Arachnoid Plane Research Articles

Anterior Microsurgical Approach to Ventral Lower Cervical Spine Meningiomas: Indications, Surgical Technique and Long Term Outcome.

Ventral lower cervical spinal meningiomas with posterior displacement of the spinal cord are rare and anterior approach has been rarely reported in the literature. The authors present their experience about eight patients operated through anterior microsurgical approach. Exposure of meningiomas was achieved through one or two corpectomies, according to meningioma extension. Tumour removal was performed thanks to the aid of a dedicated ultrasonic aspirator, and intraoperative evoked potentials were employed. Particular care was taken with the materials adopted for reconstruction of the anterior dural plane, to avoid postoperative cerebrospinal fluid leak. Vertebral fusion and stabilization were achieved by tantalum cage or titanium graft in case of one or two corpectomies respectively; anterior titanium plate fixed with screws was applied in all patients. Extent of tumour removal was related to the presence of a conserved arachnoidal plane between the tumour and the spinal cord: total removal was achieved in 2 patients, while gross total removal in the other six ones. Postoperative neurological outcome, which was favourable in all patients, was related mostly to preoperative neurologic status. No recurrence after total removal and no remnant growth after gross total removal occurred during an average follow-up period of 6, 7 years.

Prognostic Significance of Peritumoral Edema in Patients With Vestibular Schwannomas.

Peritumoral edema (PTE) in skull base meningiomas correlates to the absence of an arachnoid plane and difference in outcome. In vestibular schwannomas (VS), PTE and its significance for microsurgery and outcome have never been systematically evaluated. To evaluate whether PTE correlates with tumor characteristics, the presence of an arachnoid plane, and outcome. A retrospective study of the institutional database. PTE was evaluated on fluid-attenuated inversion recovery magnetic resonance images. Preoperative patient data and intraoperative tumor features (presence of tumor pseudocapsule, vascularity, degree of adhesion/invasion of the arachnoid) were noted. Outcome measures were completeness of removal, neurological outcome, and complication rate. These parameters in patients with PTE (group A) were correlated to those in matched series without edema (group B). Thirty patients presented with PTE (5%). The mean VS size was 3.4 cm. No major differences in the degree of adhesion or presence of an arachnoid plane were found. VS with PTE were more frequently hypervascular (26.7% in group A vs 6.7% in group B). The presence of PTE in VS was not related to surgical radicality. VS with PTE had worse early postoperative facial nerve function, but at 12 months, there was no major difference. VS with PTE were prone to cause postoperative hemorrhages in the tumor bed. PTE in VS does not correlate with the degree of tumor adhesion and the presence of an arachnoid dissection plane. The radicality of tumor removal and long-term functional outcome in patients with and without PTE was similar. VS with PTE are more vascular and prone to cause postoperative hemorrhages. Therefore, meticulous hemostasis is advisable.

Retrosigmoid approach for resection of petroclival meningioma

This video describes the classic retrosigmoid approach for the resection of petroclival lesions. In this procedure, a careful dissection of the tumor within the arachnoid plane from the neurovascular structures is described. The key steps in the procedure are outlined, and include positioning, tumor devascularization, decompression, dissection from lower cranial nerves, IV, V cranial nerves and the VII-VIII complex and from the brainstem and closure of the dura, bone flap and the incision. The video can be found here: http://youtu.be/DmutL7dBOxI .

Anterior Microsurgical Approach to Ventral Lower Cervical Spine Meningiomas: Indications, Surgical Technique and Long Term Outcome.

