Background Generally, total surgical removal of craniopharyngioma results in satisfactory outcome with a low recurrence rate, however, the location of the tumor and its adherence to the hypothalamic structures can make the operation difficult. The goal of the present study was to assess the outcome of craniopharyngiomas in 284 patients treated surgically. Methods A total of 284 patients (151 men and 133 women) with craniopharyngioma were treated surgically by our neurosurgeons from January 1996 to March 2006. Among them, 226 (79.6%) patients were adults (15 years of age or older; mean, 35.8±10.6), 58 (20.4%) were children (14 years of age or younger; mean, 9.1±3.8). The diameter of the tumors were 2.0-9.0 cm (mean, 36.54±11.4). The tumors were classified into the superior (23 patients) and inferior ventricular (261) types according to the location of the tumor relative to the third ventricular floor. For the patients with craniopharyngioma of inferior ventricular type, pterional approach was used in 191 (67.3%) patients, subfrontal approach in 17 (6.0%), and translamina terminalis through frontobasal interhemispheric approach in 53 (18.7%). For those with the tumors of superior ventricular type, transcallosal approach into the anterior third ventricle was done in 10 (3.5%) patients, and the lamina terminalis approach in 13 (4.6%). Of the 284 patients, 204 (71.8%) were followed up for 0.5 to 8 years (mean, 2.1±1.8), including 162 patients received total tumor removal, and 37 underwent subtotal or partial removal. Results Total, subtotal and partial removal of the tumors were achieved in 237 (83.5%), 34 (12.0%) and 13 (4.5%) patients, respectively. The pituitary stalk was preserved in 176 (62.0%) patients, severed in 52 (18.3%), and unidentified in 56 (19.7%). Twelve (4.2%) patients died within one month after the surgery. During the follow-up, 23 (14.1%) patients experienced tumor recurrence 1.0-3.5 years (mean, 1.8±1.6) after total tumor removal, and 24 (64.9%) had recurrent tumor 0.25-1.5 years (mean, 0.5±0.4) after subtotal or partial resection. Normal activities of daily living were regained in 63 (80%) patients, independence in 29 (14.2%), and daily life with assistance in 9 (4.4%). Four (2.0%) patients died 0.9-3 years (mean, 1.6±1.4) after discharge from hospital, 3 of them died of hypothalamic deficiency. Conclusions We can protect the hypothalamic structures and its perforating arteries by choosing surgical approaches according to the location of craniopharygioma relative to the third ventricular floor. The mortality, morbidity, and recurrence rate in patients received total resection are lower than those of patients underwent subtotal or partial resections. In addition, preservation of the pituitary stalk is critical when total tumor resection is feasible. Chin Med J 2006; 119 (19):1653-1663 Craniopharyngioma is a benign tumor that arises from remnants of the Rathke’s pouch, occurs usually around the infundibular stalk extending through the infundibulum to the anterior pituitary gland. Generally, total surgical removal of the tumor is believed to result in satisfactory outcome with a low recurrence rate. However, the location of the craniopharyngioma and its adherence to the hypothalamic structures make it difficult, if not impossible, to resect the tumor totally. When the total resection cannot be achieved, the tumor is prone to have a high recurrence rate.1-5 With the development of neuroimage and microneurosurgical technologies, the mortality rate in patients with craniopharyngioma after aggressive surgical resection has been reduced from 16.7% to about 4.0%.6-9 In the present study, we assessed the outcomes of 284 cases of craniopharyngiomas that were surgically treated by our neurosurgeons from January 1996 to March 2006.
