Presigmoid Approach Research Articles

Abordaje multidisciplinar al tumor de saco endolinfático

Papilar adenocarcinoma of endolymphatic sac is related with Von Hippel Lindau disease at 15% of cases, has a slow growing with a high local aggressiveness, and doesn't metastasize. It causes symptoms of Meniere's syndrome due to the compression that produces at endolymphatic duct. When it presents with hearing loss is usually sudden and irreversible manner. The diagnostic is made with image tests and analysis of its structure with immunohistochemical tests. The elective treatment is surgical remove, and its main complication the perioperative bleeding it can be avoided with preoperative embolization or stereotactic radiation. A case of endolymphatic sac tumour is presented, in a 17-years-old male with unilateral deafness and crisis of rotate vertigo, with family history of Von Hippel-Lindau disease. Perceptive deafness and right vestibular arreflexia are detected at technical exploration. In a petrous bone computer tomography appears a mass at vestibular aqueduct. We performed a petrosectomy with presigmoidal approach and saving of inner ear. Pathological analysis revealed an endolymphatic sac tumour. In patients with a family history of Von Hippel Lindau disease and clinical symptoms of vertigo and normal hearing or with slight hearing loss we should suspect the presence of endolymphatic sac tumor. The clinical presentation of hearing loss can be sudden and irreversible even with negative or inconclusive images. Therefore, a quick action is important for the preservation of this function.

The presigmoid approach for removal of tumours causing ventral compression of the brainstem. Surgical results and postoperative quality of life

Objective. To assess surgical results and quality of life after removal of tumours causing ventral compression of the brainstem using the presigmoid or combined presigmoid/retrosigmoid approaches.Methods. A review of all our patients operated on with removal of tumours causing ventral compression of the brainstem in whom either the presigmoid or combined presigmoid/retrosigmoid approaches were used. Post-operative quality of life was assessed using the SF-36 questionnaire.Results. A total of 12 consecutive patients were included. A favourable complication profile was found. Cerebrospinal fluid leakage and secondary hydrocephalus were the most frequent complications. Post-operative scores from Karnofsky Performance Scale and ECOG after median 24 months were median 85 and 1, respectively, representing ability to carry on daily activities. Nevertheless, quality of life as assessed subjectively by SF-36 showed significantly reduced values as compared with normative values from Norwegian population.Conclusions. We found favourable surgical results when using the presigmoid approach alone or combined with the retrosigmoid route for large-sized extrinsic tumours causing ventral compression of the brainstem, both regarding complication profile, degree of tumour removal and functional outcome. However, impact of disease and surgery on quality of life appears to be more significant when assessed subjectively by the patients.

The presigmoid approach to anterolateral pontine cavernomas

Anterolateral cavernomas of the pons have been surgically removed via a variety of approaches, commonly retrosigmoid or transventricular. The goal in this study was to evaluate the presigmoid approach as an alternative. Clinical data were reviewed in 9 patients presenting with anterolateral pontine cavernomas between 1999 and 2007. All patients were treated via a presigmoid approach, which provided a nearly perpendicular trajectory to the anterolateral pons. The brainstem was entered through a "safe zone" between the trigeminal nerve and the facial/vestibulocochlear nerve complex. Complete resection was achieved in all cases. No patient experienced recurrent events during follow-up (1-24 months). The patients' modified Rankin Scale score improved within 1 year of surgery (1.7 ± 0.4) compared with baseline (2.6 ± 0.2; p < 0.05). Only one patient experienced a new deficit (decreased hearing), which was corrected with a hearing aid. The presigmoid approach is recommended for the resection of anterolateral pontine cavernomas. With this approach, the need for cerebellar retraction is nearly eliminated. The lateral "presigmoid" entry point creates a trajectory that allows complete resection of even deep lesions at this level, or anterior to the internal acoustic meatus.