Ventral lower cervical spinal meningiomas with posterior displacement of the spinal cord are rare and anterior approach has been rarely reported in the literature. The authors present their experience about eight patients operated through anterior microsurgical approach. Exposure of meningiomas was achieved through one or two corpectomies, according to meningioma extension. Tumour removal was performed thanks to the aid of a dedicated ultrasonic aspirator, and intraoperative evoked potentials were employed. Particular care was taken with the materials adopted for reconstruction of the anterior dural plane, to avoid postoperative cerebrospinal fluid leak. Vertebral fusion and stabilization were achieved by tantalum cage or titanium graft in case of one or two corpectomies respectively; anterior titanium plate fixed with screws was applied in all patients. Extent of tumour removal was related to the presence of a conserved arachnoidal plane between the tumour and the spinal cord: total removal was achieved in 2 patients, while gross total removal in the other six ones. Postoperative neurological outcome, which was favourable in all patients, was related mostly to preoperative neurologic status. No recurrence after total removal and no remnant growth after gross total removal occurred during an average follow-up period of 6, 7 years.

Predictive factors related to symptomatic venous infarction after meningioma surgery

Introduction. The incidence of venous infarction after surgical resection of meningioma is low, but its occurrence can necessitate additional surgical procedures and long hospital stay. In this study, we evaluated variables associated with venous infarction after meningioma surgery. Methods. Among 825 patients with intracranial meningiomas who underwent microsurgical resection between January 1993 and March 2011, 27 (3.3%) presented with neurological deterioration due to postoperative venous infarction. The following factors were included in the statistical analysis to determine their association with venous infarction: sex, age, location, relation to venous sinus, peritumoural oedema, size and degree of resection. Results. Incidence of venous infarction was 6.8% with large meningiomas (size ≥ 4 cm), but with small (size < 4 cm) was reduced to 1.2% (p < 0.001). Meningiomas with perilesional edema elicited venous infarction more frequently than those without (5.1% vs. 2.3%, p = 0.030). Venous infarction was also determined to occur at 5.5% frequency in superficial meningiomas, such as parasagittal, falx and convexity, but only at 0.5% frequency in deep locations (p = 0.001). Venous infarction additionally occurred less often in meningiomas at a distance from the midline venous sinus than in those nearby, such as parasagittal and falx (2.2% vs. 6.6%, p = 0.004). Conclusions. To prevent venous infarction after meningioma surgery, it is essential to maintain the intervening arachnoid plane as much as possible; this is especially important in meningiomas larger than 4 cm, combined with peritumoural edema or positioned superficially around the midline venous sinus.

Anterior Interhemispheric Approach for Tuberculum Sellae Meningioma

The tuberculum sellae meningioma (TSM) arises from the tuberculum sellae, chiasmatic sulcus, and limbus sphenoidale. To retrospectively analyze patients with TSM who underwent surgery via an anterior interhemispheric approach, with special attention to visual outcomes. Nine consecutive patients between April 2004 and December 2009 were examined. Visual impairment score (VIS) was used to analyze the visual status of the patients. A VIS is the sum of the scores in specific tables for visual acuity and visual field defects. Visual status was sequentially evaluated in the preoperative period and within 2 weeks of the operation. Any change in the VIS was considered an improvement or deterioration of visual function. All tumors were removed via an anterior interhemispheric approach. Following the wide dissection of the interhemispheric fissure, the tumor was first detached from its origin and debulked with the ultrasonic aspirator starting at the midline. The debulking continued until the arachnoid plane separating the nerve and tumor was visualized. Gross total resection (Simpson I + II) was achieved in all 9 patients. The average VIS was 56.1 in the preoperative period and 26.3 in the postoperative period. Among 9 patients, 8 patients had an improvement of the VIS after surgery. VIS was unchanged in 1 patient, and no patients experienced visual deterioration. Other nonvisual complications, such as rhinoliquorrhea, venous infarction, and permanent anosmia, occurred in 3 patients. Despite the small number of patients, a high resection rate and favorable visual outcome support the suitability of this approach for resection of TSM.