METHODS
Patients From January 1996 to March 2006, a total of 284 patients with craniopharyngioma were treated by our neurosurgeons. Among them, 110 patients were operated at the Beijing Tiantan Hospital from January 1996 to May 2001, 69 at the Peking University People’s Hospital from June 2001 to Mach 2004, and 105 at the Capital Medical University Affiliated Fuxing Hospital from April 2004 to March 2006. The patients (151 men and 133 women) aged from 1 to 73 years, including 58 children (≤14 years; mean, 9.1±3. 8) and 226 adults (≥ 15 years; mean, 35.8±10.6). Among the patients, 97 presented moderate or severe headaches, 112 had decreased visual acuity and visual field deficits, 28 diabetes insipidus, 21 amenorrhea, 11 loss of libido, 11 growth retardation, 3 paralysis of the extremities, and 1 was asymptomatic; 67 patients experienced tumor recurrence after surgical removal, including 52 cases after primary surgical removal, 9 the second surgery, and 6 more than two surgeries. MRI showed that the tumors located at the superior sellar region in 126 patients, through the superior sella extending upwards to the third ventricular floor in 92, laterally to the parasellar region in 22, downwards to the intrasellar region in 18, at the third ventricle in 23, and purely intrasella in 3. Obstructive hydrocephalus occurred in 108 (38.0%) patients. Calcification was seen in 147 (51.8%) patients, among which 19 had calcified masses of 1.5 cm in diameter. Completely cystic mass was detected in 41 (14.4%) patients; partially cystic tumor in 154 (54.2%), and solid tumor in 89 (31.3%). The diameter of the tumors ranged from 2.0 cm to 9.0 cm (mean, 3.7±1.1).
Operations
The tumors were classified into the superior (the third intraventricular type) and inferior types according to the location of the tumor relative to the third ventricular floor.2,5,7,10 In this series, 261 patients had tumor of inferior type, and 23 superior type. In the 261 patients with tumor of inferior type, 191 (73.2%) underwent operation via pterional approach, 53 (20.3%) translamina terminalis approach through the frontobasal interhemispheric fissure, and 17 (6.5%) subfrontal approach. For pterional approach, as detailed by Yasargil,5 an incision was made at the zygomatic arch, 1 cm anterior to the tragus of the ear, and was extended up to the midsagittal plane along the hairline, 3 cm anterior to the coronal suture. Then the scalp and bone flap were elevated, the lateral aspect of the sphenoid ridge was removed with a rongeur, the dura was opened with the main flap pulled down anteroinferiorly along the region of the pterion, and the frontal and temporal lobes were retracted to expose the area along the sphenoid ridge. The bridging veins from the sylvain fissure and the tip were coagulated if necessary. The arachnoid membrane was opened to expose the carotid artery, the optic nerve, and the origin of the posterior communicating and anterior choroidal arteries. The tumor was exposed through opticocarotid, anterior chiasmal, carotico-oculomotor, oculomotor anterior, or lamina terminalis spaces, for effective resection. In our patients, most of the suprasellar craniopharyngioma involved the pituitary stalk, infundibulum, and cinereum, and extended upwards to the floor of the third ventricle resulting in obstruction of the third ventricle gradually. Some of the tumors grew downwards to the hypophyseal fossa compressing the sellar diaphragm. The tumors were isolated initially from the large displacement space of the vascular and nervous structures compressed by the tumor mass. Cystic tumors were reduced by aspirating the fluid inside, and then the capsules were resected; solid tumors were removed by piecemeal technique. After decompression, the demarcation between tumor and the cerebral structures was visible, and the tumor was separated by cutting the subarachnoid layer. Only small arterioles supplying the tumor surface were cauterized, electrocauterization of the hypothalamic structures with bipolar forceps was avoided to prevent thermal injury. Small amounts of bleeding could Fig. 1. A 47-year-old woman presented with gradual visual deterioration and amenorrhea for over 1 year. Preoperative post-contrast sagittal (A) and coronal (B) T1-weighted MRI scans showing a suprasellar craniopharyngioma with a large cystic mass extending into the third ventricle, obstructing the ventricular system partially. The tumor was resected via a pterional approach and was confirmed histologically to be an admantinomatous craniopharyngioma. Five years after the operation, sagittal (C) and coronal (D) T1-weighted MRI showing complete removal of the tumor with preservation of the pituitary stalk and the floor of the third ventricle (arrow). Fig. 2. A 47-year-old woman presented with severe headache for 2 months. Preoperative post-contrast sagittal (A) and coronal (B) T1-weighted MRIshowing a suprasellar craniopharyngioma with a large cystic component extending into the third ventricle causing hydrocephalus (arrow). The tumor was resected via a pterional craniotomy and was verified histologically to be a squamous papillary craniopharyngioma. One year after the operation, sagittal (C) and coronal (D) T1-weighted MRIshowing complete resection of the tumor with preservation of the pituitary stalk (arrow). be controlled by pressing using a cottonoid. When the tumor extended mostly into the third ventricle, the lamina terminalis was opened for resection (Figs. 1 and 2). As was often the case, the right subfrontal approach was used with initial retraction of the right frontal lobe to expose the right olfactory bulb and tract, and further deeper retraction of the right frontal lobe to expose the both optic nerves, anterior upper surface of the chiasm, right internal carotid artery, and A-1 segment of the anterior cerebral artery, and then the tumor was removed from the interoptic, carotid-optic, or carotid-tentorial spaces when the intrasellar tumors arose from the pituitary gland under the sellar diaphragm and grew into the superior sellar region with the rise of the diaphragm. The perforating arteries between the circle of Willis and the hypothalamic structures were preserved carefully during the operation. Large calcified mass was crushed into an appropriate size for remove, but if it was too large to crush and remove through the access spaces, the tuberculum could be drilled to create a large room between the optic nerves. (Fig. 3) For the 23 patients with the tumors of superior type, translamina terminalis approach through the frontobasal interhemispheric fissure was adopted in 13 (56.5%) patients, and anterior transcallosal approach into the anterior third ventricle in 10 (43.5%). For lamina terminalis approach, a bicoronal scalp flap was fashioned just behind the hairline. A right frontal osteoplastic craniotomy was made so that the medial extent of the tumor crossed the midline to expose the superior sagittal sinus and the inferior extent flush against the anterior floor of the fossa. The arachnoid cisterns were opened progressively after the right frontal lobe was retracted away from the falx. The olfactory tracts were preserved by carefully separating them from the surface of the brain, then the optic nerves and chiasm, lamina terminalis under rostrum of the corpus callosum and bilateral A2 segment of the anterior cerebral artery,
Fig. 3. A 63-year-old man presented with headache for about three years and decreased visual acuity for two months. Preoperative sagittal T1-weighted MRI (A) showing a suprasellar craniopharyngioma with a large cystic component extending into the third ventricle causing hydrocephalus (arrow). The tumor was resected via a subfrontal approach and was verified histologically to be a squamous papillary craniopharyngioma. Six months after the operation, post-contrast sagittal T1-weighted MRI (B) showing complete removal of the tumor with preservation of the pituitary stalk (arrow). and anterior communicating vessels were exposed. The tumor usually bulged forward through the lamina terminalis when it grew to push the chiasm into a prefixed position and stretch the lamina terminalis, which was frequently thinned and extended from the optic chiasm to the level of the anterior commissure. The lamina terminalis forming the majority of anterior wall of the third ventricle was incised inferior to the anterior communicating complex to isolate the tumor capsule from the optic, hypothalamic structures after the tumor was debulked. The tumor debulking was mostly achieved through the lamina terminalis if the tumor was retrochiasmatic and the optic chiasm was prefixed. The distorted pituitary stalk, which was often pushed anterior by the tumor, could be identified with its longitudinal striation and preserved by cutting the tumor off sharply. Damages to the optic chiasm, optic tracts, columns of the fornix, and hypothalamic walls were avoided carefully (Figs. 4 and 5). For anterior transcallosal approach, a right frontal horseshoe was used. The right frontal bone flap, across the sagittal sinus was centered on the coronal suture and the dura was opened. Some of the cortical bridging veins draining the superior sagittal sinus were divided to elevate the medial surface of the right frontal lobe from the falx. Then the arachnoid membrane was opened. The right and left cingulated gyri deep to the free edge of the falx, which faced and often adhered to each other, were Fig. 4. A 5-year-old boy presented with mild headache for 2 years and decreased visual acuity for 2 months. Preoperative sagittal T1-weighted MRI (A) showing a suprasellar craniopharyngioma with a predominant solid component and a cystic portion extending into the third ventricle (arrow). The tumor was resected via a translamina terminalis approach through the frontobasal interhemispheric fissure and was verified histologically to be an admantinomatous craniopharyngioma. Two week postoperatively, post-contrast sagittal T1-weighted MRI (B) showing complete removal of the tumor with preservation of the pituitary stalk (arrow). The left arrow indicating that the tuberculum sellae and the anterior wall of partial sella turcica were drilled away. It was then closed by bone wax. first separated to expose the anterior part of the corpus callosum and bilateral P2 segment of the anterior cerebral arteries. The part of the anterior corpus callosum above the foramen of Monro was incised on the anterior midline about 1 cm long, and the septum pellucidum was followed to the interforniceal fissure. The body of fornix was split longitudinally in the midline along