Subtemporal Approach Research Articles

Combined Approach for Lesions Involving the Cerebellopontine Angle and Skull Base: Experience with 30 Cases

This article presents a series of 30 patients who underwent a combination of the subtemporal and posterior fossa approaches for exposure of lesions in the clivus or medial petrous region. This combined supra- and infratentorial approach is divided into three variations with progressively greater petrous bone resection to increase exposure of the clivus and medial petrous region. The approach has been divided into petrous bone resection with preservation of hearing (retrolabyrinthine), greater petrous bone resection with sacrifice of hearing (translabyrinthine), and finally maximum petrous drilling with sacrifice of hearing along with transposition of the facial nerve (transcochlear). Ninety-three percent of the cases returned to their premorbid occupations.

Tegmental dehiscence and brain herniation into the middle ear cleft

The tegmen tympani may occasionally be breached by herniation of the temporal lobe with or without dural cover. The clinical presentation may be obvious with CSF otorrhoea but less so with apparent middle ear effusion, CSF rhinnorrhoea, conductive hearing loss, recurrent meningitis or intracranial sepsis. Diagnosis requires suspicion of the condition, which may be aided by radiological imaging. Surgical repair is to be recommended: various techniques are available but bone enveloped by fascia placed by subtemporal approach is preferred. The features of this problem are highlighted by four cases.

Lower basilar artery aneurysm に対する transpetrosal approach

The lower basilar artery aneurysm is one of the most difficult to approach surgically because of its anatomy. The microsurgical anatomy which is encountered while dissecting cadaver specimens with a transpetrosal approah is presented in this paper. The routes used for this approach are 1) subtemporal approach, 2) retrolabyrinthine approach and 3) supra- and infratentorial approach which combines a retrolabyrinthine approach with a retromastoid-posterior subtemporal approach. With this approach, direct visualization of the lower basilar artery and its vicinity are possible with minimum distance and with minimum brain retraction. However, the surgical field is limited and there exists a risk of disturbing the vestibulocochlear function. So, a thorough knowledge of the anatomy of the petrous portion of the temporal bone and skilful drilling of this bone are indispensable. The landmarks which are the most useful for these approaches are the greater petrosal nerve for a subtemporal approach, and anterior margin of the sigmoid sinus, the superior petrosal sinus and the vestibular aqueduct for a retrolabyrinthine approach.

解剖学的見地からみた高位脳底動脈分岐部動脈瘤に対する手術

Surgery of a high basilar bifurcation aneurysm is one of the most difficult operations because of the location. Aneurysms which are located 1.5cm higher than the posterior crinoid process are difficult to approach by the usual pterional or subtemporal approaches. Our original transzygomatic anteriorsubtemporal approach is useful for aneurysms located up to 2cm higher than the posterior crinoid process. The patient is placed in a semiprone position with the face turned 60°contralaterally. The skin incision is started from the external auditory meatus. The zygomatic arch is reflected with the temporal muscle. The bone of the middle fossa is removed. The temporal lobe is retracted upwards after dural incision. The tentorial edge, PCA, fourth nerve and third nerve are recognized first. Then we approach the basilar artery and a highly situated aneurysm. In this report, authors explain this useful approach from an anatomical standpoint.

解剖学的見地からみた高位脳底動脈分岐部動脈瘤に対する手術

Surgery of a high basilar bifurcation aneurysm is one of the most difficult operations because of the location. Aneurysms which are located 1.5cm higher than the posterior clinoid process are difficult to approach by the usual pterional or subtemporal approaches. Our original transzygomatic anteriorsubtemporal approach is useful for aneurysms located up to 2 cm higher than the posterior clinoid process. The patient is placed in a semiprone position with the face turned 60°contralaterally. The skin incision is strated from the external auditory meatus. The zygomatic arch is reflected with the temporal muscle. The bone of the middle fossa is removed. The temporal lobe is retracted upwards after dural incision. The tentorial edge, PCA, fourth nerve and third nerve are recognized first. Then we approach the basilar artery and a highly situated aneurysm. In this report, authors explain this useful approach from an anatomical standpoint.

