Anatomic-Clinical Substantiation of the Contralateral Pterional Approach in Surgery of Aneurysms of the Willis Circle Anterior Segment

Krylov V.V., Tkachyov V.V., Dobrovolsky G.F.

Sklifosovsky Research Institute of Emergency Care, Moscow, Russia

Introduction

A choice of an optimum surgical approach is one of the main pledges of successful operations for intracranial aneurysms. It is determined by a number and localization of aneurysms, involvement of vessels of one or several vascular regions, intensity of basal subarachnoid hemorrhage, hematoma presence and its localization, spread of vascular spasm, a degree of cerebral ischemia, severity of a patient's state, technical equipment of an operating room and experience of a surgeon.

The latest achievements of vascular neurosurgery are greatly dependent on improvement of microsurgical technique and development of new surgical approaches to basal vessels. There are two trends of approaches evolution. The first is development and introduction of extended craniobasal approaches for surgery of difficult-of-access aneurysms of the vertebrobasilar region, giant aneurysms, aneurysms in an acute period of subarachnoid hemorrhage with a complicated course. The second is creation of less traumatic (the so-called limited) approaches for surgical treatment of patients with aneurysms in cold or acute periods of hemorrhage, an uncomplicated course and a satisfactory state.

One of surgical approaches, providing better possibilities in treating patients with aneurysms of basal vessels, is the contralateral pterional approach. We regard it as a surgical approach to brain injuries of different etiology with use of frontotemporal-sphenoidal craniotomy on the side, opposite to a damage focus.

Yasargil M.G. was the first to demonstrate possible exclusion of aneurysm of the contralateral hemisphere from blood flow. It happened in 1977, when he used the pterional approach for clipping bilateral ophthalmic aneurysms [16].

The contralateral pterional approach is applied more often (a) in single and bilateral aneurysms of the ophthalmic segment of the internal carotid artery (ICA) [1, 3, 4, 5, 7, 8, 9, 12, 14, 15], and (b) multiple bilateral aneurysms of other localization (the so-called unilateral approach) with the purpose of one-stage clipping of all aneurysms, including those located in different vascular regions [2, 6, 10, 13, 15].

The authors are unanimous in their opinion, that it is expedient to use the contralateral approach for exclusion of small aneurysms of the ICA ophthalmic segment with a cupola, directed medially. According to Fries G. et al. [3] and Vajda J. et al. [15] the contralateral approach can be more effective than the ipsilateral approach in case of large ophthalmic aneurysms, whose cupola is directed medially and which displace the ophthamic nerve laterally.

However, this opinion is not shared by all neurosurgeons. Dolene V.V., commenting upon the article by Fries G. et al. [3], emphasizes, that use of the contralateral approach in all cases with single ophthalmic aneurysms is inexpedient. As for bilateral carotid-ophthalmic aneurysms, Dolene V.V. considers clipping of small aneurysm via the contralateral access to be possible, when it is approached from the side of larger aneurysm. Yasargil M.G., who gives preference to the ipsilateral approach, reports exclusion of bilateral ophthalmic aneurysms in 7 cases, using the unilateral access.

Perneczky A. et al. [11] used the contralateral pterional approach for clipping of not only carotid-ophthalmic aneurysms, but also aneurysms, localized below the anterior clinoid process and including those of the ICA cavernous segment. Contralateral surgery of aneurysms of the ICA ophthalmic (C2) and clinoid (C3) segments, as well as a proximal horizontal part of the cavernous segment (C4), were studied experimentally and then demonstrated under clinical conditions by Sheikh B. et al. [12].

Yasargil M.G. [17], Vajda J. et al. [15], Lynch J.C. et al. [6], De Oliveira E. et al. [2], Oshiro E.M. et al. [10] used the contralateral approach in surgery of multiple bilateral aneurysms. They proved possibility of clipping aneurysms of the posterior communicating artery (PCoA), anterior choroidal artery, bifurcation of the contralateral ICA (cICA), the M1 segment and bifurcation of the contralateral middle cerebral artery (cMCA).

While selecting patients for contralateral surgery of aneurysms, the majority of the authors gave preference to cases in a compensated state (the I-II degree according to Hunt-Hess Scale). Lynch J.C. et al. [6] and Oshiro E.M. et al. [10] reported, that severity of brain edema did not allow to perform an intervention on aneurysm of the conralateral carotid region in some patients with bilateral aneurysms and the III degree of a state severity (Hunt-Hess Scale).