its fibers and the septum pellucidum was opened to expose the velum interpositum. After opening the velum interpositum, the third ventricle was seen between the internal cerebral veins, and the tumor was removed piecemeally. In the end, the floor of the third ventricle was usually wide opened and the basilar bifurcation was visible (Fig. 6). The extent of removal including total, subtotal, and partial removal, depended on either the surgeon’s appreciation under a surgical microscope or postoperative contrast CT or MR image. Total resection was defined as no evidence of residual tumor while subtotal resection as a small fragments or dot of residual tumor attachment to the vascular or neural structures, and partial removal as a large portion of residual tumor, was assessed intraoperatively by a neurosurgeon. The stalks that were preserved or sectioned were confirmed by postoperative neuroimaging. A total of 129 specimens were randomly Fig. 5. An 8-year-old man presented with visual impairment for six months. Preoperative sagittal (A) and coronal (B) T1-weighted MRI showed a suprasellar craniopharyngioma with a cystic portion extending into the third ventricle. The tumor was resected via a translamina terminalis approach through the frontobasal interhemispheric fissure and was verified histologically to be an admantinomatous craniopharyngioma. Three months after the operation, post-contrast sagittal (C) and coronal (D) T1-weighed MRI showing complete resection of the tumor with preservation of the pituitary stalk (arrow). Fig. 6. A 17-year-old girl presented with regrowth of an admantinomatous craniopharyngioma 1.5 years after surgery and ventriculoperitoneal shunts twice. Preoperative sagittal (A) and coronal (B) T1-weighted MRI showing a suprasellar recurrent tumor with a large cystic component extending into the third and the lateral ventricles (arrow), causing obstructive hydrocephalus. Three weeks after the operation, sagittal (C) and coronal (D) T1-weighted MRI showing gross total removal of the tumor by a transcallosal approach to the third ventricle. from adults), and further analyzed histopathologically by neuropathologists. The histological types including squamous papillary, admantinomatous, or mixed types were compared with the morphological features on neuroimages. All the patients were followed up every 3 to 6 months in the first year after discharge from the hospital, and mail corres- pondence and/or telephone interviews were used after one year. Clinic information of presenting symptoms, neuroimages and endocrinological status of the patients were recorded.
Statistical analysis
Differences between the qualities of surgical resection and the tumor size, location, surgical approaches, and the preservation of the pituitary stalk preserved were analyzed by χ2 test. P values less than 0.05 were considered statistically significant.
RESULTS
Total, subtotal and partial removal of the tumor was achieved in 237 (83.5%), 34 (11.9%) and 13 (4.6%) patients, respectively. The relationships between the extent of resection and the size or location of the tumor are shown in Tables 1 and 2. Table 1. Relationship between extent of resection and size of tumorTumor size (cm)n (%)Extent of resection TotalSubtotalPartial < 3107 (37.7%)96 (89.7%)11 (10.3%)0 3-6146 (51.4%)130 (89.0%)14 (9.6%)2 (1.4%)> 631 (10.9%)11 (35.5%)9 (29.0%) 11 (35.5%)Total284 (100%)237 (83.5%)34 (11.9%)13 (4.6%) There was significant difference in the extent of resection among different tumor size groups (χ2=56.29，P<0.05). Table 2. Relationship between extent of resection and location of tumor Tumor locationn (%)Extent of resectionTotalSubtotalLarge partial Superior type23 (8.1%) 17 (73.9%) 5 (21.7%) 1 (4.4%)Inferior type261 (91.9%)220 (84.3%29 (11.1%)12 (4.6%)Total284 (100%)237 (83.5%)34 (11.9%)13 (4.6%)There was no significant difference in the extent of resection between the superior and inferior types (χ2 =0.98, P>0.05), indicating that classification of craniopharyngiomas relative to the third ventricular floor is equivocal in determining its resectability. The pituitary stalk was preserved in 176 (62.0%) patients, severed in 52 (18.3%), and unidentified in 56 (20.7%). The surgical approaches relative to the preservation of the pituitary stalk are described in Table 3. Table 3. Relationship between selection of surgical approach and preservation of the pituitary stalk Approachesn (%)Preservation of the PSPS preservedPS severedPS unidentifiedSuperior type23 (8.1%) Trans-LT13 (4.6%)9 (69.2%)1 (7.7%)3 (23.1%) Transcallosal10 (3.5%)5 (50.0%)3 (30.0%)2 (20.0%)Inferior type261 (91.9%) Trans-LT53 (18.6%)41 (77.6%)5 (9.4%)7 (13.2%)Pterional191 (67.3%)110 (57.6%)41 (21.5%)40 (20.9%) Subfrontal17 (6.0%)11 (64.7%)2 (11.8%)4 (23.6%) Total284 (100%)176 (62.0%)52 (18.3%)56 (19.7%)PS: pituitary stalk; LT: lamina terminalis. The PS preservation rate is significantly higher in the patients operated through the trans-LT approach (χ2 =7.47, P<0.01). The randomly selected 129 specimens was histopathologically classified into squamous papillary, admantinomatous, or mixed types. The squamous papillary was found in 103 cases, admantinomatous in 24, and mixed in 2. The relationship between the morphological and histopathological features of craniopharyngiomas is shown in Table 4.
