Lamina terminalis approach for retrochiasmal craniopharyngiomas

Invited papers 9 Springer-Verlag 1990 Child's Nerv Syst (1990) 6:425 429

Lamina terminalis approach for retrochiasmal craniopharyngiomas Sanat N. Bhagwati, Chandrashekhar E. Deopujari, and Geeta D. Parulekar Department of Neurosurgery, Medical Research Centre, Bombay Hospital, 12 Marine Lines, Bombay - 400020, India Received August 21, 1989/Revised January 15, 1990

Abstract. The retrochiasmal location of a tumour and the presence of a prefixed chiasm pose a major difficulty in total excision of craniopharyngiomas. An approach through the lamina terminalis gives direct access to these lesions, which are situated predominantly in the midline. Our experience with total excision of six such tumours exclusively through the lamina terminalis route is presented. Despite a stormy postoperative course due to water and electrolyte imbalance, no mortality resulted and minimal long-term morbidity was observed. Total excision was confirmed in all the cases by postoperative computed t o m o g r a p h y scans.

available. Opticocarotid or subtemporal approaches are utilized in these cases, but are likely to be inadequate to deal with a retrochiasmal lesion that is predominantly in the midline. Alternatively, transpetrosal-transtentorial or transcranial-transsphenoidal approaches may be used, but they involve an extensive exposure with its inherent risks. We have used an approach through the lamina terminalis to achieve total excision of retrochiasmally located craniopharyngiomas with prefixed chiasm. We find this approach to be simple and safe in carrying out total excision of retrochiasmal tumours.

Key words: Craniopharyngioma - Retrochiasmal tumours - Prefixed chiasm - Lamina terminalis

Patients and methods

Harvey Cushing stated in 1932 that "Craniopharyngioma offers the most baffling problem which confronts neurosurgeons" [4]. In spite of significant advances in imaging techniques, as well as surgical and endocrinological management, treatment of craniopharyngiomas remains a challenge. Halstead [8] and Lewis [17] are credited with the earliest efforts to operate on a craniopharyngioma and, though Matson carried out primary total removal in most of his cases over 30 years ago [20], it has only recently received acceptance as the ideal treatment. This has mainly been through the effrots of Sweet [29] and Hoffman [9], who have shown that a clear plane of cleavage exists around the t u m o u r and total excision can be achieved with minimal morbidity and mortality. However, the estimated primary total removal in various published series ranges from less than one-third to threequarters of the cases [1, 11, 16, 26]. One of the major problems in primary total excision is good access to a t u m o u r that has a propensity to grow in all directions. Prefixed chiasm makes access more difficult, as the usual route between the two optic nerves is not

Six patients have had total removal of craniopharyngiomas through the lamina terminalis during the last 3 years (1986-1988), The age of these patients ranged from 7 to 19 years; there were two males and four females. The details on these patients are summarized in Table 1. One remarkable clinical feature of retrochiasmal tumours is the absence of visual deficits. This was so in all our cases except one who presented with a recurrent tumour. He had had two previous operative procedures for subtotal excision and had lost vision in one eye. The absence of visual signs and symptoms (except papilloedema) can probably be used as an indicator for the clinical diagnosis of a prefixed chiasm and the predominantly retrochiasmal location of the tumour. High-definition computed tomography (CT) scan with coronal and especially sagittal reconstruction has been extremely helpful in delineating the lesion. All patients had signs of raised intracranial pressure and all, except one, had signs of hypothalamic dysfunction. One presented with retarded growth. All the cases were operated on through a unilateral frontal craniotomy up to the base and extending up to the midline. Intra k venous mannitol and drainage of the cerebral spinal fluid through basal cisterns allowed adequate frontal lobe retraction in all cases. After visualization of the optic nerves and confirming the presence of a prefixed chiasm, arachnoid over the optic nerves, the chiasm and carotid artery were divided. Anterior cerebral and communicating arteries were mobilized to allow further retraction, and self-retaining retractors were adjusted to expose the lamina terminalis. The optic chiasm is usually splayed and a bluish lamina terminalis can be visualized in the centre stretched by the underlying tumour. An incision is made strictly in the midline in the stretched lamina terminalis to avoid damage to the vascular supply of the

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426 Table 1. Details on the patients. DI, Diabetes insipidus

Case no.