Postauricular, transpetrous, presigmoid approach for extensive skull base tumors in the petroclival region: the successes and the travails

Postauricular, transpetrous, presigmoid approach combines a supra/infratentorial exposure with partial petrosectomy to access third to the twelfth cranial nerves and extraaxial lesions situated anterolateral to brainstem. It provides a shorter working distance to large petrosal, petroclival, cerebellopontine, and cerebellomedullary cisternal lesions and their extensions to the subtemporal-infratemporal areas. This study reviews the surgical technique, corridors of extension, and complications encountered utilizing this approach for excising extensive lesions in these locations. The lesions (n = 14) included petroclival meningiomas [(n = 5), including three recurrent lesions], dumbbell lower cranial nerve schwannomas (n = 2), giant acoustic schwannomas (n = 2), recurrent giant trigeminal nerve schwannoma (n = 1), glomus jugulare (n = 3), and recurrent petrous aneurysmal bone cyst (n = 1). The approach was combined with a retrosigmoid suboccipital craniectomy (n = 3), with an infratemporal approach (n = 2), and with an extreme lateral transcondylar approach and a translabyrinthine approach in one patient each, respectively. External auditory canal was not ligated in nine patients, superior petrosal sinus and tentorial division was performed in all patients, and sigmoid sinus-internal jugular vein was excised in three patients (with a glomus jugulare (n = 1) and petroclival meningioma (n = 2), respectively). Repair was performed with fat-fascia, pedicled pericranium, and temporalis muscle. Lumbar drain was placed for three to five postoperative days. Total excision was performed in nine patients. Small tumor remnants were left attached to the brainstem (n = 3, petroclival meningioma), carotid canal and cavernous sinus (n = 1, glomus jugulare), and sigmoid sinus-jugular bulb (n = 1, recurrent trigeminal schwannoma). A two-staged procedure was performed in three patients. Two patients with recurrent giant petroclival meningiomas died: one with lower cranial nerve paresis due to aspiration pneumonitis and the other with cerebrospinal fluid otorrhoea and secondary meningitis. The approach facilitates direct tumor decompression and its retraction away from the brainstem without initially encountering the intracisternal cranial nerves and neuraxis. It provides multiple corridors for excising extensive posterior fossa tumors. Preoperative assessment of sigmoid sinus dominance, jugular bulb height, labyrinth, vein of Labbe, and space available through Trautman's triangle considerably helps in complication avoidance.

Surgical management of petroclival meningiomas invading into cavernous sinus

To analyze the clinical features, surgical strategy and management outcomes of petroclival meningioma invading into cavernous sinus. Fifteen cases with petroclival meningioma invading into cavernous sinus were retrospectively analyzed. The presigmoidal approach was selected to remove tumors. The surgical strategy for tumor in cavernous sinus was partial resection combined with radiosurgery. Postoperative cranial nerve function and patient survival status were analyzed. The main symptoms of subtype of petroclival meningiomas were headache, abducens nerve palsy and trigeminal neuropathy. Gross total tumor removal was achieved in 13 cases and more than 90% resection in 2 cases. There was no operative death. Nine cases suffered from new postoperative cranial nerve deficits. After a follow-up of 6 - 59 months, complete improvement was achieved in oculomotor nerve deficits, much improvement in VII nerve deficit, but V and VI nerve function deficits improved slightly. The tumor progression-free survival rate was 86.7%. Rational surgical strategy to petroclival meningiomas invading into cavernous sinus should be suggested to reduce the operative morbidity and improve the survival quality of these patients.

Two-bone flap craniotomy for the transpetrosal–presigmoid approach to avoid a bony defect in the periauricular area after surgery on petroclival lesions: technical note

The authors describe a two-bone-flap craniotomy technique to avoid the bone defect caused by the transpetrosal-presigmoid approach. Briefly, this technique includes three steps. The first step is to elevate a temporoparietal bone flap located superiorly to the transverse and sigmoid sinuses. The second step is to dissect the transverse and sigmoid sinuses away from the bone by inserting a gelatin sponge. This maneuver provides hemostasis and protects the sinuses from injury. The third step is to cut a second bone flap including part of the temporal bone and the outer table of the mastoid bone with a high-speed drill system. After the operation, the two bone flaps are fixed in place with titanium osteosynthesis fixation material. This approach provides a simple, easy, and safe technique for the transpetrosal-presigmoid approach. The technique has been performed in 83 patients treated for petroclival neoplasms with excellent cosmetic results.

