiasmatic. the chiasm will appear to be prefixed because of displacement from behind. Much has been written of "short" optic nerves, but some of the "prefixity" is lost during the course of operation. Lateral displacement of the optic tract is due to a similar mechanism, distorting the tract and decreasing the space between its lateral surface and the carotid artery.

When a portion of the tumor is exposed, the arachnoid covering the tumor is carefully opened. Care is taken not to coalesce the arachnoid with the tumor capsule by using the cautery, as preser­vation of the subarachnoid CSF plane is necessary for safe and total tumor removal. A needle is inserted into the tumor and the cyst is aspirated. All tumors should be aspirated, even ones that appear solid on MRI or CT, since the latter may be partially cystic, and removal of only I or 2 ml may provide room for dissection. Entering the tumor with a small microsuction tip will further de­compress the tumor. As the tumor mass decreases, more of the capsule can be exposed by dissecting in the subarachnoid CSF plane around the tumor. Small arterial feeders from the anterior circulation to the tumor may be coagulated and divided, remembering that the plexus of small arterial feeders to the undersurface of the chiasm and optic tracts must be spared. Fortunately, little blood supply is derived from the posterior portion of the circle of Willis, and the caudal surface of these tumors is usually, but not always, less adherent. The interior of the tumor is entered, and the solid portion removed piecemeal. As these fragments are removed, care must be taken to protect the optic nerve and tract, especially from the calcified fragments. Larger calcifications should be crushed to an appropriate size for removal. The internal carotid artery must be protected as well, and fusiform dilations of the carotid on the operative side have been reported. As the tumor is progressively gutted, portions of the capsule can be resected. It is important not to "lose the handle," however, as the capsule would then retract upward out of sight and might prove impossible to retrieve. After the attachments of the tumor to the optic apparatus, hypothalamus, and basal arterial vessels have been dissected with higher microscopic magnification, the tumor remnant is usually easily delivered. Small angled dental mirrors are then used to inspect the undersurface of the chiasm and the median eminence region for tumor remnants.

Alternative Approaches

The trans-sphenoidal route has been widely employed for removal of tumors that are largely intrasellar or have only small suprasellar components. Larger tumors, with greater suprasellar extension, may be removed by those skillful in this approach. A suprasellar extension with a smooth contour may indicate an intact diaphragma sellae that is stretched upward by the tumor mass. The trans-sphenoidal route is often best in such a case, as it allows direct access to the tumor while the intact diaphragma helps protect the undersurface of the brain.

In one series of trans-sphenoidal operations, many of the tumors involved had little in the way of sellar enlargement. An anteriorly displaced pituitary gland was a frequent finding, necessitating division of the pituitary gland to achieve tumor removal with preservation of endocrine function.

This approach is not applicable when the sella is normal in size, when pituitary function is totally intact, or if the suprasellar portion of the tumor extends laterally or anteriorly away from a direct line of approach through the sella. Long-term follow-up studies after trans-sphenoidal removal have shown both good control of tumor recurrence and surprisingly good endocrine function. Laws has described a case in which the removal of a densely calcified tumor trans-sphenoidally resulted in damage to both carotid arteries and death.

The transcallosal approach may be chosen for tumors that lie largely in the third ventricle. It is most useful when the intraventricular portion is solid or calcified or when no portion of the tumor can be visualized in the basal subarachnoid pathways. A number of cases in which the craniopharyngioma was totally within the third ventricle have been described. The transcallosal approach for craniopharyngioma was first reported in 1973. Since then this operative approach has become increasingly familiar to neurosurgeons, and its technique has been well described.

This approach is most useful when the foramen of Monroe is widely dilated, either by the tumor or by hydrocephalus. When the transforaminal route is not available, it may be necessary to use either the interforniceal approach described by Apuzzo or the subchoroidal approach. It is better to avoid enlargement of the foramen of Monroe by dividing the fornix, because of concern about memory problems. Two vascular problems have arisen in the use of this approach. The first is vasospasm of the anterior cerebral arteries as they are dissected and retracted; the second is damage to or obstruction of the deep venous system as the third ventricle is entered.

Preserving the Pituitary Stalk

The pituitary stalk is necessary for the resumption of normal pituitary responses, and its preservation is now possible with microscopic visualization. Even if the stalk is damaged, a remnant that reaches from the median eminence to the pituitary will serve as a matrix on which the important portal system may reform. Recognizing the stalk is basic to preserving it. Under higher magnification, the stalk has a striate pattern that is distinctive among neural structures. This striation is caused by the parallel arrangement of the long portal veins and is maintained despite severe distortion of the stalk. Once the stalk is visualized, it is often possible to dissect the tumor away without sacrificing the stalk. While the stalk has been described as lying on the posterior surface of the tumor, it may be found displaced laterally or anterolaterally as well. Patients with an intact stalk appear to regain endocrine function more quickly and complete than other patients, and a case has been described of total removal without postoperative diabetes insipidus.