Age/sex (years)

Clinical presentation

Tumour morphology

Postoperative problems

Comments

1

13/F

Solid, no hydrocephalus

2

15/M

19/F

Convulsions, aseptic meningitis, DI Convulsions, SIADH, subdural effusion, prolonged somnolence DI

Prolonged postoperative recovery, thyroid supplement Prolonged hypothalamic disturbance

3 4

7/F

Headache, vomiting, retarded growth Headache, vomiting, VI nerve paresis, obesity Headache, diplopia (VI nerve paresis) Obesity, somnolence, polydypsia, polyuria, papilloedema

5

16/M

Recurrent (operated on 1978, 1980), headache, loss of vision in one eye

Solid

6

10/F

Headache, blurred vision, papilloedema (bilateral shunts inserted)

Solid and cystic shunts

Solid and cystic, hydrocephalus Solid and cystic, unilateral hydrocephalus Solid, mild hydrocephalus

DI, myxoedema

Smooth recovery, DI controlled on carbamazepine Carbamazepine controlled DI No improvement in visual deficit

DI, visual field deficit in one eye

DDAVP, thyroid supplement

Fig. 1. Computed tomography (CT) scan showing a large retrochiasmal craniopharyngioma with calcification, solid and cystic components. Compression of foramen of Monroe has produced right lateral ventricular dilation (case 3)

optic apparatus. Biopsy of the tumour is taken and the cyst, if present, is aspirated. This gives more space to carry out further tumour removal. Gentle traction is applied to the tumour capsule to separate it from the surrounding structures. Gradually a plane is developed between the tumour and the optic nerves, chiasma and carotid arteries. A tumour from within the III ventricle can also be gently pulled out and removed. Stalk is usually sacrificed while removing the tumour in the region of the tuber cinerium and complete excision achieved. Lilequist membrane and basilar bifurcation beyond it can be visualized after excision.

Results

Total removal was achieved in all five cases of primary excision and confirmed by postoperative CT scan. It was also possible to excise the recurrent tumour completely. The latter case has the longest follow-up (3.5 years) a m o n g these patients and a recent CT scan does not show any recurrence (Fig. 8). There was no mortality a m o n g our 6 cases. The postoperative period was stormy in all the primary total excisions due to fluid and electrolyte disturbance, which need-

Fig. 2. Various approaches to craniopharyngioma. The route between the two optic nerves is not available with prefixed chiasm and a retrochiasmal tumour (modified from Carmel [3])

ed vigilant monitoring. Two patients suffered from inappropriate secretion of antidiuretic h o r m o n e (SIADH) and the other four from diabetes insipidus (DI), which is controlled with carbamazepine in three and desmopressin acetate (DDAVP) nasal drops in one. Three patients need thyroid supplements. Steroids have had to be continued for over 2 months in all of them. Although minor hypothalamic dysfunction was observed in all these cases, no major long-term disturbances were seen except for one boy who had long periods of somnolence for 2 months after surgery. Visual acuity was affected in one patient postoperatively, but it has been steadily improving. The long-standing preoperative visual deficit in the patient with recurrent turnout did not improve. Other complications included convulsions in two patients, aseptic meningitis in one, and subdural h y g r o m a with hemiparesis in one patient who showed i m p r o v e m e n t after drainage of the hygroma.

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Fig. 3. Operative photograph showing short optic nerve (prefixed chiasm) with tumour growing in midline, glistening lamina terminalis is seen in the centre Fig. 4. Operative photograph showing exposed tumour with calcification after incising lamina terminalis and partial internal decompression. Short optic nerve in front with no prechiasmatic space and anterior cerebral artery behind lamina terminalis can be well seen Fig. 5. Operative photograph showing complete excision of the tumour Fig. 6. Close up operative photograph of the operative field after total tumour excision

Discussion

Treatment of craniopharyngiomas has been controversial. However, the early results of Matson [19, 21] and the more recent experience of Sweet [29] and Hoffman et al. [11] make a strong case for primary total excision as the ideal treatment. Access to these tumours is difficult, and most intracranial approaches depend on the space between the two optic nerves. This route is not available when the tumour is retrochiasmal and the chiasm is prefixed. Various approaches have been used to deal with retrochiasmal tumours. They are: (1) opticocarotid (pterional), (2) lateral carotid (subtemporal), (3) translamina terminalis (4) transcranial-transsphenoidal, (5) transcallosal, and (6) transpetrosal-transtentorial. The lateral-carotid (subtemporal) route was successfully employed first by Guiot [6], later by others [12, 18, 23], and more recently by Symon [31] for radical excision of retrochiasmal tumours. The optico-carotid route was described by Dandy [5] and Matson [20], and has also been used by Hoffman [10] to deal with these tumours. However, visualization of the contralateral side is poor, and removal of the tumour from under the opposite optic nerve and carotid artery may be hazardous. The transcallosal-transventricular approach is good mainly for an intraventricular tumour, as the chances of hypothalamic injury are greater and visualization of the optic apparatus is poor. The transpetrosal-transtentorial approach, described by H a k u b a [7], involves an extensive exposure with its inherent risks.