Meningioma arising in Werner syndrome, a case report and literature review

Objective To report a case of Werner syndrome with meningioma in cavernous sinus and clivus, and review the relative literatures. Methods A pre-sigmoid sinus approach was performed for the meningioma, and we analyzed the genome sequence of the patient. Results According to her clinical features and result of genetic test of WRN, she was diagnosed as Werner's syndrome. The meningioma was totally removed. Conclusions This is the first case of Werner syndrome with meningioma in Chinese, we should emphasize further study of the associated genes of Werner syndrome and clinical manifestation. Key words: Meningioma; Werner syndrome; Gene

Quantitative Analysis of Surgical Exposure and Angle of Surgical Freedom Obtained by Endoscope and Microscope in the Retrosigmoid and Various Posterior Petrosectomy Approaches to the Petroclival Region Using CT-Based Frameless Stereotaxy

Objective: Several approaches are used to expose the petroclival region and most of them require a certain degree of temporal bone resection with its associated approach morbidity, such as hearing and facial nerve compromise. To gain insight into the benefits of integration of endoscopy, we evaluated and compared the exposure obtained by endoscope and microscope in the retrosigmoid and the presigmoid approaches by quantitative analysis.

Neurovascular compression of the abducent nerve causing abducent palsy treated by microvascular decompression

Isolated abducent palsy is a symptom that can be caused by many different intracranial pathological conditions. In this report the authors describe the case of a patient who suffered isolated abducent palsy resulting from vascular compression of the sixth cranial nerve; surgical treatment consisted of microvascular decompression (MVD). This 56-year-old man presented with short-lasting episodes of a pulling sensation at the lateral side of his right eye associated with intermittent diplopia, followed by a progressive palsy of the abducent nerve and constant diplopia. Magnetic resonance imaging revealed a neurovascular contact of a dolichoectatic basilar artery with the abducent nerve. The patient underwent surgery consisting of a combined supra- and infratentorial presigmoid approach and subsequent MVD of the abducent nerve. Postoperatively, the abducent nerve palsy resolved within days, and the patient remains free of symptoms with a follow-up time of 4 years. This is the first report of a neurovascular compression of the abducent nerve treated successfully by MVD.

Motor evoked potential mapping and monitoring by direct brainstem stimulation

✓Motor evoked potentials (MEPs) by direct brainstem stimulation were generated during 12 neurosurgical operations performed in five posterior fossa tumors, six vertebrobasilar aneurysms, and an arachnoid cyst. The anterior aspect of the brainstem was exposed using a subtemporal approach (in six cases), a presigmoid approach (one case), or a lateral suboccipital approach (five cases). A train of five monopolar 5 to 25 mA pulses was then applied, and MEPs were recorded from the extremities. Motor evoked potentials were recorded in all patients (four mappings and seven monitorings) except in a 12-year-old child who underwent surgery for a posterior cerebral artery aneurysm. Although he experienced postoperative motor palsy, the aneurysm ruptured before electrodes could be placed. Two patients with postoperative motor palsy, one with a clival meningioma and one with a basilar trunk aneurysm, had shown significant decreases in MEP amplitude and even complete disappearance of MEPs during intraoperative brainstem stimulation. Motor evoked potentials elicited by direct brainstem stimulation seem to be an accurate neurophysiological monitoring method during operations around the anterior and lateral aspects of the brainstem.

Motor evoked potential mapping and monitoring by direct brainstem stimulation

Motor evoked potentials (MEPs) by direct brainstem stimulation were generated during 12 neurosurgical operations performed in five posterior fossa tumors, six vertebrobasilar aneurysms, and an arachnoid cyst. The anterior aspect of the brainstem was exposed using a subtemporal approach (in six cases), a presigmoid approach (one case), or a lateral suboccipital approach (five cases). A train of five monopolar 5 to 25 mA pulses was then applied, and MEPs were recorded from the extremities. Motor evoked potentials were recorded in all patients (four mappings and seven monitorings) except in a 12-year-old child who underwent surgery for a posterior cerebral artery aneurysm. Although he experienced postoperative motor palsy, the aneurysm ruptured before electrodes could be placed. Two patients with postoperative motor palsy, one with a clival meningioma and one with a basilar trunk aneurysm, had shown significant decreases in MEP amplitude and even complete disappearance of MEPs during intraoperative brainstem stimulation. Motor evoked potentials elicited by direct brainstem stimulation seem to be an accurate neurophysiological monitoring method during operations around the anterior and lateral aspects of the brainstem.

