The subtemporal, transcavernous, anterior transpetrosal approach to the upper brain stem and clivus.

The temporal lobe, posterolateral cavernous sinus, tentorium, and petrous apex restrict anterolateral surgical access to lesions of the upper brain stem and clivus. The authors describe a modified transpetrosal approach that enhances the exposure of clival chordomas and aneurysms of the basilar artery bifurcation. An intradural and extradural subtemporal approach is combined with division of the tentorium and superior petrosal sinus, posterolateral dissection of the cavernous sinus, and intradural removal of the petrous bone from its apex to the cochlea. The indications, advantages, and disadvantages of this subtemporal, transcavernous, anterior transpetrosal approach are described in detail, along with its use in six patients.     

Brain retraction technique using gelatin sponge in the subtemporal approach

Wide exposure of lesions during the subtemporal approach often leads to temporal lobe injury caused by excessive retraction. A brain retraction technique using gelatin sponge pieces was developed to minimize intraoperative brain retraction during the subtemporal approach. After aspirating cerebrospinal fluid and slackening the temporal lobe, 2-3 pieces of gelatin sponge are inserted between the dura and surfaces of the anterior and posterior parts of the temporal lobe, then covered with cottonoids. The gelatin sponge pieces expand and thus expose the free margin of the tentorium with minimal brain retraction. This technique was used in 50 patients undergoing clipping for cerebral aneurysms. Although computed tomography indicated minor brain injury caused by retraction in three patients with ruptured aneurysm of the basilar artery bifurcation, no patients experienced new neurological deficits other than transient ipsilateral oculomotor nerve paresis. In conclusion, gelatin sponge, with its innate mechanical characteristics and ease of application, seems to offer an alternative retractor in neurosurgical interventions using the subtemporal approach for patients with unruptured aneurysm or non-severe subarachnoid hemorrhage.     

Zygomaticotemporal approach to the basis cranii and basilar artery

When using the zygomaticotemporal approach, one removes the whole of the zygomatic bone with its attachment to the masseter muscle, allowing a lower and more anterior approach to the interpeduncular cistern along the inferomedial surface of the temporal lobe. Minimal brain retraction is required to give an excellent view of the bifurcation of the basilar artery and of the suprasellar region.     

Zygomatic temporopolar approach for basilar artery aneurysms

For surgery of upper basilar artery aneurysms, we have modified the temporopolar approach proposed by Sano by detaching the zygomatic arch to obtain a wide, shallow operating field. This approach seems to be suitable for anteriorly protruding, high-positioned, or large aneurysms of the upper basilar artery. We have used this zygomatic temporopolar approach in 4 patients with such aneurysms and obtained satisfactory results. In this paper, we detail the operative procedure and emphasize certain technical points to minimize temporal lobe retraction and to prevent oculomotor and facial nerve injuries.     

A temporal transsylvian approach to anterior circulation aneurysms.

Operative management of cerebral aneurysms remains a technically challenging problem in modern neurosurgery despite major advances in microsurgical techniques. This is largely caused by the difficulty of exposing and handling these aneurysms, which are located around the circle of Willis at the base of the brain. Large cranial windows, generous brain retraction, and local brain resection have, at times, been employed to overcome these difficulties. In the present report, an exclusively temporal approach to the anterior aspect of the circle of Willis for surgical treatment of aneurysms arising from the anterior circulation is described. This approach limits the surgical preparation and the craniotomy to the temporal area, protects the temporal branch of the facial nerve from injury, and provides a superior cosmetic appearance soon after surgery. It provides a lateral transsylvian exposure to the base of the brain and thus permits the safe dissection and exposure of the aneurysms using microsurgical techniques with minimal, if any, retraction of the frontal lobe. The need for routine resection of the gyrus rectus for exposure of anterior communicating artery aneurysms is alleviated. This approach can be considered in patients harboring large or small incidental or acutely ruptured anterior circulation aneurysms. The outcome of 96 consecutive patients who underwent this procedure is described to illustrate its safety and effectiveness.     