The lamina terminalis approach gives good access, in most cases, to retrochiasmal craniopharyngiomas situated predominantly in the midline. Although it was mentioned by Matson [20] 30 years ago, a good account of this procedure was not widely available. Hoffman et al. [11] described in some detail the use of this approach to remove tumours with retrochiasmal extension with good results in a few cases. Sweet [30] and Konovalov [15] have also recently described their experience of this approach for total excision of craniopharyngiomas with some illustrations. Patterson and Danylevich [22] have used this route to approach craniopharyngiomas and achieved total excision in 11 cases. However, they carry out tumour removal through the sphenoid sinus, which is opened transcranially. The tumour is dissected and pushed through the lamina terminalis and then delivered through the space created in front of the chiasm. Although it is a very good procedure, especially if there is an anterior intrasellar component to the tumour, drilling the sphenoid sinus may not be necessary in most cases and carries a significant risk of infection. Suzuki [28] has also used a variation of the lamina terminalis approach through the interhemispheric route with the sacrifice of the anterior communicating artery, if necessary. We do not feel that the addition of all these manoeuvres is necessary. A low frontal unilateral craniotomy extending up to the midline or, rarely, a bifrontal craniotomy with a bone flap cut up to the base is the key to this approach. Anterior cerebral-communicating arteries can be well protected and did not suffer damage in any of our cases. The concern about damaging the optic appara-

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Fig. 7. a CT scan showing a large retrochiasmal tumour, b Postoperative CT scan showing complete excision of the lesion (case 2)

Fig. 8. a CT scan showing a large cystic and solid recurrent craniopharyngioma in retrochiasmal location, b CT scan 3 years after complete excision through lamina terminalis shows no evidence of recurrence (case 5)

tus is unfounded if the surgeon remains strictly in the 9midline while approaching the tumour through the lamina terminalis, debulks the tumour, and then gradually separates it from the optic apparatus. This is important, as the blood supply of the optic apparatus is derived from the inferior surface of the chiasm [2]. Only one of our patients had transient visual deterioration following surgery in the form of a field defect, which has nearly recovered. Hoffman et al. have also not noted significant visual problems in any of their patients, with the use of this approach [11]. Although the reported rate of tumour recurrence after total removal ranges from 9% to 26% [13, 29], Hoffman has not noted clinical evidence of recurrence if the postoperative CT scan showed no evidence of the tumour [11]. All of our six cases had postoperative CT scans, confirming total excision of the tumour. Sorva et al. have also noted clinical recurrence in only 1 of 16 cases after CT scan had confirmed total excision [27]. Hypothalamic damage seems to be the maj or concern, which makes Raimondi and Rougerie [25] and King [14] feel that an attempt at total excision of retrochiasmal craniopharyngiomas is unwarranted, as it exposes the patient to unacceptable risks. Raimondi states that total excision may be achieved in only 5 % of cases with retrochiasmat location of the tumour, and mortality could be as high as 2 0 % - 3 0 % [24]. Although all our patients had a stormy postoperative course due to hypothalamic dysfunction, there was no mortality in this small series, and diabetes insipidus has been the only long-term sequel. This is well controlled with oral carbamazepine and deamino-D-arginine vasopressin. Only one boy continued to have prolonged periods of somnolence over 2 months after surgery. Hoffman has also not noted any major morbidity with total excision, and the growth of these children and the quality of their lives has also been satisfactory in his experience [10]. In conclusion, primary total excision seems to be the ideal treatment for craniopharyngiomas, as it can be accomplished in the majority of cases with minimal morbidity and mortality. This also avoids postoperative radiotherapy with its considerable side-effects. The lamina terminalis approach adds to the possibility of total excision. With exclusive use of this approach, total excision can be achieved in retrochiasmal tumours with prefixed chiasm.

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