Neurinoma in the Cavernous Sinus: Report of Two Cases

Abstract Two cases of trigeminal neurinoma located solely in the cavernous sinus are reported. Preoperatively, magnetic resonance imaging provided the accurate localization of the lesions, allowing precise planning of the surgical approach, that is, a subtemporal lateral approach and a pterional superior approach, respectively. The neurinomas inside the cavernous sinus were removed successfully, and the patients developed no new neurological deficits except for anesthesia in the 1st division of the trigeminal nerve. The characteristic magnetic resonance imaging findings of trigeminal neurinoma in the cavernous sinus are presented, and the different surgical approaches are discussed.

Neurinoma in the cavernous sinus

Two cases of trigeminal neurinoma located solely in the cavernous sinus are reported. Preoperatively, magnetic resonance imaging provided the accurate localization of the lesions, allowing precise planning of the surgical approach, that is, a subtemporal lateral approach and a pterional superior approach, respectively. The neurinomas inside the cavernous sinus were removed successfully, and the patients developed no new neurological deficits except for anesthesia in the 1st division of the trigeminal nerve. The characteristic magnetic resonance imaging findings of trigeminal neurinoma in the cavernous sinus are presented, and the different surgical approaches are discussed.

Fronto-temporal approach with orbito-zygomatic removal surgical anatomy

Removal of the orbital rim and the zygomatic arch can be associated with fronto-temporal craniotomy to gain additional space, so as to decrease cerebral retraction. In order to quantify the gain provided by this enlarged approach, the authors underwent anatomical studies comparing the field view angle of various intracranial targets with and without orbito-zygomatic removal, in 11 fresh human cadavers with the brain in situ. The field view angle was increased, thanks to orbito-zygomatic removal, on average, by 75% in the sub-frontal approach, 46% in the pterional approach, and 86% in the sub-temporal approach. Such approaches can be very useful for access to difficult lesions located in the vicinity of the skull base. In the last 3 years 21 patients were operated upon using this technique, with excellent results.

The subtemporal and preauricular infratemporal approach to intradural structures ventral to the brain stem

The subtemporal and preauricular infratemporal operative technique is an approach to the skull base through the anterior portion of the petrous temporal bone and is used for the removal of predominantly extradural tumors in this region. The present study, based on dissection of human cadavers, describes the use of this approach for the management of intradural lesions in the region of the clivus. Its main advantages include avoidance of brain retraction, the use of an extrapharyngeal route, and exposure of the ventral aspect of the pons and medulla and related structures caudal to the trigeminal root. This approach can easily be combined with an intradural subtemporal approach to provide additional exposure of the superior clivus rostral to the trigeminal root. Combining the two approaches provides direct access to the ventral surface of the entire brain stem from the dorsum sellae to the hypoglossal foramina. Five patients with lesions in the clivus and petrous apex have been operated on via this approach. Details of the anatomical aspects of the approach and its applications are presented.

Combined Pterional‐Anterolateral Approaches to Cranial Base Tumors

Advanced tumors of the paranasal sinuses, parotid gland, orbit, parapharynx, and cranial cavity may invade the infratemporal fossa by direct extension or through natural anatomic pathways. The inability to control disease involving this region is reflected by the unacceptably high recurrence rates for both intracranial and extracranial neoplasms. Between 1983 and 1986, a pterional (or subtemporal) approach was combined with such conventional anterolateral procedures as a mandibulopharyngectomy, maxillectomy, orbitectomy, and parotidectomy in 13 patients with advanced skull base lesions. The tumor origin was extracranial in ten cases and intracranial in three patients. Seven of the neoplasms were malignant and six were histologically benign. Complete tumor removal was achieved in all patients. Repair of the ablative defect was achieved with a temporalis myogenous flap in ten patients, and primary closure or distant myocutaneous flaps in the remaining three patients. Postoperative complications included three lateral nasocutaneous fistulae secondary to temporalis myogenous flap necrosis and isolated cases of stroke, cerebral edema, pneumocephalus, and cerebrospinal fluid rhinorrhea. Twelve patients are alive without evidence of disease at a mean interval of 25 months. The remaining patient died from lung metastases 11 months after surgery.