A problem of the contralateral pterional approach in surgery of intracranial aneurysms is still open. Reports, devoted to its use are rather scanty. The majority of them are limited to description of separate clinical cases. Some articles describe microsurgical anatomy of this approach and analyze series of clinical cases. Possible use of the contralateral approach in aneurysm surgery is estimated by this or that author in a different way. There are no precise indications and contraindications for applying this approach. Thus, study of this problem seems to be important.

The study goal

Is to analyze data of topographic-anatomic investigation of the contralateral pterional approach and results of its clinical application and to give anatomic-clinical substantiation of its use in surgery of cerebral aneurysms.

Material and Methods

We used 22 preparations, being blocks, which can be defined as "brain-skull base-vertebral spine". They were prepared according to special methods and studied on both sides. There were 5 preparations of the "head-neck" type. A method of stage-by-stage micropreparation was used for studying 7 blocks. Modeling of the pterional approach to cICA and cMCA was carried out on both sides of 15 blocks. It was followed by stage-by-stage micropreparation, morphometry of neural and vascular formations. Preparations of the "head-neck" type were used for working through 4 versions of pterional craniotomy, ensuring the contralateral approach to cICA and cMCA.

The results of surgical treatment of 34 patients with aneurysms of basal vessels were analyzed. They were operated in the Department of Emergency Neurosurgery of the Sklifosovsky Research Institute of Emergency Care. The contralateral pterional approach was used during operations. The age of patients varied from 15 up to 71 years. There were 10 males and 24 females. On admission total cerebral angiography was carried out in all cases; CT of the brain and MRI-examination in a vascular mode were used in 28 and 2 cases respectively. One, two, three and four aneurysms were diagnosed in 12, 13, 7 and 2 patients respectively (a total number of aneurysms in 34 cases was equal to 67). Subarachnoid hemorrhage was watched in 28 cases, 5 patients had repeated hemorrhages. A pseudotumorous course of the disease was observed in one patient with giant aneurysm of the ICA bifurcation. Aneurysm rupture in cases with multiple aneurysms was diagnosed on the basis of CT, angiography, EEG findings and clinical signs. Multiple aneurysms were combined with arteriovenous malformation of the occipital lobe in one patient; AVM was not resected.

Operations in an early hemorrhagic period, i.e. within the first 14 days after aneurysm rupture or repeated hemorrhage, and two weeks after it, were performed in 11 and 22 patients respectively. Left- and right-sided approaches were applied respectively in 6 and 28 cases.

A state severity, estimated before an operation on the basis of Hunt-Hess Scale, was as follows: the I degree - 8 patients, the II degree - 18 patients, the III degree - 7 patients and the IV degree - 1 patient. Functional outcomes of surgical treatment were assessed in accordance with Glasgow Coma Scale.

Statistical analysis of obtained results was carried out with the help of Statistica v5.5a program. Descriptive statistics, Spearman index of rank correlation (R), Mann-Witney (U) and Cruskall-Wallis (H) criteria were used.

Results

The contralateral pterional approach consists of 4 main stages:

  1. craniotomy,
  2. the frontobasal approach to the median line,
  3. the microsurgical approach to neurovascular formations of the contralateral hemisphere,
  4. closure of an operative wound.

 

I. Craniotomy (the First Stage)

This approach is performed in a supine position of a patient with his head, tilted (30o) opposite the side of craniotomy. The trunk is rotated (30o) to the same side too. Besides, the head is tilted back (10-15o). We studied four versions of pterional craniotomy, used in the contralateral approach (fig.1):

  1. The mini-approach (limited frontotemporal-sphenoidal craniotomy with applying a crown-shaped cutter of 30 mm in diameter);
  2. The standard approach (standard frontotemporal-sphenoidal craniotomy);
  3. The extended approach (frontotemporal-sphenoidal craniotomy, extended in the direction of the median line);
  4. The cranio-orbital approach (orbital-frontoparietal-sphenoidal craniotomy).

