Subtemporal Approach Research Articles

Microsurgical removal of the cavernous malformations in the brainstem

Objective To investigate the mierosurgical time windows, techniques and prognosis of removing cavernous malformations in brain stem. Method The clinical materials of 10 cases of cavernous malformations of brain stem removed by microsurgery and demonstrated by pathological examinations were studied retrospectively. All the cases were examined preoperatively by cr and MRI. One lesion located in midbrain,7 lesions in pons and 2 lesions in medulla. The lesion in midhrain was removed by subtemporal approach,lesions in medulla and part of the lesion in pons were removed by subocciptal middle approach, and the other part of the lesions in pons were removed by retrosigmoid approach. GOS system was used to evaluate the prognosis. Results All the lesions were removed radically under microscope and no death arose. Pathological examination demonstrated all the lesions were cavernous malformations. All the cases were followed up from 3 months to 48 months with the average time 18. 5 months. 10 patients were evaluated by GOS system at 3 months after operation. There were 5 cases of GOS grade V and 5 cases of grade IV. 10 patients were evaluated by GOS system at 1 year after operation. There were 8 eases of GOS grade Ⅴ and 2 eases of grade Ⅳ. There was no bleeding after operations. Conclusions Microsurgery is an effective way to cure cavernous malformations in hrainstem, and the long-term prognosis is satisfying. Key words: Hemangioma,cavernous,central nervous; Brain stem; Microsurgery

Opening cranial cisterns in anterior subtemporal keyhole approach to superior petroclival region:anatomic study and comparative analysis

Objective To quantitatively compare the exposure areas and angles in anterior subtemporal keyhole approach to superior petroclival region before and after cranial cisterns opening. Methods The study was carried out on 20 sides of cadaver heads. With application of a navigation system, the exposure area in superior clivus, the ventrolateral area in brain stem around BA, the linear exposure of the posterior petroclinoid fold and BA trunk, and the approach angles to BA tip were evaluated. Results The exposure area in superior clivus （ 136. 7 ± 19. 8 ） mm^2, the ventrolateral area in brain stem （ 222. 8 ± 25.8 ） mm^2, the linear exposure of the posterior petroclinoid fold （ 11.5 ±0. 6 ） mm, and BA trunk （10. 3± 2.0 ）mm, and the approach angles in the vertical axis to BA tip（ 13.7 ± 1.7 ）°were significantly greater after opening cranial nerve cisterns. But the approach angles in the horizontal axis to BA tip were indifferent. Conclusions The exposure areas and angles of anterior subtemporal keyhole approach to superior petroclival region can be increased after opening cranial nerve cisterns. Key words: Subtemporal; Keyhole approach; Cranial nerve cisterns ; Superior petroclival region

The Subtemporal Approach: A Road Less Traveled

Introduction: The subtemporal approach was popularized by Dr. Charles Drake for the microneurosurgical clipping of aneurysms of the distal basilar artery. The competing approach for such problems was and still is the transsylvian approach to the interpeduncular region. Because an increasing proportion of cerebral aneurysms, particularly those of the basilar artery, are treated by endovascular methods, it is probable that the subtemporal approach is being used less and less in contemporary neurosurgical practice. However, the elegance of this approach lends itself to the neurosurgical treatment of not only vascular lesions, but also for the definitive microsurgical management of tumorous lesions that occur in the deep, central portions of the cranial cavity.

Localized Neurosarcoidosis Resembling a Trigeminal Schwannoma: Case Report

A 24-year-old woman was referred to us with a trigeminal neuralgia refractory to medical therapy. Brain MRI disclosed a homogenously contrast-enhanced lesion located in Meckel's cave with a minor extension in the posterior fossa and impingement on the foramen ovale. The patient was operated on via a subtemporal interdural approach, and the mass was removed subtotally. Preoperative imaging and intraoperative macroscopic findings suggested a trigeminal schwannoma. The histological analysis showed no tumor, but inflammatory tissue compatible with sarcoidosis was seen. The neuralgia persisted and the patient underwent diagnostic workup for localized neurosarcoidosis. The patient underwent specific therapy with resolution of the clinical symptoms at 2 months from intervention. We will discuss this rare condition, which is difficult to diagnose.