Microsurgery of Midbrain Lesions

Abstract Of 41 patients with midbrain lesions, 25 underwent definitive surgical exploration. In 16 patients surgical exploration was not warranted, since the patients had only slight neurological deficits and longstanding histories or consent was not given. The infratentorial supracerebellar approach proved to be the ideal method of exposure in 20 patients, in whom the lesion was located in the more dorsal aspect of the midbrain. In 6 of these patients the mass lesion extended from the cerebellum into the midbrain and, therefore, a transcerebellar route was also needed for exposure. In 5 patients the subtemporal approach was chosen. Three patients died as a result of the operation, but in the other 22 patients no increase in morbidity after surgery was apparent and the immediate postoperative course was normal. Five patients with malignant tumors died from recurrence despite radiotherapy. The remaining 17 patients have been doing well up to 14 years after surgery, but 3 had only limited follow-up. This experience with surgical exploration and total resection or evacuation of midbrain lesions in 25 patients should prove the safety of modern microsurgical techniques. Emphasis is placed on the benefit of microtopographic considerations in the choice of the most suitable approach to these deepseated lesions.

Microsurgery of midbrain lesions

Of 41 patients with midbrain lesions, 25 underwent definitive surgical exploration. In 16 patients surgical exploration was not warranted, since the patients had only slight neurological deficits and longstanding histories or consent was not given. The infratentorial supracerebellar approach proved to be the ideal method of exposure in 20 patients, in whom the lesion was located in the more dorsal aspect of the midbrain. In 6 of these patients the mass lesion extended from the cerebellum into the midbrain and, therefore, a transcerebellar route was also needed for exposure. In 5 patients the subtemporal approach was chosen. Three patients died as a result of the operation, but in the other 22 patients no increase in morbidity after surgery was apparent and the immediate postoperative course was normal. Five patients with malignant tumors died from recurrence despite radiotherapy. The remaining 17 patients have been doing well up to 14 years after surgery, but 3 had only limited follow-up. This experience with surgical exploration and total resection or evacuation of midbrain lesions in 25 patients should prove the safety of modern microsurgical techniques. Emphasis is placed on the benefit of microtopographic considerations in the choice of the most suitable approach to these deep-seated lesions.

Surgical Removal of Pontomesencephalic Cavernous Hemangiomas

Abstract Cavernous hemangiomas of the brain stem are usually discovered accidentally during evacuation of a hematoma, and successful surgical treatment of these lesions is seldom achieved. With the increasing use of magnetic resonance imaging, the presence of a cavernous hemangioma can be detected before surgery, allowing an elective surgical approach. We successfully removed pontomesencephalic cavernous hemangiomas from 2 patients and pontomedullary hemangiomas from 2 others. Elective surgery was performed with perioperative bimodal monitoring of somatosensory and auditory evoked potentials. Performing surgery soon after the hemorrhage minimizes the risk of additional postoperative neurological deficit, since surgical excision is facilitated when the hematoma is not completely organized. Pontine hemangiomas are approached via the 4th ventricle. Mesencephalic hemangiomas are removed by a midline supracerebellar approach when they are lateralized by using a subtemporal approach. The lesion can be removed through a small incision in the brain stem at the site of the lesion. The favorable results, which include marked improvement of preoperative neurological deficits and documentation of complete removal of the lesion by magnetic resonance imaging, support a more aggressive approach to the treatment of symptomatic cavernous hemangiomas of the brain stem. Further investigation of the natural history of these lesions is mandatory.