Retrosigmoid Approach to Ventrolateral Pontine AVM

There are a number of different surgical approaches to pontine lesions, such as the anterior transpetrosal (Kawase's) approach, lateral (presigmoid) approach, and rhomboid fossa approach. The anterior transpetrosal approach is only suitable for exophytic lesions and the rhomboid fossa approach is problematic because of the possible damage to neural structures in its path. Yoshitusugu Oiwa et al reported on the removal of a pontine lesion through the presigmoid approach in which the lateral surface of the pons is approached through a small window without any additional neurologic deficit. The authors report on the successful removal of a pontine AVM (intra-axial) situated on the rostral part of the pons (lateral pontine surface) between the CN V and VII-VIII complex through a conventional retrosigmoid approach using a small lateral incision. The patient complained of sudden-onset headache and right-sided hemiparesis; brain CT showed hematoma on the left ventrolateral pons. There was sudden decreased consciousness on the fifth day of admission and follow-up showed rebleeding on the site. After transfemoral cerebral angiography and brain MRI, the hematoma and lesion were removed via a left-sided retrosigmoid approach. The lesion was confirmed as a pontine AVM. The patient recovered consciousness on the fifth postoperative day and showed signs of dense right-sided hemiparesis, diplopia, central-type facial palsy (left), and hearing loss. Exams at 15 months postoperatively showed full recovery of diplopia with near normal recovery of hemiparesis and facial palsy, but the hearing deficit was not improved. The important neural structures of the pons are (1) the corticospinal tract in the ventral pons, (2) reticular formation in the central pons, and (3) most of the nucleus in the dorsal part of the pons (rhomboid fossa). The middle cerebellar peduncle is in the lateral pons but a small incision on the peduncle results in only transient aggravation of cerebellar ataxia, so a surgical approach through the lateral pontine surface is feasible, which makes the conventional retrosigmoid approach a excellent choice in that area.

Anatomic study of the supra-infratentorial presigmoid partial labyrinthectomy keyhole approach assisted by neuro-navigation

To design a new supra-infratentorial presigmoid partial labyrinthectomy keyhole approach assisted by neuro-navigation system, and to explore the possibility of removing the approach-correlated bone precisely. Navigation data were established on 8 cadaveric heads fixed by formalin and perfused intracranial vessels with colored silicone. Before the operation, the important structures were outlined with different colors in the navigation system. A 7-cm "C" shape skin incision was performed 1cm behind the helix. On elevating the skin flap and musculofascial flap respectively, a 3.5 cm x 3 cm bone window was performed. After skeletonized the sigmoid sinus, bony labyrinth and the canal for facial nerve assisted by neuro-navigation, the amount of dura exposed and the maximal angle of vision were measured before and after partial labyrinthectomy with petrous apicectomy, the anatomic structures were observed as well. The incision of the supra-infratentorial retrolabyrinthine keyhole approach fully met the needs of the presigmoid partial labyrinthectomy keyhole approach. The approach-correlated bone could precisely be drilled with the aid of neuro-navigation, which could avoid the bewilder in drilling process. This approach provided wide exposure to petroclival region, cerebellopontine angle, prepontine region and posterior cavernous sinus. After partial labyrinthectomy with petrous apicectomy, the horizontal exposure was increased to (18.8 +/- 1.6) mm (left side) and (17.7 +/- 1.2) mm (right side); the maximal angle of vision was increased to (59.3 +/- 9.2) degrees (left side) and (57.0 +/- 11.0) degrees (right side); the vertical exposure increased (10.0 +/- 1.0) mm (left side) and (10.0 +/- 0.8) mm (right side); there were significant differences between before and after partial labyrinthectomy with petrous apicectomy (P < 0.01). It is feasible to perform the supra-infratentorial presigmoid partial labyrinthectomy keyhole approach. The exposed field and the maximal angle of vision can be obviously increased by partial labyrinthectomy with petrous apicectomy.

Endolymphatic sac carcinoma of the right petrous bone in Von Hippel–Lindau disease

A large endolymphatic sac papillary adenocarcinoma in a patient with Von Hippel–Lindau (vHL) disease is reported. A 31-year-old man was treated for a left eye retinal angioma 10 years previously and had been blind in that eye since. He was admitted with progressive tinnitus, lower cranial nerve paresis and ataxia. Investigations revealed a vascular and bone-eroding petrous tumour. The entirely extradural tumour involved a large part of the petrous bone and extended into the cerebellopontine angle. The vascular tumour was radically resected using a presigmoid approach after feeding vessel embolisation. The literature on this rare clinical entity is briefly discussed.