The craniotomy technique was worked through on both sides of 5 preparations of the "head-neck" type. Quantitative parameters of an operative wound (its depth, angles of operative activity in horizontal and vertical planes) were studied on both sides of 10 blocks while approaching four "targets": the anterior communicating artery (ACoA), opening of the ophthalmic artery of cICA, bifurcations of cICA and cMCA.

Results of morphometry (medians, lower 25% and upper 75% quartiles of quantitative parameters) are given in table 1.

Table 1

Quantitative Parameters of the Contralateral Approach

A target ®

ACoA

Opening of the ophthalmic artery of cICA

Bifurcation of cICA

Bifurcation of cMCA

Craniotomy ¯

1

2

3

1

2

3

1

2

3

1

2

3

The mini-approach

46.5
42.3
49.3

25.5
25.0
28.5

23.0
22.0
25.0

51.1
47.2
57.6

23.0
22.0
25.5

21.0
19.5
22.0

58.5
55.4
64.4

20.0
19.5
22.0

18.0
16.5
20.0

72.0
67.5
80.3

16.0
14.0
18.5

14.5
12.5
16.0

The standard approach

46.5
42.3
49.3

59.0
54.5
64.0

30.0
29.0
34.5

51.1
47.2
57.6

52.5
47.5
58.0

28.5
27.0
32.0

58.5
55.4
64.4

45.0
41.0
49.0

25.0
22.5
28.0

72.0
67.5
80.3

38.5
35.0
41.0

21.0
20.0
24.5

The extended approach

46.2
44.2
48.6

76.0
72.0
79.5

30.0
29.0
34.5

48.7
46.6
53.9

70.0
65.5
73.5

28.5
27.0
32.0

59.9
55.4
64.4

60.0
58.0
65.0

25.0
22.5
28.0

70.7
67.5
80.3

50.0
48.0
55.0

21.0
20.0
24.5

The cranio-orbital approach

46.2
44.2
48.6

76.0
72.0
79.5

36.0
35.0
41.0

48.7
46.6
53.9

70.0
65.5
73.5

34.0
33.0
38.0

59.9
55.4
62.4

60.0
58.0
65.0

30.5
27.5
34.5

70.7
67.5
80.3

50.0
48.0
55.0

26.0
23.0
29.0

Note: 1 - a wound depth (mm); 2 - angles of operative activity in a horizontal plane; 3 - angles of operative activity in a vertical plane (degrees).

 

II. The Frontobasal Approach to the Median Line (the Second Stage)

This stage is a standard procedure in surgery of the brain base aneurysms, used, for example, in approaching ACoA aneurysms [17]. Carotid, chiasmal and interpeduncular cisterns are dissected on the side of craniotomy. The cistern of the lateral fissure is dissected widely. ICA, the M1 segment of MCA, the A1 segment of the anterior cerebral artery (ACA), both optic nerves and chiasm are exposed. Perforation of the terminal plate of the third ventricle is performed with the purpose of retraction pressure reduction; liquor is aspirated from the ventricular system. Structures of the contralateral hemisphere are approached through a space, limited by the falciform process at the front, the terminal plate of the third ventricle and chiasm at the back, a basal surface of the frontal lobe from above and the anterior cranial fossa base from below.

 

III. The Contralateral Approach Proper (the Third Stage)

One can use several microsurgical corridors for approaching aneurysms of the contralateral hemisphere (fig.2). Our topographic-anatomic study allowed to identify the following microsurgical corridors: interoptic (a), contralateral transbasal (b), contralateral opticocarotid (c), contralateral retrocarotid (lateral) (d), contralateral supracarotid (e) and contralateral transsylvian (f).

A) An Interoptic Corridor. It has a triangular shape. The "triangle" apex is the chiasm, its sides are optic nerves and its base is limbus sphenoidalis. Entry to the interoptic corridor is closed by the arachnoid plate, forming an anterior wall of the chiasmal cistern. Its dissection and opening of the cICA carotid cistern allows to visualize the following structures (fig.3):

When the contralateral approach is applied, a surgeon can enlarge an interoptic space and extend a zone of access by mobilizing both optic nerves, dissecting a membranous part of the optic nerve canals or achieving transposition of the optic nerves, using a transbasal corridor.