Meningiomas del surco olfatorio. Tratamiento microquirúrgico radical por vía bifrontal

To describe the microsurgical technique for the radical removal of olfactory groove meningiomas through the bifrontal approach. To review the diagnostic elements to be taken into account in the selection of the surgical approach to these tumours. A microsurgical series of 35 olfactory groove meningiomas operated on through a bifrontal craniotomy is reviewed. The mean tumoral volume was 85cc (4.4cm diameter). A relevant peritumoral brain edema was found in 65.7% of cases, hyperostosis in the implantation base in 80% and paranasal sinus invasion in 28.6%. A Sipmson grade 1 resection was achieved in every case. A patient died due to a postoperative pneumonia. Postoperative hospitalization time was between 3 and 20 days and at discharge all patients had a Glasgow Outcome Scale grade 4-5. The mean follow-up was 55.2 months. Two patients had postoperative transient rhinolicuorrhea and an additional patient developed hydrocephalus. An asymptomatic recurrence have been identified in a patient four years after surgery. In our experience the bifrontal approach allowed the radical removal of huge olfactory groove meningiomas. The microdissection of the anterior cerebral artery A2 segments is possible thanks to the arachnoidal plane between vessels and tumor. Tumoral blood flow is secured by the early approaching of the base of the tumor and preoperative embolization is not necessary. Bifrontal approach allows an aggressive treatment of the hyperostosis, bone infiltration and paranasal sinus invasion. Anterior fossa reconstruction is done using a vascularized periosteal flap.

Hyperostosing meningiomas of the cranial vault with and without tumor mass

This study represents the first clinical series in the reported literature exclusively concentrating on the clinicoradiological features of non-sphenoidal hyperostosing meningiomas. It attempts to identify the factors that may have an impact on the surgical strategy and results of this unique subgroup of meningiomas. In the vault, we distinguished between meningiomas with and without tumor mass according to their thickness (<1.5 vs ≥ 1.5 cm) and between convexity (lateral) and calvarial (midline) meningiomas according to their location. The clinical, radiological, surgical and prognostic characteristics of the tumors were examined. Over a 10-year period, we observed 24 cases, 18 of which in the convexity (nine without and nine with tumor mass) and six calvarial (one without and five with tumor mass). Six patients presented with neurological signs, while the majority showed bony hyperostosis (n = 19). Brain edema (n = 7) was found only in cases with tumor mass, in all neurologically impaired patients, and only in one intact patient. Total removal was obtained in 92% patients. Small residual tumors attached to the superior sagittal sinus and perisinusal dura were coagulated in situ and not excised. Morbidity occurred in three symptomatic patients with tumor mass and brain edema (mental confusion in one case and hemiparesis in two cases). Mortality was nil. After a mean follow-up of 4.8 years, three cases relapsed, all of which had initially presented with atypical meningiomas. The rare hyperostosing cranial vault meningiomas may be classified as being with and without tumor mass. A number of categorical differences exist in their distribution, pattern of hyperostosis, surrounding arachnoidal plane, and their prognosis. Careful preoperative planning aimed at tailoring the extent of tumor removal and reconstruction in the neighboring infiltrated structures enables a good outcome to be achieved.

Tentorial Meningiomas

Three-dimensional understanding of the pathologic and radiologic anatomy of tentorial meningiomas is the basis for our proposed classification, which provides the rationale for surgical approach for each tentorial location. Safe resection is the surgical goal, whether gross or subtotal resection is used. For each group of tentorial meningioma classified (anterior incisural, middle incisural, falcotentorial, posterolateral and posteromedial, torcular) and the subtypes, consideration is given to the optimal surgical corridor. Particular topics discussed include careful interpretation of the preoperative venous sinus to determine the extent of tumor involvement; devascularization, debulking, and dissection of the tumor with preservation of the arachnoidal plane; and resection of the dural origin as completely as possible.