Microsurgical Excision of the Large or Giant Cerebellopontine Angle Meningioma

The object of this study was to analyze the therapeutic effects of microsurgical excision in cases with the large or giant cerebellopontine angle meningioma. We retrospectively analyzed the 56 patients who suffered from the large or giant cerebellopontine angle meningioma and underwent the microsurgical therapy, for which the suboccipital-retrosigmoidal approach was adopted in 38 cases, the temporal-occipital craniotomy, presigmoidal approach in 6 cases, the temporal-occipital craniotomy, inferotemporal tentorium cerebelli approach in 8 cases, and the temporal-occipital craniotomy, supratentorial or infratentorial allied approach in 4 cases. The tumors of 44 cases were all resected (Simpson I, II), with a total resection rate of 78.6%, and there was no operative mortality. After surgery, symptoms improved in 40 cases and remained unchanged in 10 cases. Among 54 cases, recrudescence was seen in 2 cases (3.7%) and being able to take care of themselves in 50 cases (92.6%) at 6 months through 6 years follow-up after surgery. A rationally selected surgical approach, a microscopic technology applied in the operation to appropriately treat and protect vein, nerve and brain stem, which can ideally excise the tumors, together can increase the survival ability of patients.

Skull Base Approaches for Complex Vertebrobasilar Aneurysms

Purpose: The authors' experience in the treatment of vertebrobasila (VB) aneurysms has been revised. Different skull base approaches were used based on the location, size, and morphological features of the lesions. The rationale of the choice of each approach is discussed. Method: One hundred twenty-eight patients harboring 135 VB aneurysms were operated on in 15 years. Of these lesions, 18% were giant. Different approaches have been used. The majority of patients harboring distal basilar artery aneurysms underwent an extended pterional approach; the exposition of lesions located below the posterior biclinoidal line required a transcavernous route. Most complex lesions were treated through a cranio-orbitary approach. Most middle basilar artery aneurysms were treated through a retrolabyrinthine petrosal presigmoid approach; for more complex lesions a combined transpetrosal approach was used. Aneurysms of the inferior third of the basilar trunk and of the VB junction were operated on by a high posterolateral approach. Distal vertebral lesions were treated through an inferior posterolateral approach. The subtemporal approach was performed for lesions located distally in the PCA or in the SCA. The retrosigmoid approach was used for lesions of distal AICA or PICA. Result: Skull base approaches allow the best lesional control and handling in the surgical treatment of complex VB aneurysms, providing straight access, wide working room, short working distance, and lesional control from different angles with minimal retraction or manipulation of critical neurovascular structures. These approaches give complete vascular control allowing the exposure of the parent and efferent vessels (to achieve temporary occlusion), the exposure of the complete implant base (to obtain the best dip positioning), and a wide exposure of the sac (to manipulate it from different angles). Conclusion: The treatment of VB aneurysms is challenging because these lesions are deeply located in very limited subarachnoid spaces, in intimate relationship with the brainstem and its vasculature. VB aneurysms present special intrinsic features (prevalence of large and giant lesions with frequent presence of intraluminal thrombosis and of atherosclerotic changes of sac and parental artery), that make the endovascular treatment ineffective, especially in complex cases, so that surgery remains the best therapeutic option. The application of any helpful technical and methodological resource, surgical or alternative, is required to achieve optimal results.

Surgical treatment of a basilar perforator aneurysm not accessible to endovascular treatment

Aneurysms originating from perforatoring branches of the midbasilar artery are extremely rare. Rupture of such an aneurysm resulted in a subarachnoid hemorrhage with a prepontine clot in a 44 year old male who presented with an acute confusional state. After coil embolization had failed, the partially thrombosed aneurysm was wrapped and coagulated via a combined supra-/infratentorial subtemporal presigmoid approach in prone position. The postoperative course was complicated by a tension pneumatocephalus and liquorrhea. Additional aneurysms of the anterior communicating artery and right middle cerebral artery were clipped several months later. The patient recovered well, and except for slight gait ataxia no other deficit remained.