A Giant Facial Nerve Schwannoma Extending from the Middle Cranial Fossa to the Mastoid Region: Case Report

Facial nerve schwannomas are uncommon benign tumours and seldom extend into the middle cranial fossa. This is a case report of a giant facial nerve schwannoma extending from the middle cranial fossa to the mastoid region, which was successfully removed using combined interdisciplinary subtemporal and transmastoid approaches. Complete resection of the tumour was the optimal therapy for this patient because the facial nerve had been severely destroyed by the tumour. The clinical presentation, histological features, radiological findings and management of this case, as well as the relevant literature, are presented.

Trigeminal nerve haemangioma eroding the petrous carotid canal

To report the first case of mandibular branch haemangioma of the trigeminal nerve causing erosion of the petrous carotid canal. The radiological and histological findings in this case are reviewed. A 60-year-old woman presented with severe, right-sided facial pain and paraesthesia. There were no associated symptoms of facial weakness or diplopia. A magnetic resonance imaging scan with gadolinium enhancement was performed. This showed a lesion slightly compressing the right Meckel's cave and eroding the right petrous carotid canal, occupying the foramen ovale and extending to the pterygoid muscle. The lesion was removed via a subtemporal approach. Haemangiomas are usually found on the skin and in other soft tissues. However, this rare tumour should also be considered in the differential diagnosis of lesions occupying Meckel's cave and the foramen ovale.

Opening cranial cisterns by the anterior subtemporal keyhole approach to the superior petroclival region: anatomical study and comparative analysis

Background Without drilling the bony structures, simple incision of the tentorium dorsal to the porus of trochlear nerve by the anterior subtemporal keyhole approach provides narrow exposure in the superior petroclival region. This study was designed to measure and compare the areas of exposure, linear distances, and angles of approach in the superior petroclival region before and after opening cranial cisterns. Methods The study was carried out on 20 sides of cadaver heads. With the use of a navigation system, the area of exposure in the dorsum sella and clivus, the ventrolateral area of exposure in brainstem around the BA, the linear exposure of the posterior petroclinoid fold and BA trunk, and the angles of approach to BA tip were evaluated. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus between trochlear porus, the linear exposure of the trigeminal nerve, and the angle to the most inferior medial point in clivus were also measured. Results The area of exposure in the dorsum sella and clivus (157.6 ± 27.2mm 2), the ventrolateral area of exposure in brainstem around BA (249.5 ± 29.7mm 2), the linear exposure of the posterior petroclinoid fold (11.5 ± 0.6 mm) and BA trunk (10.3 ± 2.0 mm), and the angle of approach in the vertical axis to the BA tip (13.7° ± 1.7°) were significantly greater after opening cisterns. The angles of approach in the horizontal axis to the BA tip (24.5° ± 1.1° vs 24.7° ± 0.8°) were not statistically different. The length of oculomotor cistern and trochlear cistern, the distance of oculomotor porus and trochlear porus, the linear exposure of the trigeminal nerve, and the angle of approach to the most inferior medial point in clivus were 6.7 ± 1.3 mm, 10.7 ± 2.4 mm, 9.6 ± 2.3 mm, 15.8 ± 1.4 mm, and 13.0° ± 1.5°, respectively. Conclusion The areas of exposure, linear distances, and the angles of approach in the superior petroclival region can be increased after opening cranial cisterns by the anterior subtemporal keyhole approach.

Tuberculoma of the cavernous sinus mimicking a meningioma: Case report and review of the literature

Cavernous sinus involvement of tuberculosis is rare; only seven cases have been reported in the literature to date. Many factors make the diagnosis difficult in this location, necessitating a surgical procedure. We report the case of a 45-year-old man who presented with a left cavernous sinus syndrome clinically. The lesion mimicked a meningioma of the cavernous sinus in radiological examinations. It was entirely excised through a subtemporal approach. Histopathological examination revealed caseating granuloma and the diagnosis of tuberculoma was established. Postoperative antituberculous drugs completed the treatment and led to complete resolution of neurological symptoms. In our paper, we emphasize the rarity of the lesion in this location, we review all the cases previously published underlining the main epidemiological, clinical, radiological, therapeutic and prognostic features.

