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Bifrontal basal interhemispheric approach for midline suprasellar tumors: Our experience with forty-eight patients
Correspondence Address: Source of Support: None, Conflict of Interest: None DOI: 10.4103/0028-3886.125247
Introduction: Suprasellar lesions present a surgical challenge due to their complex relationship with surrounding neurovascular structures. Of the approaches for these lesions, bifrontal basal interhemispheric approach (BBIA) gives a midline perspective of suprasellar anatomy and has certain advantages over lateral approaches. Materials and Methods: We retrospectively reviewed 48 patients with suprasellar lesions operated over 7 years via BBIA. Patient records, operation notes, radiology, and outpatient files were scrutinized to collect data. Results: During the study period 48 patients (mean age 33 years, M:F 1.5:1) were operated by this approach. The clinical features included: Visual field deficits in 33 (69%) patients, with 6 of them being blind, diabetes insipidus in 7, growth retardation in 5, and subarachnoid hemorrhage in three patients. Cranopharyngiomas (52%) and meningiomas (16.7%) were the most common pathologies. Dyselectrolytemia (18, 40%) and diabetes insipidus (15, 33%) were the most common complications. Postoperative seizures, meningitis, subdural effusion, and retraction site contusion were seen in 12 (27%), 5 (11%), 4 (9%), and 1 (2.2%) patient, respectively. Three patients died postoperatively and 19 (40%) patients required hormone replacement therapy. Amongst the patients with preoperative visual deficits, 23 (70%) had improvement in visual functions, in six (20%), there was no change and four (8.3%) patients had visual deterioration. Conclusion: BBIA provides a true midline perspective and orientation, and permits complete and safe removal of midline suprasellar lesions in majority of cases. This approach is especially useful in retrochiasmatic tumors and in residual/recurrent tumors providing virgin plane of dissection. Keywords: Bifrontal, basal interhemispheric approach, outcome, suprasellar tumors
Suprasellar lesions present a significant surgical challenge. Different surgical approaches used for these lesions include: Pterional, subfrontal, subtemporal, transcortical, transcallosal and interhemispheric. [1],[2] Due to its complexity and associated morbidity, the interhemispheric approach was previously avoided. However, with the advances in microneurosurgical techniques and with improvization in neurosurgical instruments, the interhemispheric approach can be safely used for managing lesions in the suprasellar region. [1],[2],[3],[4],[5],[6] The traditional interhemispheric approach is a complex approach with an associated risk of damage to olfactory tracts and disturbances of psychological functions postoperatively. [7] In order to reduce the risk of olfactory dysfunction and psychological disturbances as well as to better visualize the infundibulohypophyseal axis, Shibuya et al. [6] and Shirane et al. [8] modified traditional interhemispheric approach, the fronto-basal interhemispheric approach which combines the basal interhemispheric approach and the translamina terminalis approach. In this study, the authors present the technical aspects of the bifrontal basal interhemispheric approach (BBIA) and share their experience of 48 patients with suprasellar intradural lesions treated with this approach.
This is a retrospective study conducted at a tertiary care neurosurgical centre. Patient records, operation notes, radiology, and outpatient files were scrutinized to collect the data. Between January 2006 and December 2012, we have operated 48 patients (mean age 33 years, range 3-60 years, M:F 1.5:1) with suprasellar lesions via BBIA [Table 1].
Clinical manifestations The mean duration of symptoms was 6.6 months (range: 3-72 months). The most common presenting complaint was headache present in 36 (85%) patients. Thirty-three (69%) patients had visual field defects, six of them had blindness, seven patients had diabetes insipidus, five patients had growth retardation, three patients presented with subarachnoid hemorrhage, and two patients had diencephalic syndrome [Table 2].
Complete hormonal profile was done in all the patients and nine patients were found to have anterior pituitary hormonal imbalance. Operative technique All the patients underwent primary surgery and in all gross total excision of tumor was attempted. After induction and intubation, patient was positioned supine with head fixed in mild extension (5-10°) with a three pin fixation system. A bicoronal scalp incision [Figure 1]a was given behind the hairline and a subgaleal flap was raised followed by elevation of pericranium upto bilateral orbital rims. The pericranium was reflected anteriorly for future use to exteriorize frontal sinus.