Facial and Cochlear Nerve Function after Surgery of Cerebellopontine Angle Meningiomas

Meningiomas of the cerebellopontine angle (CPA) share a common location, but their site of dural origin and their relationship to surrounding neurovascular structures of the CPA are variable. The clinical presentation and outcome after surgical resection are different because of the diversity of this tumor entity. We report on a series of 421 patients with CPA meningiomas, with special emphasis on the analysis of the preoperative and postoperative facial and cochlear nerve function in relation to the site of dural attachment and main tumor location in the CPA cistern. Among 421 patients, the charts of 347 patients with complete clinical data, including the history and audiograms, imaging studies, surgical records, discharge letters, histological records, and follow-up records, were reviewed retrospectively. Data about preoperative and postoperative facial nerve function were available in 334 patients, and audiometric analysis was conducted in 333 patients. Patients with neurofibromatosis Type 2 were excluded from the study. There were 270 women and 77 men, with a mean age of 53.4 years (range, 17.6-84 yr). Among these patients, 32.9% of the tumors originated at the petrous ridge anterior to the inner auditory canal (IAC) (Group 1), 22.2% showed involvement of the IAC (Group 2), 20.2% were located superior to the IAC (Group 3), 11.8% were inferior to the IAC (Group 4), and 12.9% were posterior to the IAC, originating between the IAC and the sigmoid sinus (Group 5). Patients presented with disturbance of Cranial Nerves V-VIII, the lower cranial nerves, and ataxia, depending on the main tumor location. Tumor resection was performed through a suboccipital-retrosigmoidal approach in the semisitting position in 95% of the patients. A combined supratentorial-infratentorial presigmoidal approach was performed in 5%. Total tumor removal (Simpson Grade 1 and 2) was achieved in 85.9% and subtotal removal in 14.1%. The best initial postoperative facial and auditory nerve function was observed in tumors belonging to Groups 3 and 5. Recovery from preoperative deafness was observed in 1.8% of patients. On long-term follow-up, good facial nerve function (House-Brackmann Grade 1 or 2) was observed in 88.9% of patients. Hearing preservation among patients with preoperative functional hearing was documented in 90.8% on long-term follow-up. Although the outcome of facial and cochlear nerve function is different in CPA meningiomas, depending on the topographic classification of these tumors, preservation of the cochlear nerve is possible in every tumor group and should be attempted in every patient with CPA meningioma. It has to be kept in mind that recovery of hearing was also observed in patients with preoperative profound hearing deficits.

Commentary

BACKGROUNDPetroclival meningiomas represent a difficult surgical challenge. The introduction of modern techniques of skull base surgery has stimulated the interest of the neurosurgical community in the surgical management of these lesions, although very good results have been obtained by experienced neurosurgeons in cases of petroclival meningioma operated using traditional surgical approaches.METHODSThirty-one cases of petroclival meningioma have been operated on during a 4-year period using two different philosophies as far as the approach. Group A patients (13 cases) have been operated on using mostly either a subtemporal transtentorial or a retrosigmoid approach. Group B patients (18 cases) have been managed using a lateral skull base approach, either the anterior transpetrosal or the presigmoid approach. Translabyrinthine/transcochlear approaches have been used occasionally.RESULTSTumor dissection and removal seemed to be easier in skull-base operated patients. However, operations take longer and surgical complications such as cerebrospinal fluid leak and hearing loss were increased. Radical tumor removal could be achieved in an equal percentage of cases of both groups (77% vs 83%). The early postoperative course was more favorable in group B patients. However, late permanent morbidity appeared to be similar in the two groups of patients.CONCLUSIONSSkull base approaches facilitate tumor dissection and removal at the expense of increased surgical complications. However, the widened surgical field and increased angle of approach that the techniques of skull base surgery may offer can play a significant role in the removal of sizeable, infiltrative, and/or recurrent petroclival meningiomas.

Pitfalls in surgery of meningeomas of the free tentorial edge.

Clinical experiences from 15 meningeomas located on the free edge of the tentorium are reported. Unexpected findings and complications found in five patients are presented in detail: Despite successful removal without postoperative morbidity after a presigmoid approach the preoperative loss of function of the ophthalmic nerve may cause increasing keratitis, which may result in blindness over the years after surgery. Before a presigmoid approach is performed, angiography or magnetic resonance angiography is advised, because the patient may have only one sigmoid sinus on the tumor side. An acute subdural hematoma as a complication of surgery may not only occur after, but also during surgery with the patient in the semi-sitting position. When a space occupying tumor of the tentorium is discovered, there may be an additional spinal one. If total removal of an extensive tumor of the free edge of the tentorium appears too hazardous, a two-stage strategy with a one year interval may lead to success.