Infratemporal Metastasis From Occult Follicular Thyroid Carcinoma

An extremely rare case that has not been reported before is described in which metastasis of a follicular carcinoma of the thyroid is resected from the infratemporal fossa. The patient had not been diagnosed of this thyroid pathology. She underwent a left subtemporal preauricular approach, but after this, she had another subtemporal preauricular approach with total thyroidectomy, a facial translocation by degloving, and an endoscopic surgery, because of a local recurrence, and a sella turcica and sphenoidal sinus metastasis. Six years after this, the patient was free of recurrence. Surgical excision of metastatic thyroid lesions may be the only effective treatment but always followed by suppression therapy and whole-body iodine I 131 internal radiation. Stereotactic radiosurgery is a feasible option to treat skull base metastasis of this kind of tumor.

Limited access inferior temporal gyrus approach to mesial basal temporal lobe tumors

In this retrospective review, the authors examine the clinical characteristics, diagnosis, and outcome of surgery in 25 consecutive patients with mesial basal temporal lobe (MBTL) tumors. A limited access approach to the inferior temporal gyrus (ITG) was used. Patients with MBTL tumors were identified from the epilepsy and tumor surgery database at the authors' institution. Intraaxial tumors localized to the mesial basal structures, and without involvement of the cortical surface of the temporal lobe, temporal stem, and basal ganglia were included. Preoperative and postoperative MR images were obtained in all patients. The mean follow-up period was 24 months (range 9-36 months). Preoperative symptoms, neurological deficits, outcomes, surgical complications, and a technical description of the approach are discussed. Intraaxial MBTL tumors in 25 patients (mean age 44 years, range 8-76 years) were resected using a limited access approach via the ITG. The largest groups of tumors were high-grade gliomas and dysembryoblastic neuroepithelial tumors (8 in each group), followed by oligodendrogliomas, cerebral metastases, and gangliogliomas. Seizures, headaches, and disorientation were the most common preoperative symptoms. Postoperative MR images demonstrated gross-total resection in all cases. There were 2 surgical complications (a superficial wound infection and a transient frontalis branch palsy). There were no permanent neurological complications or significant new hemianoptic defects. A limited access ITG approach performed with intraoperative image guidance offers an alternative corridor for resection of MBTL tumors (Schramm Type A). This approach may be technically less demanding than the transsylvian or subtemporal approach. Gross-total resection is feasible utilizing this approach and compares favorably with other, more classical approaches.

Pneumococcal meningitis secondary to intra-sphenoidal encephalocoele

Basal encephalocoeles are rare congenital abnormalities of the skull base. The authors describe a rare case of spontaneous CSF leak and meningitis secondary to an intra-sphenoidal encephalocoele. Initial endoscopic transsphenoidal repair was unsuccessful, necessitating a combined subtemporal and transsphenoidal approach to close the defect.

Fronto-temporo-orbitozygomatic craniotomy and "half-and-half" approach for basilar apex aneurysms

Basilar apex aneurysms (BAA) are located in interpeduncular cistern surrounded by eloquent neurovascular structures. Surgical access is difficult due to narrow surgical corridors and requires traversing through a depth of 6-8 cm of subarachnoid space. Surgical management of BAAs clipped using frontotemporal craniotomy, orbitozygomatic osteotomy with combined subtemporal and transylvian (half and half) approach is discussed. Tertiary care referral institute; prospective study. Five patients with BAA rupture causing subarachnoid hemorrhage presented in modified Hunt and Hess (Hand H) grades II (n=1), III (n=1) and IV (n=3), respectively. In 4 patients, the aneurysms were 0.8-1.2 cm in diameter, situated 7 mm-1 cm above dorsum sellae. Two of them had posteriorly projecting aneurysms. One patient had a giant, high BAA with a left parietooccipital arteriovenous malformation. Vasospasm of posterior cerebral/proximal basilar artery was seen in 2 patients. In one patient, internal carotid artery was mobilized by intradural anterior clinoid drilling with carotid collar division. Triple-H therapy was administered following surgery. There was no intraoperative rupture or temporary clipping. Follow up angiography showed complete aneurysmal obliteration with preservation of posterior cerebral and superior cerebellar arteries. Follow up (mean: 8.7+/-3.5 months) H and H grades were II (n=2) and III (n=3), respectively. The morbidity include caudate and thalamic region infarct, transient III rd nerve palsy and cerebrospinal fluid otorrhoea (n=1, respectively). This simple approach provides a wide surgical corridor from 5 mm below to greater than 1 cm above dorsum sellae with adequate proximal control of basilar artery. It is an option to endovascular embolization especially with large and giant, or wide-necked BAA, vertebrobasilar tortuosity, coil compaction or postcoiling re-rupture and an associated large haematoma.