Dural Cavernous Hemangioma of the Cerebellar Falx -Case Report-

A 47-year-old man presented with a rare case of dural cavernous hemangioma of the cerebellar falx incidentally detected as a mass lesion in the posterior cranial fossa. Neurological examination revealed no deficits or physical symptoms. Computed tomography demonstrated a well-demarcated hyperdense mass, with no calcification, in the cerebellar vallecula. Magnetic resonance imaging showed the extra-axial mass as homogeneously isointense on T(1)-weighted images, and hyperintense on T(2)-weighted images, compared to the adjacent cerebellar parenchyma that had no hypointense halo. The cerebellar vermis was slightly compressed ventrally, the adjacent brain parenchyma was not swollen, and there was no evidence of hydrocephalus. The mass and the attached cerebellar falx were homogeneously enhanced by contrast medium. The dural enhancement was considered a dural tail. No other intracranial vascular malformations were found. The preoperative diagnosis was posterior cranial fossa meningioma attached to the cerebellar falx. Median suboccipital craniotomy exposed the reddish mass attached to the cerebellar falx. The arachnoid plane was well preserved. Total en bloc resection was performed with minimal blood loss. The postoperative course was unremarkable. The resected mass had a reddish-brown mulberry appearance, with spongy cross section with multiple blood-filled spaces. Histological examination identified dilated blood-containing channels lined with flattened endothelium and separated by fibrous tissue, but no luminal thrombus or hemorrhage. The histological diagnosis was dural cavernous hemangioma of the cerebellar falx. Preoperative radiosurgery or embolization is recommended for most of the dural cavernous hemangiomas, but surgery for the present dural cavernous hemangioma of the cerebellar falx was performed safely.

Surgical Tips for Medial Sphenoid Wing Meningioma

Medial sphenoid wing meningiomas are more problematic than those meningiomas originating at the pterion. Major arteries and perforators are often involved. An essential principle of surgery is given in this paper. In order to do an operation safely, it is important to define at an early stage of surgery whether the arachnoid membrane separates an artery and a tumor. If one cannot find the separating arachnoid, one should decide to leave the part of tumor attached to the artery. I like to use an intradural resection of the anterior clinoid process after removal of the main tumor mass when the tumor is small. In cases of extensive tumors, extradural bone removal is preferred at the initial stage, so that less brain retraction is needed and the feeding artery is managed. Intradurally, one should detach the tumor initially and then debulk it. Tumor can be separated from the brain surface using the arachnoid plane. One must try to preserve large vessels and perforating branches buried in the tumor to avoid major complications. I recommend dividing the tumor into compartments along a blood vessel, so that one can dissect the vessel from the tumor. Simpson 2 removal is usually tried but I do not hesitate to leave part where no arachnoid membrane is separating major vessels or perforators from the tumor. The video shows where to stop removal. In addition, tumor invading into the cavernous sinus is not removed as long as it does not cause ocular motility disorder.

A novel model of intracranial meningioma in mice using luciferase-expressing meningioma cells

Meningioma research has been hindered by the inability to sequentially measure intracranial tumor growth in a cost-effective, efficient manner. Recently, the luciferase gene has been transfected into cancer lines to obtain cells that express the luciferase enzyme, which oxidizes luciferin in a reaction that releases photon energy that can be measured noninvasively by bioluminescence imaging (BLI) systems. The authors describe a mouse model of intracranial meningioma that uses this novel BLI system. The immortal meningioma cell lines CH-157-MN and IOMM-Lee were transfected with luciferase and neomycin phosphotransferase (LucNeo) and selected with G418. These cells were stereotactically implanted at skull base and cerebral convexity locations in nude mice. Animals were imaged for bioluminescence biweekly, and 5 mice underwent magnetic resonance (MR) imaging. Tumors were harvested for immunohistochemical and ultrastructural analysis. The CH-157-MN-LucNeo and IOMM-Lee-LucNeo cell lines were successfully implanted intracranially in mice. The tumor induction rate for CH-157-MN-LucNeo skull base tumors was 90% (36 of 40 procedures). Statistical analysis of CH-157-MN-LucNeo skull base tumor volume measured on MR imaging correlated with the results of BLI showed an R value of 0.900. The tumors exhibited characteristics of aggressive meningiomas by insinuating along arachnoid planes and invading brain. Noninvasive BLI was successfully used to image intracranial meningiomas in mice. The tumors grew in a fashion similar to that of aggressive meningiomas in humans, and exhibited the microscopic, immunohistochemical, and ultrastructural features characteristic of meningiomas. This animal model overcomes the main obstacle in studying intracranial meningiomas by enabling sequential noninvasive tumor measurement in a cost-effective manner.