A total of 12 patients died during the first month after the operation; the cause of death included hypothalamic dysfunction in 4 patients, diabetes insipidus or blood sodium disturbance in 3, cerebral infarction 1, operative field hematoma 1, ventricular hemorrhage 1, inhalation asphyxia 1, and deep venous thrombosis 1. One-month perioperative deaths occurred in 12 patients (4.2% of the total 284 patients, 5.1% of the 237 patients with tumors totally removed), 7 of them had undergone the second surgery because of recurrent tumors. Of the survived patients, 204 (71.8%) had follow-up for 0.5 to 8 years (mean, 2.1±1.8), 68 were lost. During the follow-up, 23 of 162 patients (14.2%), who had total resection of the tumor, suffered tumor recurrence (1.8±1.6) years after the operation (range, 1.0 to 3.5), while 24 of 37 patients (64.9%), who had subtotal or partial resection of the tumor, had tumor recurrence within (0.5±0.4) years after the surgery (range, 0.25 to 1.5). Ten of the 24 patients underwent fractionated focal irradiation therapy or γ-knife surgery. In all the patients with follow-up, 163 (80%) regained normal activities of daily living, 29 (14.2%) became independence, and 9 (4.4%) needed assistance for daily life. Four patients (2.0%) died 0.9 to 3 years (mean, 1.6±1.4) after discharge from hospital (3 died of hypothalamic deficiency, 1 died of tumor-unrelated disease). Three of the dead had total tumor resection and one had subtotal resection. Diabetes insipidus is the most common postoperative complication. Among the 284 patients, 163 (57.4%) experienced diabetes insipidus and electrolytic disorders after surgery, of which 79 (48.5%) were significantly improved to almost normal or normal without substitutive medication at early stage before discharge. Visual impairment was found in 112 patients before surgery, in 17 of them the symptom was deteriorated after the operation (15.2%). Among the 17 patients, 13 (76.5%) had partial recovery before discharge. No visual impairment was observed after surgery in the patients with normal visions at presentation. Eight patients suffered hyperpyrexia and coma because of hypothalamic damage, 3 of them died within one month after the operation, 3 was severely disabled after discharge, and 2 recovered and lived independently. Three patients had oculomotor paralysis after the operation, 2 of them recovered significantly. Postoperative hematoma occurred in 2 patients (one intraventricular and one suprasellar, respectively). There were significant differences in histopathological subtypes among different morphological features on neuroimage (χ2 = 6.85, P< 0.01).