Surgical Strategy for Tumors Located in or Extending From the Intracranial Space to the Infratemporal Fossa -Advantages of the Transcranial Approach (Zygomatic Infratemporal Fossa Approach) and the Indications for a Combined Transcranial and Transcervical Approach-

The surgical strategy for tumors located in or extending from the intracranial space to the infratemporal fossa was analyzed in 12 cases with various pathologies. A case of mandibular nerve schwannoma, which extended 1 cm below the external orifice of the foramen ovale, was completely removed via the epidural subtemporal approach without zygomatic osteotomy with partial removal of the middle cranial base. The inferior margin of infratemporal tumor could be accessed via the transcranial route with zygomatic or orbitozygomatic osteotomy without complications including facial nerve injury in nine cases, and the lowest level of the infratemporal tumors was approximately 4.5 cm below the outer surface of the middle cranial base. In five of these 9 cases (2 schwannomas, 1 myxoma, 1 chondrosarcoma, and 1 malignant peripheral nerve sheath tumor), the tumors were localized in the infratemporal fossa, and in the other 4 cases (2 meningiomas, 1 glioblastoma, and 1 ameloblastoma), the tumors extended to both the intracranial space and the infratemporal fossa. In two cases (recurrent jugular schwannoma and mandibular osteosarcoma), a combined transcranial and transcervical approach (mandibular swing approach) was essential, because the resection line of the lower margin was too far from the middle cranial base. These results indicate that the transcranial approach, with or without zygomatic or orbitozygomatic osteotomy (zygomatic infratemporal fossa approach), is safe and effective for removal of some infratemporal tumors, and that a combined transcranial and transcervical approach is useful for removing infratemporal tumors with extensive downward extension.

Tentorial Incision in a Lateral-medial Direction with Minimal Retraction of the Temporal Lobe in the Subtemporal Transtentorial Approach to the Middle Tentorial Incisural Space

The subtemporal transtentorial approach provides excellent exposure of the middle incisural space. A modification of the subtemporal transtentorial approach with use of a partial mastoidectomy is presented to avoid damage to the temporal lobe as a result of retraction as well as damage to venous structures. Four patients, one with a superior cerebellar artery aneurysm, one with a metastatic tumor in the midbrain, one with a tentorial meningioma, and one with a tentorial schwannoma were treated with the present approach. After subtemporal craniotomy, all of the cortical bone overlying the mastoid was removed. The mastoid air cells were drilled down, and the upper part of Trautman's triangle was exposed above the level of the lateral semicircular canal. The presigmoid dura and the temporal dura were opened and connected by incising the superior petrosal sinus. The cerebellar tentorium was incised in a lateral-medial direction along the angle of the tentorium. In each case, the tentorium was incised with minimal retraction of the temporal lobe without any damage to the temporal lobe, or venous structures. The present approach yielded excellent visualization of the lesion and adjacent neurovascular structures. In 3 of 4 cases, the lesions were successfully treated. In the patient with a tentorial schwannoma extending from the middle to posterior incisural space, the extreme lateral supracerebellar-infratentorial approach was combined with the present approach. Although additional partial mastoidectomy is time-consuming, it reduces the risk of damage to the temporal lobe as a result of retraction as well as damage to venous structures.