A low bifrontal craniotomy was made including the nasal part of frontal bone after making a single midline burrhole. The frontal air sinus was opened invariably and sinus mucosa was excised to prevent mucocele formation. The sinus was then packed with betadine-soaked gelfoam and sealed with bonewax. This step was done painstakingly with great efforts, in order to prevent cerebrospinal fluid (CSF) rhinorrhea in the postoperative period. A pedicled pericranium was then used to exteriorize the sinus by suturing pericranium to dura caudal to dural suture line. The dura was opened in a transverse fashion on either side of midline [Figure 1]b, as far forward as possible. The superior sagittal sinus was then ligated with a figure of eight silk suture and divided as far forward as possible and falx was divided down till the crista galli. Both the frontal lobes were retracted and olfactory tracts dissected from the frontal lobes bilaterally, till olfactory trigone [Figure 2]a and b. The inclusion of nasal part of frontal bone in craniotomy allows dissection of basal interhemispheric fissure, thereby avoiding damage to draining veins over convexity. Further gentle retraction of frontal lobe would expose chiasmatic and lamina terminalis cisterns which are opened to let CSF out, thereby making brain lax and minimizing the need of frontal lobe retraction.
The tumor was then removed in a sequential manner depending upon pathology and directions of tumor extension. In case of craniopharyngiomas, tumor removal was started from carotico-optic space, interoptic space, and the corridor lateral to carotid artery. Thereafter, lamina terminalis was opened [Figure 2]c-e and tumor taken out piecemeal from within third ventricle. Extreme caution was taken to avoid spillage of tumor cyst fluid into subarachnoid spaces, in order to prevent chemical meningitis. The pituitary stalk is visualized during removal of posterior part of tumor [Figure 2]f and every effort was made to preserve this, by avoiding suction, CUSA or bipolar coagulation near stalk.
The most common pathology in this series was craniopharyngioma [Figure 3] and [Figure 4] in 25 patients (52%) followed by meningiomas in eight patients, hypothalamic and chiasmal gliomas in four patients each, while epidermoid and giant pituitary adenomas were present in three patients each [Table 3].
Among the 25 patients with craniopharyngiomas, radical resection was achieved in 22 (88%) patients, while subtotal resection was done in 3 (12%) patients. Of the 8 patients with meningiomas, total resection of was achieved in 6 patients. All the patients with epidermoid and pituitary adenomas underwent gross total resection of the lesions. In patients with hypothalamic/chiasmal gliomas, only subtotal resection was performed.
Complications
High morbidity (mostly transient) can be explained by radical approach adopted by the surgeon in resecting these lesions. Postoperative endocrine function Post operatively, 19 (40%) patients were found to have hypopituitarism and required hormonal replacement therapy. In rest of the patients, assessment of hypothalamo-pituitary axis revealed normal results. Postoperative visual functions Among the 33 patients with preoperative visual deficits, 23 (70%) patients had improvement in visual functions. Overall, the visual function either remained unchanged or improved in 44 (91.7%) patients, while four (8.3%) patients had deterioration in vision. None of the patients with normal preoperative vision had visual deterioration after surgery.
Anterior interhemispheric approach has been described by various authors for treatment of suprasellar lesions. [1],[2],[4],[5],[6] The advantages of this approach are that it provides a wider corridor with excellent visualization of anterior circulation, optic apparatus, and tumor within the third ventricle itself. However, there is a risk of rupture of anterior draining veins with consequent venous infarct of supero-medial frontal lobes bilaterally especially when combined with prolonged frontal lobe retraction. A basal interhemispheric approach has been described by Shibuya et al. [6] and Shirane et al. [8] for craniopharyngiomas and by Yasui et al. for anterior communicating artery aneurysms. [9] The advantage of this approach lies in the fact that it requires minimal brain retraction, allows preservation of arteries and veins along the medial and dorsal surfaces of frontal lobes and corpus callosum and involves less extensive dissection of interhemispheric fissure, limited only to basal part. Additionally, basal approach offers a much acute angle for a better visualization of third ventricular tumor and area behind lamina terminalis to as far behind the aqueduct and basilar apex, as opposed to standard interhemispheric or pterional approach combined with translamina terminalis approach. [6],[8],[10],[11] As the posterosuperior part of tumor is not adherent to adjacent structures, corridor provided by basal interhemispheric approach is adequate to remove this portion of tumor without damaging third ventricular floor and veins in the region. [11],[12],[13],[14] The bilateral midline approaches provide a true midline perspective, better orientation under operative field, view of tumor from different angles avoiding blunt dissection and permitting complete and safe excision, [6],[8],[10],[11] unlike the unilateral