DISCUSSION
Craniopharyngioma locating at the infundibulo-hypophyseal axis is curable and free of recurrence if the tumor is resected radically. However, the tumor usually adheres to the critical nerves and blood vessels at the hypothalamus, making complete surgical resection difficult, thus partial and subtotal resection have to be chosen, which usually leads to a higher recurrence rate than total resection.11 Recurrent craniopharyngioma usually adheres strongly to the surrounding structures of the hypothalamus, resulting in a high risk of damage to the nerves and blood vessels during the second surgery.3,6,12 Therefore, some neurosurgeons prefer aggressive surgery or complete tumor resection at the first operation to ensure a low recurrence rate and an acceptable surgical mortality.2,3,5,8 In our patients, the tumor was resected as complete as possible in the first attempt. Classification and surgical approach selection In this study, we classified craniopharyngiomas into two types, the inferior and the superior ventricular types, according to the location of the tumor relative to the floor of the third ventricle. Based on this classification we can easily choose a surgical approach to avoid damages to the hypothalamus and its perforating arteries. The tumor of inferior ventricular type of grows from the infundibulum and pituitary stalk, and extended upwards to the floor of the third ventricle. The retrochiasmatic tumor usually distorts the stalk anteriorly or laterally, pushing the optic chiasm forward, narrowing the interoptic space, and forming a pseudo-prefix. Most of the craniopharyngiomas originate from the infundibulohypophyseal axis, thus pterional approach is chosen frequently,1,3-5,7,13 by which, via anterioinferior or posteriosuperior spaces around the tumor in the suprasellar region, we can resect the tumor through several routes. The opticocarotid space is usually used to debulk the tumor initially. The spaces anterior to the optic chiasma and lateral to the internal carotid, and oculomotor space are often used to eliminate residual tumor. Some perforating arteries from the anterior cerebral and posterior communicating arteries can be retracted to further expose the floor of the third ventricle. For large calcified mass, the approach may also facilitate neurosurgeons to crush and resect the tumor by changing the microsurgical field. Through the pterional approach, lamina terminalis space can be used to excise the tumor of inferior ventricular type locating at the superior sellar region to prevent the tumor from being left behind the anterior third ventricle and supraoptic recess. When the tumor arises from the transition area of the pituitary stalk with the distalis of the adenohypophysis anterior to the subfrontal space, which is called prechiasmatic craniopharyngioma, subfrontal approach should be adopted. For most of the retrochiasmatic craniopharyngiomas, translamina terminalis approach via either frontobasal interhemispheric fissure or pterional approach are suitable, through which the floor of the third ventricular is stretched very thin and may actually be coapted with the lamina terminalis forming a “coapted membrane”. The membrane behind the chiasm is wide, and the yellowish tumor can be easily observed between the optic tracts through it. Since both the infundibular and supraoptic recesses are obliterated, the membrane can be excised instantly to access to the tumor below the hypothalamus without entering the third ventricle. Because of the chronic compression by large tumor, hypothalamic nucleus displaced laterally, thus the excision of the coapted membrane through translamina terminalis approach will not damage the hypothalamus. Via the opened coapted membrane, the tumor dome can be removed directly from the third ventricular floor, then the tumor behind or in front of the chiasm and that invading the stalk can be resected subsequently.
Recently, Fahlbusch and colleagues1 pointed out that the pterional approach is relatively narrow for large retrochiasmatic or retrosellar tumor, when the optic chiasm is pushed anteriorly and the lateral view through the opticocarotid space is obstructed by the perforating arteries. Several authors advocate that frontobasal interhemispheric approach via the translamina terminalis space, which offers a good surgical field, is feasible to assess craniopharyngiomas extending into the third ventricle and the suprasellar cistern. In other reports, frontobasal interhemispheric approach is useful for all craniopharyngiomas.13-15 In our series, opening the translamina terminalis via the pterional approach is available for large retrochiasmatic craniopharyngiomas. In recent 3 years, we seldom use the transcallosal approach to resect intraventricular tumors because of the long distance to the anterior third ventricle and to the suprasellar region. Furthermore, the operative field of the transcallosal approach is narrower than that of the translamina terminalis through the frontobasal interhemispheric approach. Purely intraventricular tumor, which is rare, can be excised by transcallosal approach. It is hypothesized that most of the intraventricular tumors arise from the pars tuberalis containing remnants squamous epithelium or Rathke’s pouch, grow along the pituitary stalk, and extend to the infundibulum or tuber cinerum in the floor of the third ventricle. When the floor of the third ventricle is pushed by the tumor, it becomes so paper thin that the tumor can protrudes into it directly. Craniopharyngiomas possessing only a large intrasellar part are infrequent on preoperative images.2,8,10 Most of the inferior type tumors grow inferiorly, protrude into the sella turcica via the thinned diaphragm. In our series, 9.5% of the inferior type tumors were intrasellar or infradiaphragmatic tumors, for which the subfrontal approach is suitable. The tumor may expand widely into the sella and invade the sphenoid sinus; the inferior capsule of the tumor often adheres tightly to the dura of the dorsum sellae and the sphenoid mucosa, as well as the medial and superior walls of the cavernous sinus if the sella floor is eroded. In order to access the inferior portion of the tumor at the sellar floor, we prefer to drill away the tuberculum sellae and the anterior wall of the sella turcica to create a large opening between both the optic nerves, which allows us to remove the inferior pole of the tumor tightly adherent to the dura of the dorsum sellae and the sphenoid mucosa.