Surgical removal of pontomesencephalic cavernous hemangiomas

Cavernous hemangiomas of the brain stem are usually discovered accidentally during evacuation of a hematoma, and successful surgical treatment of these lesions is seldom achieved. With the increasing use of magnetic resonance imaging, the presence of a cavernous hemangioma can be detected before surgery, allowing an elective surgical approach. We successfully removed pontomesencephalic cavernous hemangiomas from 2 patients and pontomedullary hemangiomas from 2 others. Elective surgery was performed with perioperative bimodal monitoring of somatosensory and auditory evoked potentials. Performing surgery soon after the hemorrhage minimizes the risk of additional postoperative neurological deficit, since surgical excision is facilitated when the hematoma is not completely organized. Pontine hemangiomas are approached via the 4th ventricle. Mesencephalic hemangiomas are removed by a midline supracerebellar approach when they are lateralized by using a subtemporal approach. The lesion can be removed through a small incision in the brain stem at the site of the lesion. The favorable results, which include marked improvement of preoperative neurological deficits and documentation of complete removal of the lesion by magnetic resonance imaging, support a more aggressive approach to the treatment of symptomatic cavernous hemangiomas of the brain stem. Further investigation of the natural history of these lesions is mandatory.

視床AVMの手術

In this report, three operations for thalamic arteriovenous malformation (AVM) are discussed, mainly from the viewpoint of surgical approach and technique.Case 1 was a 20-year-old male with a history of three episodes of intracranial hemorrhage. Angiogram demonstrated a nidus 2cm in diameter at the anterior inferior site of the left thalamus. The malformation was fed by anterior and posterior choroidal arteries and the anterior thalamoperforating artery. First surgery was performed using a subtemporal approach. The left posterior communicating artery which mainly fed the nidus was trapped. Second surgery was performed via a bifrontal craniotomy. An anterior transcallosal approach was used to expose the AVM. Nidus was totally excised via the left lateral ventricle. Postoperatively, no new neurological deficit appeared.Case 2 was a 36-year-old female who experienced a sudden intraventricular hemorrhage. Angiogram demonstrated a nidus 2cm in diameter at the posterior superior site of the left thalamus. The malformation was fed by the anterior and posterior choroidal arteries. Surgery was performed via a left parietal craniotomy. A transparietal approach was used to expose the AVM and the nidus was totally excised. Although the patient exhibited Gerstmann syndrome and right homonymous hemianopsia, they were transient, and the patient was discharged with no deficit.Case 3 was a 51-year-old female with a history of three episodes of intracranial hemorrhage. Angiogram demonstrated a nidus 4cm in diameter at the right thalamus. The malformation was fed by the anterior and posterior choroidal arteries, the anterior thalamoperforating artery and the thalamogeniculate artery. Surgery was performed via a right fronto-temporo-parietal craniotomy. At first, the feeder was clipped using a subtemporal approach. And then the nidus was totally excised using a transparietal and transventricle approach. Postoperatively, impairment of consciousness appeared.It appeared to be important in surgery for AVM's in a critical area like the thalamus that management of the feeder be performed first, bleeding should be avoided as much as possible, and the normal brain tissue should not be damaged. Although the border between the nidus and the normal brain tissue should be ascertained, MRI was considered to be useful in determining these relationships. While it is reasonable to excise the thalamic AVM via the lateral ventricle, it is difficult to manage the feeder at first. Previous feeder clipping was useful in two cases. The trans parietal approach was used in two cases. Even at the dominant hemisphere, neurological deficit associated with this approach did not remain. Monitoring of SEP and using doppler sonography were also useful.