B) A Contralateral Transbasal Corridor. We regard a contralateral transbasal corridor as a space, which appears after dissection of meningeal and bone structures of the skull base. It is achieved by resection of the saddle tubercle and a fragment of planum sphenoidale, removal of a superior wall of the optic nerve canal, optic support (inferior and medial walls of the optic canal) and medial segments of the anterior clinoid process on the side opposite to the approach. These manipulations result in possibility of mobilizing the contralateral optic nerve at a considerable length, visualizing anterior and medial surfaces of the clinoid segment (C3), the proximal and distal dural ring, distal parts of the cICA horizontal segment (C4) and exercising direct proximal control of the C2 segment.

) A Contralateral Opticocarotid Corridor.This corridor is traditionally regarded as a triangular space, limited by the contralateral optic nerve and chiasm medially, the contralateral ICA laterally and the A1 segment of the contralateral ACA from above (fig.4). Manipulations in the opticocarotid corridor of the contralateral hemisphere can be started after dissection of the chiasmal and carotid cisterns on the opposite side. The following structures are visualized through the opticocarotid space:

D) A Contralateral Retrocarotid (Lateral) Corridor. This corridor is viewed by us as a chink-like space, limited by the contralateral optic nerve medially and from below, the anterior clinoid process and cerebellum tentorium laterally and from below, a medial surface of the temporal lobe and the M1 segment of cMCA from above. Dissection of the carotid cistern allows to visualize the following structures:

E) A Contralateral Supracarotid Corridor. We regard this corridor as a triangular space, limited by the A1 segment of the contralateral ACA (cACA) medially and from below, the M1 segment of cMCA laterally and from below, the anterior perforated substance from above. This space is accessible after dissection of the carotid cistern, the terminal plate cistern and initial segments of the lateral fissure cistern of the contralateral hemisphere. It results in visualization of (fig.4):

F) A Contralateral Transsylvian Corridor. According to our conception, this corridor is a chink-like space; its anterosuperior and posteroinferior walls are represented by a mediobasal surface of the contralateral frontal lobe and a mediobasal surface of the temporal lobe respectively; it is limited by the arachnoid, forming the lateral fissure cistern of the contralateral hemisphere, medially and from below. Entry to this corridor is achieved by dissection of the lateral fissure cistern of the contralateral hemisphere. After it one can visualize (fig.5):

Modeling of the pterional approach was carried out by us on both sides of 15 blocks (30 observations), mentioned above. Morphometry was used for estimation of main neurovascular formations (dimensions of an interoptic space, a length of the ICA, ACA and MCA segments, diameters of basilar arteries, etc.). Origin of openings of perforating arteries and accessibility of cICA and cMCA segments were studied.

Adequate visualization of anterior and medial surfaces of the cICA clinoid segment was typical of all instances. As for the ophthalmic, communicating and choroidal segments of cICA and its bifurcation, they were visualized in 24 (80%), 21 (70%), 30 (100%) and 26 (87%) observations respectively. Visualization of the M1 segment and bifurcation of cMCA became possible in 18 (60%) out of 30 observations.

 

IV. Closure of an Operative Wound (the Fourth Stage)

This stage has no peculiarities in the contralateral approach.

Results of Contralateral Surgery of Aneurysms

Operations were performed with application of the OPMI 6 OPTON operating microscope (magnification of 8-16 times) and microsurgical instruments. Standard or extended (in the direction of the median line) frontotemporal-sphenoidal craniotomy was used. Arteries of the contralateral hemisphere were approached through the above microsurgical corridors after the arachnoid dissection on the side, ipsilateral to the approach, perforation of the terminal plate of the third ventricle and achievement of good relaxation of the brain.