Surgical approaches for vertebro-basilar trunk aneurysms located in the midline

Summary Fourteen cases of midline vertebro-basilar trunk aneurysms were operated on by four routes of surgical approach: middle fossa anterior transpetrosal approach (ATP), presigmoid transpetrosal approach (PTP), conventional lateral suboccipital approach (LSO) or suboccipital transcondylar approach (STC). There was no mortality, but the morbitity was different depending on the surgical approach. In basilar trunk aneurysms located higher than the internal auditory canal, excellent results were obtainable by ATP, especially in the case of posteriorly projecting aneurysms. For midline vertebral aneurysms located lower than the internal auditory canal, STC resulted in less surgical complications than LSO. Extradural resection of the jugular tubercle was necessary for aneurysms located on the distal vertebral artery at or close to the vertebro-basilar junction. For vertebro-basilar junction aneurysms located at the level of the internal auditory canal, hearing was preserved by STC, but not by ATP or PTP. However, choice of the surgical approach may depend on the direction of the aneurysm and the technical accessibility of the skull base. All these skull base approaches reduced surgical complications of retraction damage to the cranial nerves and the brain stem. This holds true for all aneurysms arising from the midline vertebro-basilar trunk.     

The extreme lateral transcondylar approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

The Extreme Lateral Transcondylar Approach to Aneurysms of the Vertebrobasilar Junction, the Vertebral Artery, and the Posterior Inferior Cerebellar Artery

The unilateral suboccipital craniotomy is the commonly performed approach to aneurysms of the vertebrobasilar junction, the vertebral artery, and the posterior inferior cerebellar artery (PICA). Many of these aneurysms are placed anterior or anterolateral to the brain stem, necessitating brain stem retraction for adequate exposure. Small dorsolateral enlargement of the foramen magnum, partial resection of the occipital condyle, and removal of the jugular tubercle allow access to the neurovascular structures ventral to the medulla without retraction of the neuroaxis. This extreme lateral transcondylar approach was performed in 20 patients with aneurysms of the vertebrobasilar junction, the vertebral artery, and the PICA; intraoperatively, two suspected aneurysms proved to be vascular malformations. Occlusion of the aneurysm and vascular malformation was successfully performed in 16 patients, resection of the vascular malformation was achieved in 1 patient, and the vertebral artery was clipped in 3 patients with fusiform aneurysms without complications related to the extreme lateral transcondylar approach. Unobstructed exposure of the aneurysm, parent artery, and neural structures without retraction of the sensitive lower brain stem are the major advantages of the extreme lateral transcondylar approach.     

Fenestrated basilar artery with ruptured cerebral aneurysms: case report

Two cases of aneurysms with basilar artery fenestration are presented. A 45 year-old lady had a saccular aneurysm associated with a fenestrated basilar artery. The fenestration was located in the proximal third of the basilar artery. The aneurysm arose from the proximal end of the fenestration, projecting antero-inferiorly. Via a left retromastoid craniectomy, the aneurysm was successfully obliterated through the space between the eighth cranial nerve and the lower cranial nerve complexes. Postoperative deficit in the lower cranial nerves was minimal and transient. The other patient, a 63 year-old lady, had multiple aneurysms arising from the anterior circulation associated with a basilar artery fenestration. These aneurysms were clipped uneventfully. Surgical approach to an aneurysm arising from the basilar artery fenestration is discussed with other related literature. Full study of posterior circulation with multiple projection is mandatory to detect basilar artery fenestration, and the possible presence of saccular aneurysm at the site of the anomaly.     