approaches (like pterional approach, subtemporal approach) for suprasellar lesions located in midline such as craniopharyngiomas, hypothalamic glioma and midline anterior circulation aneurysms. The bilateral approaches provide a wide uninterrupted view of important midline structures, such as optic chiasm, anterior communicating artery with perforators, hypothalamus and infundibulohypophyseal axis, thereby, providing a better chance to preserve these important anatomic structures. The contralateral structures are relatively blind for unilateral approaches and important perforators on ipsilateral side prevent a safe approach. However, there are certain situations in which BBIA cannot be used. Presence of active sinusitis involving frontal sinuses is an absolute contraindication to this approach. Additionally, tumors with extension into middle cranial fossa cannot be completely removed by this approach. Although the pterional approach is familiar to the neurosurgeons, ipsilateral optic nerve obstructs vision and dissection, thereby making the removal of tumor medial to optic nerve difficult and also third ventricle is visualized obliquely through the lamina terminalis. The subfrontal approach [15],[16] is another unilateral approach that has been widely used for lesions in this location due to its simplicity and also because it obviates the need to dissect open the interhemispheric fissure. However, an important drawback of this approach is its relatively narrow corridor as compared with interhemispheric approach. It is difficult to open the entire lamina terminalis with this approach, thereby requiring extreme retraction of frontal lobes. It also does not give a midline orientation of regional anatomy as described above. As tumors in suprasellar location have a close relationship with infundibulohypophyseal axis, and may even be densely adherent to infundibulum, meticulous dissection and preservation of infundibulohypophyseal axis constitutes an important aspect of surgery in this region. The fronto-basal interhemispheric approach offers a good chance to achieve this goal as it provides a good view of infundibulohypophyseal axis. In addition, it does not require strong retraction of frontal lobes if lamina terminalis is widely exposed. [8] Shirane et al. [8] used a small craniotomy to prevent inadvertent damage to olfactory tracts, fornix, corpus callosum, and anterior commissure. In their series of 31 patients, none of the patients developed olfactory dysfunction or psychological problems and only one patient developed transient ischemic damage to hypothalamus. When compared to classical interhemispheric approach, BBIA provides angle of visualization from base so that 3 rd ventricle and superior surface of tumor are well visualized because of inferior angle, needs no coagulation of bridging veins, permits improved pituitary stalk preservation and hormonal outcome, thereby postoperative course is less stormy. Retraction of bilateral frontal lobes and contusion and contamination from opening of frontal sinuses are potential drawbacks of this approach; however, in our series only one patient (2.2%) developed frontal lobe retraction secondary to retraction. A comparison between merits and demerits of different approaches to suprasellar tumors are given in [Table 5].
Shirane et al. [8] achieved total resection in 71% patients with craniopharyngiomas using frontobasal interhemispheric approach. Hypothalamo-pituitary dysfunction was observed in 81% of the patients. They reported a mortality rate of 7.1% (3/42). Similarly, Shibuya et al. [6] performed total or near total resection of craniopharyngiomas in 22 patients via BBIA. Visual deterioration was seen in two of the patients (9%). All except one of their patients required hormone replacement. There were three deaths (13.6%) in a delayed manner. Hori et al. [10] accomplished total resection in 80.4% of patients using anterior interhemispheric approach; however, the rate of postoperative hypothalamic dysfunction and dyselectrolytemia was very high. Diabetes insipidus occurred in 62.2% of patients after surgery. Visual deterioration occurred in 10.7% patients. Fahlbusch et al. [1] reported 45.7% total resection rates for craniopharyngiomas operated by pterional and anterior interhemispheric approach. The risk of visual deterioration in their patients operated transcranially was 14.7%. Yasargil et al. [16] adopted a very aggressive approach toward craniopharyngiomas in their series of 144 patients and achieved total resection in 90% of patients. They reported a mortality rate of 16.7%. They also reported a very high incidence of postoperative hypothalamic dysfunction in 79% of patients. In the present series, radical resection was achieved in 21/25 (84%) of the patients with craniopharyngiomas. Six of the eight patients (75%) with meningiomas underwent total resection diabetes insipidus was seen in 15 (33%) patients and hormonal disturbances requiring replacement therapy were seen in 19 (40%) patients postoperatively. Visual deterioration occurred in 4 (8.3%) patients. The mortality rate was 6.2% (3/48). The extent of resection and complication rate was comparable to those reported in literature.
[Figure 1], [Figure 2], [Figure 3], [Figure 4]
[Table 1], [Table 2], [Table 3], [Table 4], [Table 5]
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