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Table of Contents    
Year : 2018  |  Volume : 66  |  Issue : 4  |  Page : 1081-1086

Olfactory groove meningiomas: An analysis based on surgical experience with 129 cases

1 Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel; Department of Neurosurgery, Lilavati Hospital and Research Centre, Bandra (E), Mumbai, Maharashtra, India
2 Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, India

Date of Web Publication18-Jul-2018

Correspondence Address:
Dr. Atul Goel
Department of Neurosurgery, K.E.M. Hospital and Seth G.S. Medical College, Parel, Mumbai - 400 012, Maharashtra
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Source of Support: None, Conflict of Interest: None

DOI: 10.4103/0028-3886.236989

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 » Abstract 

Objective: The surgical strategy and outcome for 129 patients operated for an olfactory groove meningioma is retrospectively analyzed.
Material and Methods: One hundred and twenty nine patients with an olfactory groove meningioma operated between the years 1987 and 2016 were analyzed on the basis of clinical and radiological factors that appeared to affect the conduct of surgery and its outcome. Each factor was given points, and the points were added to obtain a score. On the basis of the score, the tumors were divided into three grades. The grades determined the difficulties that could be anticipated during surgery. In the initial part of the series, a bifrontal craniotomy was done to resect the tumor in all patients. In the later half of the series, majority of the patients were operated by the use of a unifrontal craniotomy. The aim of surgery was to resect the tumor completely.
Results: Total tumor resection was achieved in 86 patients, and subtotal tumor resection with less than 10% tumor left behind was achieved in 43 patients. Seven patients died in the immediate postoperative period. All patients where a subtotal tumor resection was done and where the patient died after surgery had a higher grade tumor. The average follow-up period was 82 months. There was non-symptomatic recurrence in 11 patients.
Conclusions: The location and size of the tumor, extent and duration of visual symptoms, extent of tumor adjoining cerebral edema, encasement of anterior cerebral artery complex and extension in the extracranial compartment were more important factors that affected the outcome of surgery.

Keywords: Anterior cerebral artery, olfactory groove meningioma, optic nerves
Key Message: This study assessed in patients undergoing surgical excision of olfactory groove meningiomas, the factors that determined the difficulties encountered during surgery, assisted in predicting the extent of resectability, and helped in prognosticating the surgical outcome. A grading score has been proposed that can characterize the nature of the tumor and helps in streamlining the preoperative evaluation as well as in predicting the course of surgery and its outcome.

How to cite this article:
Goel A, Bhaganagare A, Shah A, Kaswa A, Rai S, Dharurkar P, Gore S. Olfactory groove meningiomas: An analysis based on surgical experience with 129 cases. Neurol India 2018;66:1081-6

How to cite this URL:
Goel A, Bhaganagare A, Shah A, Kaswa A, Rai S, Dharurkar P, Gore S. Olfactory groove meningiomas: An analysis based on surgical experience with 129 cases. Neurol India [serial online] 2018 [cited 2020 Jan 18];66:1081-6. Available from:

Surgery for an olfactory groove meningioma forms an integral part in the curriculum of a neurosurgeon. Despite their imposing presence and profile, surgical excision of these tumors is a relatively safe surgical procedure. Various reports suggest that an increasing experience in the field of neurosurgery improves the surgical outcome.[1],[2],[3] We retrospectively analyzed our experience in treating 129 cases of olfactory groove meningiomas. The analysis is based on factors that probably determined the difficulties that were encountered during surgery, assisted in predicting the extent of resectability, and helped in prognosticating the surgical outcome.

 » Material and Methods Top

One hundred and twenty nine patients with an olfactory groove meningioma (79 women and 50 men) were treated in the neurosurgery department of the authors between 1987 and 2016 [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]. The ages of the patients ranged from 18–75 years (the mean age being 46 years). The principal symptoms and signs at presentation are indicated in [Table 1]. The clinical and radiological characteristics of the tumor are summarized in [Table 2]. Points were given to each relevant presenting sign and symptom and to radiological features. These points were assigned according to their possible significance in affecting the conduct of the surgical procedure. Severe visual deficit (SVD) was classified as a vision less than the ability to count fingers at a distance of six meters. Partial/mild visual deficit (PVD) was classified when there was visual blurring or a visual field deficit. Headache and vomiting, as symptoms, were frequent, but these factors were not included for grading the tumors. Intellectual decline, memory and behavioral alterations and urinary incontinence were observed in atleast 53 cases. Loss of smell was a uniform symptom. This symptom was not assigned any score, as it was not appropriately or completely analysed both before and after surgery. Moreover, it was unclear if the extent of affection of sense of smell influenced the conduct of surgery or its outcome. [Table 3] shows the tumor grade that was determined by the sum of total points of each clinical and radiological parameter.
Figure 1: Images of a 42-year old female patient. (a) T1 weighted sagittal contrast scan showing the large olfactory groove meningioma. (b) T1 weighted axial image showing the tumor and the displaced anterior cerebral arteries. (c) Post-operative coronal contrast image of the MRI showing excision of the tumor. (d) Post-operative sagittal contrast image showing excision of the tumor