The use of electroencephalography and brain protection during operation for basilar aneurysms

Intraoperative monitoring with electroencephalography and the use of brain protection with steroids, phenytoin, mannitol, and pentobarbital or etomidate were evaluated in 15 patients undergoing operation for an aneurysm of the upper basilar artery. One patient harbored a basilar trunk aneurysm, 1 an aneurysm of the proximal posterior cerebral artery, 3 an aneurysm of the superior cerebellar artery, and 10 an aneurysm at the basilar tip. The size of the aneurysms varied between 5 and 30 mm. Subarachnoid hemorrhage was the symptom exhibited in 12, mass effect the symptom in 2, and 1 patient was asymptomatic but had an angiogram because of amaurosis. There were 9 patients with multiple aneurysms, 5 of whom had aneurysms of the bilateral anterior circulation. Four patients underwent operation early. In 2 patients, the basilar artery was the sole or main blood supply of the whole brain. All patients except the one with the basilar trunk aneurysm were operated on via a transsylvian approach. All patients received 500 to 800 mg of phenytoin and 10 to 20 mg of dexamethasone shortly before and during surgery, and mannitol (0.8 g/kg) 15 minutes before the induction of hypotension or temporary clipping. Three patients showed slowing of electrical activity over the right hemisphere as a result of retraction of the internal carotid artery; with repositioning of the retractor, this disappeared within 10 minutes. Electrocortical silence was induced in 8 patients; this was in anticipation of prolonged moderate hypotension in 2, short deep hypotension in 2, temporary clipping of major vessels--including the basilar artery--in 2, and a combination of deep hypotension combined with temporary clipping in 2.(ABSTRACT TRUNCATED AT 250 WORDS)     

A temporal approach to anterior communicating artery aneurysms. Technical note

As an alternative to approaching anterior communicating artery (ACoA) aneurysms through the frontal fossa, either parasagittally or laterally (pterional, gyrus rectus approach), this report describes an approach to ACoA aneurysms through the temporal fossa. The main advantages of this temporal technique are that it requires less brain retraction, gives better surgical orientation, gains control of both A1 segments before disturbing the aneurysm, and involves minimal resection of brain tissue. This temporal approach has recently been used by the author in 20 consecutive operations for ACoA aneurysms in preference to the gyrus rectus approach.     

Double aneurysms at distal basilar artery: report of nine cases

OBJECTIVE: Double aneurysms at the basilar bifurcation and the basilar artery-superior cerebellar artery (BA-SCA) junction have not been well investigated previously. We analyzed nine patients with double basilar aneurysms to evaluate their radiological characteristics and suitable treatment. METHODS: Between 1978 and 1999, the incidence of double aneurysms was 5.3% in our 169 consecutive surgical cases of distal BA aneurysms. Seven (77.8%) of the nine patients with double aneurysms had associated aneurysms in the anterior circulation. Open surgery was performed in eight patients and coil embolization in one. The patients' radiological findings, choice of treatment, and surgical results were analyzed retrospectively. RESULTS: The size of the basilar bifurcation aneurysms ranged from 2 to 8 mm (mean, 4.4+/-2.0 mm), and the size of the BA-SCA aneurysms ranged from 2 to 12 mm (mean, 5.6+/-3.6 mm). Diagnosis of double basilar aneurysms was difficult when the basilar trunk had twisted or when size differences between the two aneurysms were apparent. The angle between the posterior cerebral artery and SCA appeared to be wider on the same side as the BA-SCA aneurysms (101+/-42 degrees) than on the opposite side (26+/-24 degrees). The P1 segment of the posterior cerebral artery originated in an upright direction from the basilar bifurcation between the two basilar aneurysms in seven patients. The pterional approach was used in eight patients; 14 basilar aneurysms were successfully clipped and 2 were wrapped. Nonstraight clips with short blades were used frequently. Coil embolization of double aneurysms was required twice in one patient because the initial angiogram was misinterpreted as a single aneurysm and its bleb. CONCLUSION: Measurement of the posterior cerebral artery-SCA angle is a simple method to estimate the presence of BA-SCA aneurysms and to differentiate double aneurysms from a bilocular aneurysm at the basilar bifurcation. The pterional approach is suitable for clipping double basilar aneurysms because anterior circulation aneurysms often coexist, and the upstanding P1 segment is an obstacle in the subtemporal approach to the basilar bifurcation aneurysm. Nonstraight clips with short blades are convenient to avoid conflicting clips in the narrow surgical space.     