Cavernous angioma of the geniculate ganglion

Intracranial extraaxial cavernous angiomas are rare vascular malformations. Their occurrence at the geniculate ganglion of the facial nerve within the temporal bone is exceptional. The authors describe a 35-year-old man who developed a slowly progressing facial palsy. Initial cranial MR imaging showed no pathological findings, but 2 years later another MR examination detected a small tumor located at the geniculate ganglion of the facial nerve. The tumor was removed via a subtemporal approach. Histological examination revealed a cavernous angioma. Even small cavernomas located at the geniculate ganglion of the facial nerve may result in facial palsy. Isolated facial palsy in a young person should be monitored closely using imaging studies even if the initial imaging study is negative. Early decompression of the facial nerve may help to preserve its function.

CELLULAR SCHWANNOMA OF THE GREATER SUPERFICIAL PETROSAL NERVE PRESENTING WITH ABDUCENS NERVE PALSY AND XEROPHTHALMIA

Cellular schwannomas (CS) are rare in the cranial space. This report is the first of a patient with a greater superficial petrosal nerve CS presenting with abducens nerve palsy and xerophthalmia. A 16-year-old female patient presented with a 1-month history of diplopia. Neurological examination was normal except for the presence of right abducens nerve palsy. Schirmer's test revealed decreased tear secretion in the right eye. Computed tomography and magnetic resonance imaging showed a mass in the right petrous apex. It was thought that the schwannoma in our patient originated from the greater superficial petrosal nerve, based on the location of the tumor in addition to the absence of partial Horner's syndrome and a persistent decrease in tear secretion. The tumor was exposed with the use of a right subtemporal extradural approach and removed entirely. Pathological evaluation of the tumor revealed a CS. The abducens nerve palsy improved completely in the follow-up period, but the decreased tear secretion did not resolve. CS is one of the subtypes of ordinary schwannomas and exhibits malignant features on microscopic examination, although it has a good clinical prognosis. No adjuvant treatment was applied because of the tumor's benign character. The greater superficial petrosal nerve schwannoma should be considered in the differential diagnosis of the abducens nerve palsy and petrous apex mass.

Improved cerebral function in mesial temporal lobe epilepsy after subtemporal amygdalohippocampectomy

The functional changes that occur throughout the human brain after the selective removal of an epileptogenic lesion remain unclear. Subtemporal selective amygdalohippocampectomy (SAH) has been advocated as a minimally invasive surgical procedure for patients with medically intractable mesial temporal lobe epilepsy (MTLE). We evaluated the effects of subtemporal SAH on cerebral glucose metabolism and memory function in 15 patients with medically intractable MTLE with hippocampal sclerosis using [(18)F]-fluorodeoxyglucose PET (FDG-PET) and the Wechsler Memory Scale-Revised. The patients were evaluated before and 1-5 years (mean 2.6 years) after surgery. In patients with MTLE of the language-dominant hemisphere, the basal temporal language area was preserved by this surgical approach. Voxel-wise comparison of FDG-PET images was conducted using SPM5 to identify the brain regions showing postoperative changes in glucose metabolism (height threshold, P = 0.01 corrected for multiple comparisons; extent threshold, 100 voxels). During spatial normalization of the postoperative FDG-PET images, we used cost-function masking to minimize any inappropriate image distortion as a result of the abnormal signal within the surgically resected region. Postoperative glucose metabolism increased in extratemporal areas ipsilateral to the affected side, such as the dorsolateral prefrontal cortex, and the dorsomedial and ventromedial frontal cortices. Glucose metabolism also increased in the bilateral inferior parietal lobules and in the remaining temporal lobe regions remote from the resected mesial temporal region, such as the superior temporal gyrus and the temporal pole. By contrast, postoperative glucose metabolism decreased only in the mesial temporal area adjacent to the resected region. Postoperative verbal memory, delayed recall and attention/concentration scores were significantly better than preoperative scores regardless of the resected side. This study suggests that the selective removal of the epileptogenic region in MTLE using a subtemporal approach improved cerebral glucose metabolism in the areas receiving projections from the affected mesial temporal lobe. Cognitive improvement might result from a combination of good seizure control and minimizing the regions of the brain with postoperative functional impairment.