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Figure 2: Images of a 75-year old male patient. (a) T1 weighted sagittal contrast scan showing the homogenously enhancing olfactory groove meningioma. (b) Coronal contrast enhanced image showing the olfactory groove meningioma having an eccentric extension. Extension of the tumor in the paranasal sinuses is seen. (c) T2 weighted axial image showing the tumor and the displaced anterior cerebral vessels. (d) Post-operative contrast image showing excision of the tumor

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Figure 3: Images of a 31-year old male patient. (a) Axial CT image showing an olfactory groove meningioma. (b) Coronal image showing the tumor. (c) Post-operative image 14 years after surgery showing no evidence of the tumor. (d) Post-operative image 17 years after surgery showing a relatively small recurrence

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Figure 4: Images of a 50-year old female patient. (a) Axial image of CT scan showing the calcified olfactory groove meningioma. (b) Axial image of MRI showing the partly isointense and partly hypointense (calcified) tumor. (c) Sagittal MRI scan showing the large olfactory groove meningioma occupying the anterior, middle and posterior thirds of the anterior cranial fossa

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Figure 5: Images of a 40-year old female patient. (a) Contrast enhanced sagittal image showing the huge tumor. (b) Contrast enhanced coronal image showing the relation of the tumor to the anterior cerebral and internal carotid arteries. (c) Axial image showing the tumor and enostosis of the anterior cranial fossa floor. (d) T2 weighted coronal scan showing the tumor having paranasal sinus extension and severe tumor surrounding edema

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Table 1: Table showing symptoms of the patients at the time of presentation

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Table 2: Table showing the clinical and radiological features that were used for grading the tumors

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Table 3: Table showing the grading of olfactory groove meningiomas

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Radiological investigations included either or both computed tomography (CT) scan and magnetic resonance imaging (MRI). CT angiography was done in 10 patients. Digital subtraction angiography was performed in 5 cases, earlier on in experience. The embolization of the tumor blood vessels was not performed.

 » Results Top

Bifrontal craniotomy was performed in 41 and unifrontal craniotomy was performed in 88 patients. Out of the 44 cases operated after 2006, a bifrontal craniotomy was performed in 10 patients and an unifrontal craniotomy was performed in 34 patients. The indication for an unifrontal craniotomy was when the tumor was essentially eccentric in placement and the extension on the contralateral side was approximately less than one-third of the total tumor volume. After 2014, all cases were operated using an unifrontal exposure. The surgical landmarks of an unifrontal craniotomy as used by us were similar to that reported by Samii et al.[1] A subfrontal approach was adopted to expose and resect the tumor. Whenever necessary, a part of the frontal brain just anterior to the tumor was resected to expose the anterior dome of the tumor. The tumor was then dissected off the basal attachment. Space for basal dissection and coagulation was obtained by a simultaneous tumor debulking. The tumor tissue extending into the paranasal sinuses was resected by the same surgical exposure. All attempts were made to preserve the olfactory nerves atleast on one side. Our technique involved a relatively quick intra-tumoral debulking and the minimal use of cautery during the entire operation. By using standard microneurosurgical techniques, tumor resection was done in a piece-meal fashion. The location of the nodal point of attachment of the tumor, in the anterior third, middle third or the posterior third of the olfactory groove had an impact on the extent of surgical difficulties that were encountered during surgery. The outcome of the entire surgical procedure depended on the preservation of anterior cerebral artery and its branches and the internal carotid artery. Radical removal of the tumors was attempted, but if the dissection of the tumor from the anterior cerebral artery and the internal carotid artery and its branches carried a risk of damage to these vessels, the dissection was discontinued and that portion of the tumor was left behind. The basal dural attachment of the tumor was widely coagulated. No special attempt was made to remove the dura or the involved bone. By adopting standard techniques, the exposed frontal air sinus was sealed.

The follow-up ranged from 6 months to 29 years (mean 82 months). Seven patients died in the immediate postoperative period. All these patients had a grade 3 tumor. The cause of death was hemorrhage into the site of the operative field in 3 cases, and infarct in the territory of anterior cerebral artery. Hundred and ten patients have returned to normal life. No patient was dependent for activities of daily living. All patients who had higher mental function affection before surgery, improved in their symptoms following surgery. The patients improved in their memory disturbances, in their ability to concentrate and in their altered behaviour and were appropriately able to interact socially.

During the period of follow-up, there has been relatively small and clinically asymptomatic recurrence in 11 cases. However, no surgical rexploration or treatment with radiation therapy was done in any of these cases.