Electrophysiological monitoring during basilar aneurysm operation

Intraoperative brain stem auditory evoked potential (BAEP) and somatosensory evoked potential (SEP) monitoring was evaluated in 16 patients each undergoing intracranial operation for basilar artery aneurysm. The 16 patients had 18 posterior circulation aneurysms, including 2 patients with 2 aneurysms. Fourteen aneurysms arose from the rostral basilar artery, 2 arose from the midbasilar artery, 1 arose from the vertebrobasilar junction, and 1 arose from the proximal segment of the posterior cerebral artery. Five aneurysms were classified as giant (i.e., greater than 25 mm), and 5 aneurysms were large (i.e., 15 to 25 mm). Ten patients had BAEP and SEP monitoring, 4 had BAEP monitoring only, and 2 had SEP monitoring only. Two patients showed significant abnormalities during operation, including 1 patient with transient changes in the BAEP when the lower pons and the 8th cranial nerve were retracted. Another patient had progressive increases in latency and decreases in amplitude and subsequent loss of the SEP cortical components during a period of intermittent temporary rostral basilar artery occlusion. Wave P13 was also lost during that period. The cortical components as well as Wave P13 returned after circulation was restored. The BAEPs were unchanged in the same patient during the period of temporary basilar artery occlusion. Fourteen patients had no significant abnormalities. There were no consistent changes during the various stages of operation. BAEP and SEP monitoring failed to identify ischemic events in 4 patients with neurological findings of brain stem ischemia immediately after operation (i.e., 25% false-negative studies).(ABSTRACT TRUNCATED AT 250 WORDS)     

A transcavernous-transsellar approach to the basilar tip aneurysms

A series of 11 patients with a basilar tip aneurysm were treated operatively. The aneurysm had ruptured in all cases and caused at least one haemorrhage prior to surgery. Four patients harboured large aneurysms, while in the rest of them the aneurysms were small in size. In all the 11 patients a modified pterional transcavernous-transsellar approach was used which considerably facilitated clipping and secured complete exclusion of all aneurysms, including the large ones. Eight patients made a complete recovery and resumed their original occupation. One is hemiparetic but capable of self care, one is hemiplegic, and one died after surgery. The purpose of this report is to present our modified surgical approach to basilar tip aneurysms, which provides good exposure of the entire region of the bifurcation of the basilar artery and adjacent blood vessels as far as the anterior inferior cerebellar arteries, and requires but minimal retraction of the brain.     

Low Anterior Interhemispheric Approach – A Narrow Corridor to Aneurysms of the Anterior Communicating Artery

Summary. Summary. Background: Many approaches for clipping anterior communicating artery (ACoA) aneurysms are reported in the literature. We describe here a new approach called “low anterior interhemispheric approach” for clipping of ACoA aneurysms. Materials and Methods: A low anterior interhemispheric approach utilizing a unilateral frontal craniotomy flap with minimal unilateral frontal lobe retraction was used in treating four patients harboring an unruptured ACoA aneurysm. The approach axis is directed to the ACoA area itself with minimal exposure to the anterior cerebral vessels. Findings: In all patients, complete neck clipping was possible with minimal brain retraction, without vascular damage and preserved olfaction. Interpretation: This approach is preferred on anatomical grounds for cases of unruptured small and medium sized ACoA aneurysms projecting anteriorly or posteriorly because the anterior communicating artery complex area can be fully visualized with minimal manipulation of the frontal lobes and anterior cerebral arteries.     

Giant aneurysm arising from a single arteriovenous fistula in a child. Case report

A case is presented of a child with an arteriovenous fistula and a giant aneurysm located beside the brain stem under the right temporal lobe. It was successfully treated by clipping its feeding artery, a branch of the right posterior cerebral artery. The similarities to, and the differences from, aneurysms of the vein of Galen are discussed.     