Preservation of pituitary stalk and perforating arteries
Preservation of the stalk is the key point to prevent diabetes insipidus and electrolyte disturbance after aggressive resection of craniopharyngioma, and to gain recovery of normal endocrine function quickly and completely. The pituitary resected is closely associated with hormonal deficiencies that result in permanent panhypopituitarism.8,16,17 Normally, the stalk is recognizable by its location and striate appearance which run vertically along its surface. However, a large tumor may significantly change the appearance of the stalk and displace its course. Large calcium mass confluent from small foci of calcium always deposits and invades the stalk, and distorts its structure. Retrochiasmatic cranio- pharyngioma, which grows posteriorly to the chiasm, usually push the pituitary stalk forward and the chiasm forward and upward, prefixing the optic nerve falsely. The tumor can be removed safely and easily away from its retrochiasmatic location at the level of the third ventricular floor by opening the lamina terminalis. In our cases, we simply pushed the tumor downward and anteriorly to prevent the stalk from obstructing the anterior view of the chiasm when applying the subchiasmatic route initially. Prechiasmatic and subchiasmatic tumors often push the stalk backward and the chiasm upward, postfixing the prechiasm. When cutting the tumor between both the optic nerves, we widened the distance between both the nerves and expand the prechiasmatic space to ensure tumor resection and stalk preservation In our series, the stalks were preserved in 64.9% of the 284 patients. The rate of stalk preservation was in an order from high to low in translamina terminalis, subfrontal, pterional, and transcallosal approaches. Preservation of the perforating arteries in the hypothalamic structures is critical to prevent fatal postoperative complications in addition to protection of large arterial segments constituting the circle of Willis during surgery.18 The feeding arteries to the tumor usually arise from the perforating arteries originating from the arterial segment of the circle of Willis, which commonly distributes blood flow to the hypothalamus around the tumor. Blood flow to the floor of the third ventricle is supplied by three perforating arterial groups: 1) The perforators from the anterior cerebral and anterior communicating arteries, which supply the superior part of the hypothalamus, including the anterior superior chiasm and the lamina terminalis. Particularly, Heubner’s artery from A1 segment of the anterior cerebral artery is subject to injury during opening the lamina terminalis space. This perforating artery terminates in the anterior part of the caudate nucleus, the anterior third of the putamen, the tip of the out segment of the globus pallidus, the limb of the internal capsule, and the anterior perforated substance.3 2) The superior hypophyseal arteries from the internal carotid artery supplies the optic nerve, chiasm, optic tract, stalk, infundibulum, median eminence, tuber cinereum, and mamillary bodies, which is vulnerable to damage when dissecting the tumor through the anterior chiasm and lateral optic nerve spaces.19 3) The premamillary arteries arising from the posterior communicating artery, and terminating mostly at the stalk, infundibulum, median eminence, tuber cinereum, mamillary bodies, and anterior perforated substance. These arteries are vulnerable to injury when dissecting the tumor through the lateral optic nerve and the lateral internal carotid artery spaces.9,20,21 Usually, the tumor is not supplied by the perforating arteries from the basilar posterior circulation.2,3,4 However, recurrent tumors or the tumors extending to the interpeduncular fossa appear to cause adherence between the perforating arteries from the posterior circulation complex. When dissecting the superior and posterior parts of the tumor, care should be taken to the posterior thalamoperforating arteries supplying the interpeduncular fossa, posterior perforated substance, and mamillary bodies. These arteries are critical for the function of the spinothalamic and pyramid tracts and reticular formation in the midbrain.9,22,23
Based on our experience, the perforating arteries from various arterial segments of the Willis’ circle include non-branching perforator and perforating complex. The stem of perforating complex is thicker and larger in diameter than that of the non-branching perforators. Thus, when the stem of the perforating complex is damaged, the hypothalamus will be ischemic in a large extent. Therefore, elec- trocauterization of these small arterial feeders should be avoided on the surface of the tumor. In addition, attention should be paid to the perforators to the anterior perforated substance, which are fine twigs originating from the bifurcation of the internal carotid artery and the initial segment of the anterior and middle cerebral arteries. The spasm of these perforators, which results in ischemia of the internal capsule, putamen nucleus, and hypothalamus, can be caused by excessive stretches and long exposure of the sylvian fissure vessels when pterional approaches is employed.