Results of Treatment of Patients with Aneurysms of the cICA Ophthalmic Segment

The contralateral approach was used in 14 patients with 15 aneurysms of the cICA ophthalmic segment. Single and multiple aneurysms were watched in 7 and 7 cases respectively. The total number of aneurysms in 14 patients was equal to 24. There was one giant aneurysm; big aneurysms were present in 2 cases; one patient had 2 aneurysms of the cICA ophthalmic segment (table 2). The cupola direction was as follows: superlateral - 7 cases, superior - 3 cases, medial - 3 cases, inferiolateral - 1 case. Aneurysms were clipped in 14 patients; one aneurysm was coated with a muscular graft. Right- and left-sided approaches were applied in 11 and 3 cases respectively. Intracerebral hematomas of mediobasal segments of the contralateral frontal lobes were removed in 2 patients (15 cm3 and 40 cm3 respectively). Preventive exposure of the common carotid artery on the neck was performed in 4 cases with the purpose of proximal control. Intraoperative bleeding in operations on contralateral ophthalmic aneurysms took place in 3 patients. Postoperative vision disorders developed in 8 patients; they were caused by traction of the optic nerve in 7 of them. Unilateral amaurosis and considerable reduction of vision acuity were watched in 5 and 2 patients respectively. The aneurysm cupola had superlateral and superior direction in 5 and 2 cases of this group respectively. Right-sided nasal hemianopsia developed in 1 patient. Complete restoration of working ability and social rehabilitation were achieved in 5 out of 8 cases with vision disorders; due to this fact, their functional outcomes were referred to the I degree according to Glasgow Coma Scale. Postoperative persistent neurologic deficit, manifesting itself in the form of sensomotor aphasia and right-sided hemiparesis, was typical of 1 patient. It was caused by vascular spasm and cerebral ischemia. Outcomes of surgical treatment were as follows (Glasgow Coma Scale): the 1 degree - 9 patients, the II degree - 4 patients, the III degree - 1 patient. There were no fatal outcomes.

Results of Treatment of Patients with Aneurysms of the cICA Communicating and Choroidal Segments

The contralateral approach was used in 6 patients with 4 and 2 aneurysms of the cICA communicating and choroidal segments respectively. Five aneurysms were clipped; one aneurysm was coated with a muscular graft. Right- and left-sided approaches were applied in 5 and 1 cases respectively. The contralateral aneurysm exposure was accompanied by intraoperative bleeding in one patient. Outcomes of surgical treatment were as follows (Glasgow Coma Scale): the I and II degrees were watched in 2 cases; 4 patients died. Only one fatal outcome was caused by the applied approach. The patient died of repeated hemorrhage from the left ICA-PCoA due to incomplete clipping by means of the contralateral approach.

Surgical Treatment of Aneurysms of the cICA Bifurcation and Its Results

The contralateral approach was used in 3 patients with aneurysms of the cICA bifurcation. All aneurysms were single. They were giant in 2 patients; a pseudotomorous course of the disease was watched in one of them (there was no aneurysm rupture). One more patient had big aneurysm. All aneurysms were clipped; right- and lest-sided approaches were applied in 2 and 1 cases respectively. Intraoperative bleeding was watched in one patient during exposure and clipping of contralateral aneurysms of the ICA bifurcation. Outcomes of surgical treatment were as follows (Glasgow Coma Scale): the 1 degree - 1 male patient, the II degree - 1 female patient. One female died on the 26th day after the operation. Fatal outcome was caused by recurrent thromboembolism of the pulmonary artery and brain infarction due to vascular spasm.

Aneurysms of the M1 Segment and Bifurcation of cMCA and Results of Their Surgical Treatment

The contralateral approach was used in 11 patients with 12 aneurysms of the M1 segment and bifurcation of cMCA. Single and multiple aneurysms were watched in 2 and 9 patients respectively. Right- and left-sided approaches were performed in 10 and 1 cases respectively. Both single aneurysms of cMCA were big, their body and cupola had inferior localization. Use of the ipsilateral pterional approach in aneurysm of this shape assumes contacting its cupola and body before exposure of the MCA trunk. It results in a greater risk of intraoperative bleeding and impossibility of preventive clipping of the artery. Thus, preference was given to the contralateral approach. Both single aneurysms were clipped. As for 9 patients with mulptiple aneurysms, one of them had 2 aneurysms of the cMCA M1 segment and bifurcation, which were clipped; two cases had small aneurysms. They were coated with a muscular graft. Aneurysms of cMCA in the rest 6 patients were clipped; a paracervical part of one clipped aneurysm was coated with a muscular graft. There were no intraoperative hemorrhages during exposure and clipping of contralateral aneurysms of the cMCA M1 segment and its bifurcation. Outcomes of surgical treatment were as follows (Glasgow Coma Scale): the 1 degree - 7 patients, the II degree - 2 patients. There were 2 fatal outcomes. Both patients (the V degree) died of brain infarction, caused by vascular spasm.