Proximal STA to proximal PCA bypass using a radial artery graft by posterior oblique transzygomatic subtemporal approach

The aim of the present study was to investigate the use of a radial artery graft (RAG) for bypass of the proximal superficial temporal artery (STA) to proximal posterior cerebral artery (PCA) by posterior oblique transzygomatic subtemporal approach as an alternative to the external carotid artery (ECA) to PCA anastomosis. We conducted an anatomical and technical study at a university hospital. Five adult cadaveric specimens were dissected. A preauricular vertical skin incision was used. The trunk of STA was identified. A 30 degrees oblique posterior zygomatic arch osteotomy and microcraniotomy was performed. The dura of the middle cranial fossa was then opened. The temporal lobe was retracted, the interpeduncular and ambient cisterns were opened, and the P2 segment of the PCA was exposed. The proximal side of the RAG was anastomosed with the proximal STA and the distal side was anastomosed with the P2 segment. The mean caliber of the proximal STA was 2.25 +/- 0.35 mm. The mean diameter of the P(2) was 2.2 +/- 0.2 mm. The average length of the RAG was 56 +/- 3.2 mm. The mean caliber of the proximal and the distal sides of the graft was 2.5 +/- 0.25 mm and 2.3 +/- 0.15 mm, respectively. Because the proximal STA to proximal PCA bypass uses a short RAG and their calibers are over 2 mm, this bypass technique can provide a sufficient blood flow and may be a reasonable alternative over ECA to PCA bypass using long grafts.

Anterior Transpetrosal Approach to Petroclival Meningiomas

The best approach to petroclival meningiomas provides a wider exposure with decreased distance to the target and also minimizes brain retraction. For tumors located at the upper third of the clivus, a subtemporal approach with selective resection of the anterior part of the petrous pyramid offers a surgical field of the parasellar area, upper clivus, and the cerebellopontine angle. The extradural bone work serves to improve the exposure of the area in front of the upper brainstem from the intradural subtemporal route. Of the 87 cases of petroclival (premeatal) meningiomas operated in our institute from January 1990 until February 2008, 25 patients were operated through an anterolateral/lateral (subtemporal/anterior traspetrosal ) route with an operative mortality of 7%. While the tumor resection was carried out through a combined posterior subtemporal/pre- or transsigmoid (posterior petrosal) in 22 cases (26%), it was through a retrosigmoid supraparacerebellar route in 35 cases (40%). In three cases with extracranial extension to the infratemporal area, a modified Fisch approach was used. An operative video of the anterior transpetrosal approach will be presented and the technical details highlighted. The anterior transpetrosal approach provides an excellent approach for petroclival meningiomas with middle fossa and upper clival extension.

Temporal mediobasal tumors: a proposal for classification according to surgical anatomy

Development of a classification for temporal mediobasal tumors based on anatomical and neuroradiological aspects to help evaluate surgical accessibility and risk. Preoperative magnetic resonance imaging, surgical approaches and outcomes of 235 patients with a temporal mediobasal tumor were analyzed retrospectively. Surgical landmarks were defined in accordance with operative anatomy. Previous classifications of these tumors were reviewed and a new classification system was developed. The new classification system recognises four types of temporal mediobasal tumor based on anatomical landmarks, location, and size. Type A comprises lesions confined to the uncus, hippocampus, parahippocampus, and/or amygdala. Type B comprises lesions in the area immediately lateral to the structures where type A tumors are located but sparing lateral gyri. Type C tumors are larger lesions, which occupy the area of type A and type B simultaneously. Type D tumors originate from the temporal mediobasal region and invade into the adjacent structures of the temporal stem, insular cortex, claustrum, putamen, or pallidum. The area occupied by a tumor in the axial plane was divided into anterior (a) and posterior (p) subregions. Progressive grading from A to D and from "a" to "p" was based on the view that larger and more posteriorly growing tumors were more difficult to remove. Lesions located in the anterior subregion (n = 173) were easier to remove by the transsylvian route (39%) or after partial anterior lobectomy (32%). For the posterior lesions (n = 62), a subtemporal approach was more appropriate (75%). Based on a series of 235 temporal mediobasal tumors, a classification system was designed to aid in decision making about operability, surgical risk, and approach.