Surgical Approach to Arteriovenous Malformation of the Medial Temporal Lobe

We report three cases of arteriovenous malformation (AVM) of the medial temporal lobe and the surgical approaches used. The AVM was fed by the anterior choroidal artery (AChA) in two cases (Cases 1 and 2) and by the posterior cerebral artery in one (Case 3). The trans-Sylvian approach was first used for cerebrospinal fluid aspiration to retract the brain in all cases, and for confirming the feeding arteries to prevent premature bleeding from the AVM in Cases 1 and 2. In Case 1, a corticotomy was then made in the fusiform gyrus via the subtemporal approach to avoid the development of speech disturbance and visual field defects, while in Cases 2 and 3, a cortical incision was made in the middle temporal gyrus because visual field defects were preoperatively present. Cases 1 and 2 achieved good recoveries, but Case 3 suffered postoperative speech disturbance and died of rebleeding from a recurrent AVM fed by the AChA 22 months after the operation. This AVM was not demonstrated on the postoperative angiograms. We emphasize the usefulness of the combination of trans-Sylvian and subtemporal approaches for this lesion, because the feeding arteries are easily identified and retraction of the temporal lobe is alleviated. A corticotomy in the fusiform gyrus is also recommended to avoid the development of not only visual field defects but also aphasia.

<I>Fusiform Superior Cerebellar Artery Aneurysm Presenting with Contralateral Abducens Nerve Paresis</I>

A 25-year-old female suddenly developed headache and diplopia. On admission, neurological examination revealed neck stiffness and left abducens nerve paresis. A computed tomographic scan suggested subarachnoid hemorrhage. Left vertebral angiogram showed an aneurysm on the anterior pontine segment of the right superior cerebellar artery (SCA) and marked flexion and meandering of the basilar artery to the left. At surgery, an atherosclerotic, fusiform aneurysm was found through the right subtemporal transtentorial approach, and the right SCA was clipped just proximal to the aneurysm. Thirteen cases of SCA aneurysm have been described in the literature, but none was a fusiform aneurysm.

Mesencephalic haematoma, successful surgical evacuation: Case report

A case of mesencephalic haematoma is reported. Emergency surgical evacuation of haematoma was done. The patient improved and has done well for five years. Subtemporal and infratentorial supracerebellar approaches have been used earlier to remove mesencephalic haematoma. It is possible to remove caudal midbrain haematoma via a IVth ventricular approach causing minimal damage.

Anatomical basis of the extended subtemporal approach to the cerebellopontine angle: its value and limitations.

The cerebellopontine angle is an anatomic region situated deeply at the anterolateral aspect of the brainstem, access to which is complicated by the presence of neurovascular bundles. The functional importance of these cranial n. (trigeminal, facial, vestibulo = cochlear, glossopharyngeal, vagus and accessory) calls for the use of special surgical routes of access in certain cases. In particular, tumors situated between the vestibulocochlear-facial bundle behind and the trigeminal n. in front are difficult to reach by the suboccipital and subtemporal transmeatal routes. The endeavor to preserve hearing in particular situations, where the side opposite the tumor is no longer functional, justifies the use of a subtemporal transmeatal route extended by opening the tentorium cerebelli. This anatomic and experimental surgical study deals with the possibilities of this route of approach.

椎骨脳底動脈合流部動脈瘤に対するtranspetrosal-anterosigmoidal approachの1例

Clipping a vertebrobasilar union aneurysm is one of the most difficult surgical procedures, because it is deep and surrounded by many important structures, such as the brain stem, lower cranial nerves and cerebellum.We have experienced a successful clipping of the aneurysm at this portion through a transpetrosal-anterosigmoidal approach. We report it and discuss the approaches to aneurysm at this portion.This approach has many advantages: 1) A small scalp incision. 2) Drilling the posterior pyramis is easy, because the procedure is superficial. 3) Both side of parent artery of the aneurysm can be kept. 4) Little damage to the brain stem, cerebellum and cranial nerves by retractions. 5) Short cut to the aneurysm. 6) A subtemporal approach can be easily combined if it should be required.