The Contralateral Approach and Outcomes of Surgical Treatment of Patients with Single and Multiple Cerebral Aneurysms

There were 34 patients; 7 of them died. Postoperative neurologic disorders were watched in 13 cases; 9 of them had different vision disturbances. Improvement or absence of augmentation of neurologic symptoms were typical of 14 patients. Intraoperative bleeding took place in 6 cases (17.6%); 5 of them (14.7%) developed during exposure of contralateral aneurysms. Glasgow Coma Scale was used for estimation of treatment results. They were as follows: the I degree - 18 patients, the II degree - 8 patients, the III degree - 1 patient, the V degree - 7 cases (table 2).

Table 2

Contralateral Surgery of Aneurysms and Its Results

Number of Aneu-rysms

A State before Operation (Hunt-Hess Scale)

A Period between Operation and Hemorrhage

Vascular Regions Prepared during Operation

A Postoperative State (Glasgow Coma Scale)

 

I

II

III

IV

V

Up to 2 weeks

More than 2 weeks

Two

Three

I

II

III

IV

V

1

2

7/1

3

-

-

5/1

6

12/1

-

7

4

-

-

1

2

5

5/1

2/1

1/1

-

5/3

8

12/2

1/1

7

2

1

-

3

3

1

5/1

1

-

-

-

7/1

5

2/1

4

2

-

-

1

4

-

2/2

-

-

-

1/1

1/1

-

2/2

-

-

-

-

2

Note: Fractions indicate a number of fatal outcomes in each group.

Discussion

Our topographic- anatomic studies show, that an angle of operative activity in a horizontal plane of the minipterional approach is 2 times smaller, than that of the standard pterional approach and 3 times smaller, than those of the extended frontotemporal-sphenoidal craniotomy and orbitoptreional approach. An angle of operative activity in a frontal plane of the minipterional approach is 1.3 times smaller, than those of the standard pterional approach and extended frontotemporal-sphenoidal craniotomy and 1.5 times smaller, than that of the orbitopterional approach. Difference in an operative wound depth, watched in different versions of craniotomy, is statistically insignificant.

The contralateral approach allows to visualize:

It is difficult to visualize the following structures:

Possibility of visualization of structures of the contralateral hemisphere is determined chiefly by individual peculiarities of microanatomy of each case (dimensions of an interoptic space, a length of ICA and its separate segments, localization of openings of the ophthalmic artery, PCoA, STA, a length of the M1 segment).

The statistical analysis of the results of anatomic modeling was indicative of statistically significant correlation between:

The dispersion analysis demonstrated statistically reliable difference of groups with various accessibility of the cMCA bifurcation, depending on a length of the M1 segment (H=14.86754, p=0.006). The median in cases with the accessible M1 segment was 13.65 mm; 25% and 75% quartiles were equal to 12.5 mm and 15.1 mm respectively. The median, 25% and 75% quartiles in cases with limited accessibility of the M1 segment were 17.5 mm, 17.0 mm and 19.5 mm respectively. When the M1 segment was inaccessible, the median, 25% and 75% quartiles were equal to 24.2 mm, 19.4 mm and 27.5 mm respectively.

The statistical analysis of results of surgical treatment with applying the contralateral pterional approach was indicative of statistically significant correlation, which was as follows:

The dispersion analysis showed:

Conclusion

The obtained results make it possible to conclude, that optimum conditions for the contralateral approach include use of pterional craniotomy, extended in the direction of the median line, or the orbitopterional approach, which allow to enlarge an angle of operative activity and to improve polypositional visualization of vascular structures of the contralateral hemisphere. Possibilities of "miniapproaches" in performing the contralateral approach are extremely limited.

The contralateral approach is a method of choice in case of (a) aneurysms of the ophthalmic cICA segment, when their cupola has inferior, inferiomedial and medial directions; (b) aneurysms of the cICA choroidal segment and its bifurcation; (c) aneurysms of the M1 segment and bifurcation of cMCA (if a length of the M1 segment does not exceed 15-19 mm); (d) its use as a unilateral approach in surgery of multiple aneurysms. In case of aneurysms of the cICA communicating segment, a problem of their possible clipping can be often solved only intraoperatively. It is expedient to perform transposition of the optic nerve in contralateral surgery of ophthalmic aneurysms, whose cupola is characterized by superior and superlateral directions. When the contralateral approach is planned, it is necessary to take into consideration individual peculiarities of aneurysm (its size, localization of its neck and a cupola direction).