Some considerations on surgical approaches to the anterior communicating artery aneurysms--radiological study of 122 cases

We studied the operative approaches to anterior communicating artery aneurysms by means of reviewing preoperative angiogram and operation records. During the past 5 years, 117 patients with anterior communicating artery aneurysms were operated on in our hospital. Among these, we examined 112 cases of which preoperative angiogram and operation records were satisfactory for this study. We checked the next points on the preoperative angiograms. Neck of aneurysm-planum sphenoidal distance. Direction of the anterior communicating artery. It means which A2 is anterior to the other A2 in the lateral view of angiogram. Size of aneurysm. We checked the next points on the operation records. Operative approach and the side of craniotomy. When the pterional approach was taken, the rectal gyrus was aspirated or not. This analysis derived these two conclusions as below. 1. In the literature, as the operative approach to anterior communicating artery aneurysm, the pterional approach has a lot of advantages. For example, the pterional approach was accomplished without extensive frontal lobe retraction, without mobilization of the temporal lobe, without sacrificing the olfactory tract, and so on. Moreover, in early stage after onset of SAH, it is possible to remove the subarachnoid blood extensively without obvious brain damage by the pterional approach. In this study, we paid attention to the correlation between the neck-planum sphenoidal distance and the fact of aspiration of the rectal gyrus in the pterional approach. The result is that the higher aneurysmal neck was, the more frequently the rectal gyrus was aspirated. So, if the neck-planum sphenoidal distance is under 12 mm, which includes the majority of the cases (94% of cases), we think the pterional approach is the best approach for anterior communicating artery aneurysm.(ABSTRACT TRUNCATED AT 250 WORDS)     

Transtentorial approach to the posterior temporomedial structures

The supracerebellar transtentorial (SCTT) approach, a modification of the infratentorial supracerebellar approach, facilitates simple and minimally invasive access to posterior temporomedial structures without requiring retraction of the temporal or occipital lobe. The SCTT approach was used in 16 patients over a 3-year period. Eleven patients harbored tumors confined to, or located mainly within, the posterior hippocampal formation, three patients harbored aneurysms (one ruptured posterior cerebral artery [PCA] aneurysm at the P2-P3 junction, one ruptured giant PCA [P2] aneurysm, and one giant basilar artery-superior cerebellar artery aneurysm), one patient had juvenile-type moyamoya disease, and one patient suffered from medically intractable epilepsy. In these patients, the SC     

Lateral suboccipital approach for vertebral and vertebrobasilar artery lesions

A modification of the unilateral suboccipital approach is elaborated and illustrated. This modification is useful for aneurysms of the vertebral artery, the vertebrobasilar junction, and the proximal basilar trunk, and for arteriovenous malformations of the inferolateral cerebellum. It entails extreme lateral removal of the rim of the foramen magnum toward the condylar fossa and posterolateral removal of the arch of the atlas toward the exposed vertebral artery. This extra bone removal allows an approach to the front of the brain stem from inferolaterally, after gentle upward and medial retraction of the tonsil, with minimal or no retraction of the medulla.     

Operative neurosurgery: personal view and historical backgrounds (3). Anterior circulation--pterional approach