In our series, two patients suffered contralateral hemiparalysis due to ischemia of the basilar
ganglia from infarction of the anterior perforated substance perforators. Excision extent and clinical/pathological featuresEvaluation of the extent of tumor resection depends on early postoperative CT scan and MR images. Histologically, there is no cleavage plane between the dome of the tumor and the infundibular stalk and the floor of the third ventricle because of an intensive glial reaction in this region of the brain, where most of the craniopharyngiomas grow finger-like projections into the floor of the third ventricle. The island of the tumor surrounded by neural tissue are demonstrated on histological sections but can not be revealed on the early postoperative neuroimages. van Effenterre4 suggested that postopera, tive MRI was reliable only for macroscopic fragments of residual tumor but not for microscopic infiltration of the nerve parenchyma. .We suggest combination of intraoperative observation and postoperative MRI for early postoperative judgment of the quantity of tumor removal. Further prediction of tumor recurrence depends mainly on 3-month postoperative MRI, when false image following surgery may disappear and the disturbed anatomical structures returns to the normal. The patients with total resection in this study did not receive postoperative radiotherapy and were followed up by neuroimaging. In the 23 patients suffered tumor recurrence after total resection, 14 (61%) had recurrent tumor in the infundibular stalk and the third ventricular floor, 8 (35%) the infradiaphragmatic region. and 1 the interpeduncular cistern. In this series, surgical removal remained the first choice for patients with recurrent tumor, because radiotherapy carries high risk of radiation-induced adverse effects in a long term. Microsurgical intervention is recommended for large tumors and ones without clear boundary between tumors and surrounding critical structures. Radiotherapy was an alternative to treat recurrent tumor after more than three surgeries or for patients who can not tolerate surgery.
The characteristics and quality of resection of craniopharyngiomas are different in children and adults because of the different pathological features.10 Admantinomatous tumor, which is more common in children than in adults, adheres to nerves and blood vessels often and therefore may be less feasible for gross total resection. Adult patients are more likely to harbor squamous papillary tumor and benefit more frequently from gross total resection.6,27 The cystic formations of the tumors facilitates total removal of the wall because the cystic wall collapses after being tapped, providing larger space for manipulation. Adamson et al11 reported that most of the squamous papillary tumor is solid and uncalcified. Usually, the tumor had good outcomes and few recurrences. It can be found in one-third of adult patients, but, rare in children. The admantinomatous tumors with calcification and cystic changes always adhere to the infundibular stalk and infiltrate into the floor of the third ventricle, resulting injury during surgery frequently. On the other hand, the solid squamous papillary tumors, which are always uncalcified, can be resected completely without serious damage to the hypothalamus. Weiner et al27 stated that the most significant factor associated with the recurrence of craniopharyngioma is the extent of resection rather than the histopathological subtype of the tumor. In another report of 48 squamous papillary tumors, there were no significant difference between the squamous papillary and admantinomatous tumors in resectability, efficacy of therapy, and overall survival.28 In this study, we did not observe a significant difference in tumor recurrence between the two subtypes of the tumor after total resection. In our experience, complete resection is influenced by the calcification adhering to the major arteries and the thin cyst wall to the hypothalamus. The huge calcified mass and thick rigid cyst wall that adhere to or invade the stalk often injure the stalk, especially in
cystic tumor of the squamous papillary type in adults. Moreover, proliferative activity of the tumors and its penetration into the hypothalamic structures often make radical resection difficult.
Conclusion
Although no consensus exists regarding the optimal management of craniopharygioma, we propose to simply classify the tumor into two types, the superior and inferior ventricular types according
to its origin relative to the floor of the third ventricle. Based on our experience of 284 patients with cranio- pharyngioma, this classification provides a good mean to choose surgical approach, allowing protection of the hypothalamus and its perforating arteries with lower mortality, morbidity, and recurrence rate in the patients with total tumor resection than in those with subtotal or partial tumor resection. In addition, the pituitary stalk should be preserved carefully when complete resection of the tumor is tentative, because it is a critical role for recovery of the hypothalamus and pituitary gland functions.
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(Received March 29, 2006)
Edited by LUO Dan