While selecting cases for contralateral surgery, one should give preference to patients in a compensated state (the I-III degree according to Hunt-Hess Scale). If there are multiple aneurysms, operation should be limited to clipping of aneurysms of not more, than two vascular regions.

REFERENCES

  1. De Jesus O., Sekhar L.N., Riedel C.J. Clinoid and paraclinoid aneurysms: surgical anatomy, operative techniques, and outcome. Surg. Neurol. 1999. May; 51(5):477-488.
  2. de Oliveira E., Tedeschi H., Siqueira M.G. et all. Anatomical and technical aspects of the contralateral approach for multiple aneurysms. Acta Neurochir. (Wien) 1996; 138(1):1-11;
  3. Fries G., Perneczky A., van Lindert E., et all. Contralateral and ipsilateral microsurgical approaches to carotid-ophthalmic aneurysms. Neurosurg. 1997 Aug.;41 (2):333-343.
  4. Kakizawa Y., Tanaka Y., Orz Y. Parameters for Contralateral approach to ophthalmic segment aneurysms of the internal carotid artery. Neurosurg., Vol. 47, 5, Nov. 2000, . 1130-1137.
  5. Kato Y., Sano H., Hayakawa M. et all. Surgical treatment of internal carotid siphon aneurysms. Neurol. Res. 1996 Oct.;18(5):409-415.
  6. Lynch J.C., Andrade R. Unilateral pterional approach to bilateral cerebral aneurysms. Surg. Neurol. 1993 Feb.; 39(2):120-127.
  7. Milenkovic Z., Gopic H., Antovic P., Jovicic V., Petrovic B. Contralateral pterional approach to a carotid-ophthalmic aneurysm ruptured at surgery. Case report. J. Neurosurg. 1982 Dec.;57(6):823-825.
  8. Nakao S., Kikuchi H., Takahashi N. Successful clipping of carotid-ophthalmic aneurysms through a contralateral pterional approach. J. Neurosurg. 1981 Apr.;54(4):532-536.
  9. Nishio S., Matsushima T., Fukui M., Sawada K., Kitamura K. Microsurgical anatomy around the origin of the ophthalmic artery with reference to contralateral pterional surgical approach to the carotid-ophthalmic aneurysm. Acta Neurochir. (Wien) 1985;76(3-4):82-89.
  10. Oshiro E.M., Rini D.A., Tamargo R.J. Contralateral approaches to bilateral cerebral aneurysms: a microsurgical anatomical study. J. Neurosurg. 1997. Aug.;87(2):163-169.
  11. Perneczky A., Knosp E., Vorkapic P., Czech T. Direct surgical approach to infraclinoidal aneurysms. Acta Neurochir. (Wien) 1985;76(1-2):36-44.
  12. Sheikh B., Ohata K., El-Naggar A. et all. Contralateral Approach to Junctional C2-C3 and Proximal C4 Aneurysms of the Internal Carotid Artery: Microsurgical Anatomic Study. Neurosurgery 2000 May, Vol. 46(5).- P. 1156-1161.
  13. Shibata S., Tsutsumi K., Mori K. Surgical management of an internal carotid lesion by contralateral pterional approach in bilateral intracranial aneurysms: report of two cases. No Shinkei Geka. 1985 Jul.;13(7):779-782.
  14. Shiokawa Y., Aoki N., Saito I., Mizutani H. Combined contralateral pterional and interhemispheric approach to a subchiasmal carotid-ophthalmic aneurysm. Acta Neurochir. (Wien) 1988;93(3-4):154-158.
  15. Vajda J., Juhasz J., Pasztor E., Nyary I. Contralateral approach to bilateral and ophthalmic aneurysms. Neurosurgery. - 1988 Apr.;22(4):662-668.
  16. Yasargil M.G., Casser J.C., Hodoch R.M. et all. Carotid-ophthalmic aneurysims: direct microsurgical approach. Surg. Neurol. I977. 8: 155-165.
  17. Yasargil M.G. Microneurosurgery. Vol.1-2. Georg Thieme Verlag. Stuttgart.New York.1984.