Staged Procedures

Occasionally it is desirable or necessary to perform a two-stage procedure to achieve total tumor removal. Koos and Miller have described a procedure in which intracranial removal of the supra­sellar portion of the tumor was followed by trans-sphenoidal removal of intrasellar tumor at a later operation.

Some tumors have extensions that make removal by any single route hazardous or unfeasible. When the tumor has large suprasellar, retrosellar, and third-ventricle components. A portion of the tumor has pushed laterally through the choroid fissure, and a large component is located in the temporal horn. Midline portions of the tumor are removed via a subfrontal approach at first operation, and the temporal cyst was aspirated through its medial surface. The calcified portion in the temporal horn and a large calcified interpeduncular fragment are excised in a subsequent transtemporal procedure.

False Cure

Virtually every large series of craniopharyngiomas has reported recurrences of tumor after "total" removal. Amacher has reviewed several series and has documented 17 recurrences after 92 total removals. Other reports show that even use of the operating microscope and careful examination with micromirrors may not prevent the operator from thinking that total removal has been achieved when it has not. Routine use of MRI postoperatively will reveal many, if not all, of these residual tumor fragments. When postoperative MRI is required as a criterion of total removal, the false-cure rate can be expected to fall.

Postoperative Management

Most patients who undergo total or radical subtotal tumor removal will have either temporary or permanent disruption of neurohypophyseal axis function. Damage to the stalk or pituitary may result in various endocrine deficiencies, of which loss of adrenocorticotropic hormone (ACTH) and antidiuretic hormone (ADH) will be notable in the immediate postoperative period. Loss of other endocrine functions is important in the long-term management of these patients.

Lack of corticosteroid production secondary to loss of ACTH production is rarely a problem in patients who are receiving large doses of high-potency synthetic corticosteroids, which are used in most centers to control cerebral swelling. Because these synthetic steroids have little mineralocorticoid effect, some workers have advocated using cortisone acetate in physiological doses in addition to the high-potency agents. As the risk of edema lessens, the synthetic steroids are tapered off, and cortisone replacement at a physiological dosage is given. These patients must be regarded as being hypoadrenal at all times, and death of a patient during a metyrapone test has been reported.

Diabetes insipidus is noted shortly after the operation but may begin during the surgical procedure; it is best managed initially by fluid replacement. If excessive thirst or fluid replacement problems become difficult for the patient, vasopressin may be given, preferably in a short-acting form. Patients who have diabetes insipidus due to stalk sectioning may have subsequent involution of neurohypophyseal axons or infarction of a portion of the pituitary, caused by interruption of the blood supply from the portal vessels. ADH may then be released from the degenerating axon terminals in superphysiologic amounts. When these events occur, they usually take place from 48 to 96 h after stalk damage. Patients who have been given long-acting vasopressin may be at risk for renal shutdown under these circumstances. Experience at many centers, including mine, with synthetic DDAVP (desmopressin acetate) spray has been satisfactory. Determinations of fluid intake and output, urine specific gravity, and rate of urinary excretion at 2-h or 3-h intervals are helpful in the immediate postoperative period. Daily or twice-daily blood counts, serum electrolyte determinations, and accurate patient weight measurements are also needed. Operative deaths are usually attributed to hypothalamic injury, which causes a clinical syndrome characterized by hyperpyrexia and somnolence. Damage to osmoreceptors in the anterior hypothalamus may lead to loss of the sensation of thirst. Patients are then difficult to manage, as thirst is a major factor in the treatment of the concomitant diabetes insipidus. Other postsurgical hypothalamic deficits may include disturbance of caloric balance, changes in wakefulness, changes in affective behavior, and disturbances of memory.

Author's approach:
The author prefer using combined bifrontal subfrontal approach with pterional modification according to the location of the tumor. Mobilization and preservation of the olfactory tracts is performed routinely. Inspection of 220 degrees around the chiasmal region is possible, giving the surgeon all the abilities to perform all needed maneuvers. For demonstration click here!

Photo showing the cavity medial to the left olfactory trigon and the empty space after removal of the solid mass between the ICA and the left oculomotor nerve. It was possible to see the basilar artery inside the cavity. 

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