The Endoscopic Extended Transsphenoidal Approach for Craniopharyngiomas

The endoscope has recently been applied to the supradiaphragmatic transsphenoidal approach, but only case reports dealing with different pathological features have been described. The authors present their experience with this technique in 10 patients with craniopharyngiomas. A pure endoscopic endonasal technique was used. From November 1998 through May 2005, four males and six females with a craniopharyngioma, either purely supradiaphragmatic (six patients) or with a significant suprasellar component (four patients), were treated. The tumors had a mean diameter of 2.9 cm (range, 1-4 cm); four patients had a major prechiasmatic component and six had a retrochiasmatic one. Seven total, one subtotal, and two partial resections were obtained. Vision symptoms improved significantly in six out of eight patients. Endocrine function did not improve after surgery, and diabetes insipidus was the most frequent deficit, although it was transient in five out of eight patients. Cerebrospinal fluid leak was the most frequent complication and required reoperation in two patients. Postoperative obesity occurred in two patients. No recurrence has yet been documented in the total resection group. The mean follow-up period is 37 months (range, 3-75 mo). The endoscopic technique allows results comparable with the best microscopic series. We think that this technique increases the safety of the procedure because of improved vision. Further studies are required to better define the exact location of the tumor with respect to the arachnoidal plane, the extra-arachnoidal craniopharyngioma being the most suitable for a radical removal using a transsphenoidal supradiaphragmatic approach.

Quantification And Comparison Of Telovelar And Transvermian Approaches To The Fourth Ventricle

To quantify the exposure to the fourth ventricle obtained with the telovelar and transvermian approaches. The telovelar, with and without C1 posterior arch removal, and transvermian approaches were performed on six cadaveric heads. The area of surgical exposure was calculated from triangles formed by defined anatomic points. A robotic microscope was used to determine the "angle of approach" for the same points. The maximal allowable vertical angle of attack to the obex of the fourth ventricle was significantly greater with the telovelar approach than with the transvermian approach (P < 0.002), but there was no difference at the rostral fourth ventricle. The maximal allowable horizontal angle of attack at the level of the obex, Luschka, and rostral fourth ventricle was significantly greater with the telovelar than with the transvermian approach (P < 0.001). Removal of the C1 posterior arch with the telovelar approach significantly increased the vertical angle of approach to the obex (P < 0.001) and rostral aspect of the fourth ventricle (P = 0.005) compared with the telovelar alone. The telovelar approach with C1 arch removal offered a larger working area than the transvermian approach (P < 0.001). Except for the vertical angle to the rostral aspect of the fourth ventricle, the telovelar approach provides greater angle of exposure in all planes than the transvermian approach. Removal of the C1 posterior arch obviates this sole advantage of the transvermian approach. The telovelar approach offers a corridor through noneloquent arachnoid planes and a safe and capacious working environment.

Outcome determinants of pterional surgery for tuberculum sellae meningiomas

Current literature on tuberculum sellae meningiomas is very heterogenous due to wide variation in nomenclature, diagnostic and operative techniques. The aim of this study is specifically to analyze the results of pterional craniotomy for tuberculum sellae meningiomas. A homogenous cohort of 42 consecutively operated tuberculum sellae meningioma cases are reviewed with special emphasis on the effects of pterional microsurgery on visual outcome. This is a retrospective clinical analysis. 42 consecutive patients operated upon during the period of 15 years in a single institution using standard imaging protocols and pterional microsurgery are presented and effect of various variables on visual outcome analysed. 81% of the patients presented with visual symptoms. The mean duration of symptoms was 12 months. Tumour volumes ranged from 7.5 to 210 mm(3). A right sided pterional microsurgery was used in all patients. Complete resection rate was 81%. Vision improved in 58%, worsened in 14%. Non-visual morbidity was 7.1% and mortality was 2.4%. The follow up period of patients ranged from 3 to 192 months (median: 30 months). The mean was 37.5 months (SD = +/-36.7 months) and a recurrence rate of 2.4% was observed. A standard pterional craniotomy using microsurgical technique provides the necessary exposure enabling total removal while keeping the complications to a minimum. Upon analysis of our findings we found that patient age of more than 60, duration of visual symptoms longer than 1 year, severe visual symptomatology, predominantly vertical growth, presence of significant peri-tumoural oedema, absence of an intact arachnoid plane and subtotal removal were correlated with a dismal visual outcome.