Under the title of anterior circulation aneurysms and the pterional approach, followings are presented and emphasized along with mentioning their historical development in our present performance status. Pterional approach: head positioning with Mayfield-Kees fixation apparatus using one pin around the processus matoideus and the other 2 pins on the contralateral side behind the hair line the head turned 30 degrees and reclined chin-up l5-20 grade. Skin incision beginning just in front of the tragus ending up at the midline hair line in a curvilinear fashion always including the superficial temporal artery STA in its frontal branch and the facial nerve (frontal branch) in the skin flap. A muscle fascial preparation is so fashioned such that a strip of myofascial cuff is left at the linea temporalis and the temporal musculature is reflected and retracted towards the postero-basal direction in order to expose the pterion, for which a small short myofascial incision is added parallel to the skin incision towards the tragus up to several cm above it to prevent postoperative trismus. Bone flap is sawed out usually using three burr holes, at the key hole just at the proximal part of the linea temporalis, frontomedially on the squama frontalis and on the sutura squamosa, so that the Sylvian fissure and the superior temporal gyrus are exposed enough for further procedure. The sphenoid ridge is drilled away until the most lateral corner of the superior orbital fissure comes into view. Thus one has drilled away enough to do surgery in question at the skull base even at the time of "angry brain" due to subarachnoid hemorrhage SAH. This procedure can be followed by selective extradural anterior clinoidectomy SEAC in case of necessity. The dura is opened in a curvilinear fashion so that the dura can be reflected over the drilled sphenoid wing and so that the Sylvian fissure and the superior temporal gyrus is exposed for the treatment of aneurysms of the internal carotid artery ICA, of the anterior communicating artery AcomA and the middle cerebral artery MCA. The dural incision is suitable also for doing other surgeries e.g. basilar bifurcation aneurysms and amygdalohippocampectomy AHE. Following points are emphasised in aneurysm surgery at the acute stage of SAH: (1) Artificial hypotension of the systolic pressure down to 100 mmHg. (2) Use of temporary clipping (or trapping) method not only for the management of premature rupture but for complete dissection of aneurysms and for optimal neck clipping. (3) Opening of the lamina terminalis to gain slackness of "angry brain" and to insert an external ventricular drainage at the end of surgery for the intracranial pressure ICP registration and its regulation. (4) Importance of subpial approximation ("subpiale Ann?herung) at the time of aneurysm dissection to take advantage of the strength of the pia mater over (the arachnoid) and the dome of aneurysm. (5) Use of oxycellulose Tabotamp insertion technique between the aneurysm neck and neighbouring perforators to avoid inclusion of the latter ("Mitklippen") at the time of neck clipping. (6) Double clipping method at the time of incomplete neck clipping due to athromatous plaque. Combination of fenestrated clip and standard clip or "puncture and collapse" method at the time of aneurysm incorporation of parent and/or branching arteries. (7) Use of microDoppler to confirm patency of the parent arteries and their branches. For doing surgery of aneurysms of main cerebral arteries following points are discussed: (1) AcomA aneurysms; (a) Aneurysms located lower than 1.5 cm above the level of the anterior clinoid process in the lateral view on digital subtraction angiography DSA can be managed with conventional pterional approach. (b) Usually from the right side (non dominant hemisphere) but in the following situations from the left side: hematoma on the left side, concomitant unruptured aneurysms on the left side, left A1 dominancy at the acute stage of SAH and its dissection is considered to be difficult from the right side. (c) Always rectal gyrus approach to the aneurysm with any direction. This also enables safety subpial approximation "subpiale Annaeherung" to aneurysms. (d) No use of coagulation as much as possible. (2) ICA aneurysms; (a) Performance of selective extradural anterior clinoidectomy SEAC for paraclinoid aneurysms not only for aneurysm dissection but for proximal control. (b) Neither sacrifice nor Mitklippen of the posterior communicating artery at the time of ICA-PcomA aneurysms, not only for the prevention of the PCA infarction in case of its embryonal type but also for the prevention of tuberothalamic infarction due to compromise of the anterior thalamoperforating arteries originating from the PcomA. (c) Dissecting aneurysms of the ICA: difficulties of diagnosis or differentiation from paraclinoid anurysms. Difficulties of optimal direct clipping and resort to trapping or proximal ligation plus bypass. Its predilection site is at the medial anterior wall of the C1 portion but may occur also in any other portion of the ICA. (3) Middle cerebral artery MCA aneurysms; (a) For dissection, superior temporal gyrus ablation is not necessary but opening of the Sylvian fissure by retrograde tracing of a cortical artery on the surface of the temporal lobe. This cortical artery can be used as recipient when a bypass surgery turns out to be necessary with the use of a donor artery from the frontal branch of the STA. (b) Importance of interpreting DSA or 3DCT angiography in regard to whether the aneurysm dome is outside (lateral) or inside (medial) of the MCA bifurcation. This helps in anticipating whether the aneurysm dome or MCA branches come into view first at the time of intraSylvian dissection. (c) In case of presence of aneurysms at the contralateral MCA, accessibility from the ipsilateral side depends on the distance form the midline (for example early bifurcation), the relationship to the sphenoid wing (not below the level of the sphenoid wing) and no strong Sylvian vein darining into the sphenoparietal sinus being in the way.