Tuberculum sellae meningiomas

Tuberculum sellae meningiomas are a classic tumor of the anterior fossa that present in patients with gradual visual deterioration secondary to optic apparatus compression. If untreated, complete blindness can occur. Treatment involves tumor removal and decompression of the optic chiasm via several operative approaches. Gross-total resection (Simpson Grade I or II) is the goal of treatment and can usually be accomplished safely. Special excision-related considerations include appreciation of arachnoid planes separating the tumor from neural tissue, adequate drilling of osseous elements for optimal exposure, and intraoperative preservation of the vascular supply to the optic apparatus. The authors reviewed their experience at the University of California, San Francisco, in cases of tuberculum sellae meningiomas treated between 1992 and 2002. In most patients, improvement of vision can be achieved with minimal postoperative complications and morbidity.

Expression of IGF-II, IGFBP-2, -5, and -6 in meningiomas with different brain invasiveness.

Meningiomas show clinical characteristics that vary from very benign to clearly malignant with rapid invasive growth and metastases. This study was undertaken to analyze the expression of members in the insulin-like growth factor (IGF) system in meningiomas showing different degrees of brain invasion. Tissue samples from 16 meningiomas were analyzed for members in the IGF family by mRNA in situ hybridization. The meningiomas comprised three groups: I. Benign meningiomas that did not interfere with the arachnoid plane and showed no edema. II. Benign meningiomas that did not respect the arachnoid plane and tumors that caused edema. III. Aggressive and malignant meningiomas that caused edema and showed brain invasion. IGF-II mRNA was identified in all tumors analyzed, and with a clear increase in expression observed in group III tumors. IGFBP-2 mRNA was detected in equal levels in all tumors. IGFBP-5 mRNA levels were highest in the benign group without edema (I) of meningiomas whereas IGFBP-6 mRNA levels were highest in the group with brain invasion (III). Brain invasiveness in degrees from respect of the arachnoid membrane progressing to frank brain invasion correlated with increases in IGF-II and IGFBP-6 expression. High levels of IGFBP-6 may not inhibit IGF-II actions, which is known to be growth promoting in tumors. Instead, IGFBP-6 appears to have an importance for the characteristics of edema and brain invasion in meningiomas.

Expression of matrix metalloproteinases 2 and 9 in meningiomas associated with different degrees of brain invasiveness and edema.

Meningiomas display clinical characteristics that vary from very benign to clearly malignant with rapid invasive growth and metastasis. Benign meningiomas differ in their invasiveness and concomitant edema. This study was undertaken to analyze the expression of matrix metalloproteinases 2 and 9 (MMP-2 and MMP-9, respectively) in meningiomas associated with different degrees of brain invasion and edema. Tissue samples from 16 meningiomas were selected according to tumor invasiveness from a consecutive series of patients. Samples were analyzed for expression of both MMP-2 and MMP-9 by using in situ hybridization. The meningiomas consisted of three types: Group I, benign meningiomas that did not interfere with the arachnoid plane and exhibited no edema; Group II, benign meningiomas that invaded the arachnoid plane and caused edema; and Group III, aggressive and malignant meningiomas that caused edema and displayed brain invasion. In all 16 tumors analyzed, MMP-2 mRNA was identified. Levels of expression of MMP-2 mRNA were similar in all samples, and no correlation with increasing tumor invasiveness or associated edema could be detected. Expression of MMP-9 mRNA was identified in 14 of the 16 tumors, and a clear correlation with increasing tumor invasion into the brain was noted. Meningiomas express both MMP-2 and MMP-9. Tumor invasiveness, which ranged from minor with respect to the arachnoid membrane and progressed to frank brain invasion, correlated with the extent of MMP-9 expression. The findings indicate that MMP-9 expression and brain invasion are relevant mechanisms that must be interfered with in the treatment of aggressive and malignant meningiomas. No such correlation with MMP-2 was found.

Surgical excision of meningiomas involving the clivus: preoperative and intraoperative features as predictors of postoperative functional deterioration.

Neurological deterioration is commonly seen after surgical excision of clival meningiomas; however, an understanding of the risk factors associated with postoperative deterioration can lead to improvements in outcome. In 75 patients with clival meningiomas operated on over a 7-year period, the following data were studied; preoperative variables such as presenting Karnofsky scale score, age, sex, and prior operations or radiation therapy. Radiological findings on magnetic resonance imaging or arteriography, such as the development of the arachnoidal cleavage plane between tumor and the brain stem, brainstem edema, tumor size, extent of compression on the brain stem, vascular encasement, and blood supply from the basilar artery were among other data studied. In addition, intraoperative findings such as development of the arachnoid plane, vascular encasement, and the difficulty of dissection were noted. Finally, each patient's neurological and functional statuses were recorded at 1 week postoperatively and at follow-up examinations. Early postoperative functional deterioration occurred in 45 patients (60%) and ranged from mild (30 patients) to severe (three patients). Significant improvement had occurred by the time of follow-up examination in all but four patients; however, permanent postoperative dysfunction was present in 12 patients. Statistical analysis revealed significant correlations between early functional deterioration and preoperative Karnofsky scale scores, male gender, radiological findings of the absence of an arachnoid plane, edema of the brain stem, and arteriographic supply from the basilar artery. Operative features included difficulty with dissection, an absent arachnoidal cleavage plane, and incomplete tumor resection. Permanent functional deterioration was statistically associated with the following: blood supply from the basilar artery, difficulty of dissection, incomplete tumor resection, and early postoperative dysfunction. Logistical regression analysis revealed that the most important risk factor for early postoperative deterioration was tumor size. Patients with large or giant tumors had a 6.7 to 13 times greater risk of functional deterioration, respectively, than patients with small- or medium-sized tumors. Excluding tumor size, the most important factor for permanent deterioration was blood supply from the basilar artery. Patients in this category had a 4.4 times greater risk of permanent functional deterioration. Three stages of tumor relationship to the brainstem arachnoid and pial membranes are proposed. Based on the results of this clinical study of clival meningiomas, suggestions are made for changes in the management strategy of these difficult lesions.

Role of pia mater vascularization of the tumour in the surgical outcome of intracranial meningiomas.

The authors reviewed a personal series of 150 consecutive cases of intracranial meningiomas operated on between 1974 and 1988 with the aim of finding out the main prognostic factors determining surgical outcome. Severity of pre-operative clinical status and size of the tumour were found to be significant adverse factors, p < 0.001 and p < 0.01, respectively. In this article the authors stress on the role played in prognosis by pia mater vascularization of the tumour. When the tumour vascular supply predominated from pial-cortical arteries, in most cases cleavage could not be found in the arachnoid plane, but only in the subpial plane (because of incorporation of pia mater into the tumour "capsule"). Clinical consequences were that in the most eloquent areas (for example in the central region) a bad outcome--with transient or permanent deficit--frequently occurred when cleaving could not be performed in the arachnoid plane (p < 0.001). The neurological disorders were due to cortical and underlying sub-cortical ischaemia and haemorrhagic infarction. Participation of the pia mater in the tumour vascular supply can be predicted pre-operatively, directly on selective internal/external carotid angiograms, indirectly by the presence of an important peritumoural hypodensity on CT scan (which--according to our findings--is an indication of predominant pial-cortical vascular supply to the tumour). The positive correlation between cortical-pial supply (and its consequences) and tumour size (p < 0.001), pleads for surgery of meningioma at the earliest possible stage provided there are no contra-indications.