 » Discussion Top

Olfactory groove meningiomas are relatively common intracranial lesions. The literature review suggests that they represent approximately 4.5 – 18% percent of intracranial meningiomas.[4]

Various authors have analyzed this subject for more than a century.[1],[2],[3],[4],[5],[6],[7],[8],[9],[10],[11],[12] These tumors arise from the floor of the anterior cranial fossa over the cribriform plate of the ethmoid bone. The site of origin frequently extends anteriorly or posteriorly and across the midline from this primary site. Although several speculations have been put forth, the exact reason as to why this site is more prone for occurrence of meningiomas is unclear. Due to their slow rate of growth, and their site and location in vicinity of the frontal lobes, these tumors achieve a significantly large size at the time of diagnosis and have relatively innocuous presenting clinical signs. A large tumor size, a firm and vascular nature, extension on both sides of the midline and a wide basal attachment are the general characteristics.

Considering the relative safety and ease involved in their resection, and the provision of an opportunity to learn the art of tumor debulking and of achieving hemostasis, these tumors form a resource material for learning the subject of neurosurgery. All of the facets involved in the conduct of neurosurgery are tested elaborately during their excision. On the other hand, surgical failures can lead to a devastating clinical outcome.

Although a significant majority of resections of olfactory groove meningiomas are safe surgical operations, there are several tumor and patient related factors that may influence the conduct the surgery. We attempt to classify these tumors to assess the extent of difficulties that may be encountered during surgery, the postoperative result and the long-term outcome. Points were assigned to each individual factor. These points were given relative to the other parameters in the same group as well as to parameters in other groups. The final grading of the tumor was based on the score, which was a sum total of the points.

A preponderance of olfactory groove meningiomas in female patients has been frequently observed. There were 79 female patients in the present series. Most tumors were encountered in patients in the third to fourth decade of life. Younger patients tolerated surgery better than older patients. Systemic factors, such as hypertension and diabetes mellitus, could affect the surgical procedure and outcome to a certain degree.

Majority of the patients presented with symptoms of headache (115 patients - 89%). As these meningiomas generally arise from one side of the midline, affection of the sense of olfaction can be an early symptom. It is, however, seldom a dominant presenting symptom. Large tumor dimension and displacement of brain is generally presumed to have an impact on higher mental function. In the series, 53 patients had atleast some degree of intellectual decline, abnormal behavior or affected memory function. Focal or generalized convulsions as presenting symptoms were identified in 54 cases. An altered level of consciousness, that often persists after an episode of generalized convulsion, was observed in 7 patients at the time of admission.

The extent of visual deficit was an important factor that determined the course and outcome of surgery. The more extensive the involvement of the optic nerve, as depicted by the extent of visual deficit, the more intense was the relationship of the tumor with the optic nerve and the internal carotid artery and its branches to the tumor, and consequently, the more difficult was the dissection. Optic canal intrusion is not common in tumors in this location and was not seen in any patient in our study. Visual affection secondary to longstanding papilledema has been identified for a long time. The duration of visual deficits also suggested the rate of growth of the tumors. Longer the presence of tumor in the brain, more intimate were its relationship with the adjoining neural and vascular structures.

A large tumor size is the hallmark of these tumors. The tumors grow progressively in size, make space for their growth, displace the adjoining brain, and yet, present with relatively subtle symptoms. The tumor size has been associated with difficulty in tumor resection and has been identified to have an impact on the overall surgical conduct and its postoperative and long-term outcome.[13] The primary or centre-point of tumor location in the region of anterior, middle or posterior olfactory groove, influenced to an extent the surgical conduct. It was observed that the tumors encountered during pregnancy were more vascular and there was more extensive cerebral edema; both of these factors resulted in difficulties during surgery.[14]

Hemispheric deficits, seizures, altered behavior, and altered sensorium were rare manifestations despite the large tumor sizes encountered. These clinical features indicate the nature of association of the tumor with the parenchyma and the possible surgical issues.

An idea of the extent of firmness of the tumor could be achieved by an analysis of signal intensities on CT scan and MRI.[13],[14],[15],[16],[17] The presence of calcification on preoperative imaging was indicative of the firm nature of the tumor. The presence of enostosis and hyperostosis was seen in the firmer varieties of tumor. The presence and extent of cerebral edema on imaging was indicative of the rate of growth of the tumor, reaction from the brain and the intimacy of brain-tumor interface. The nature of cerebral edema also indicated the brain reaction after the craniotomy, the need for cortical resection to expose the tumor, and the difficulties encountered during the conduct of the surgical procedure.

A number of surgical approaches have been discussed for olfactory groove meningiomas.[1],[2],[3],[4],[10],[18],[19] A bicoronal scalp incision and bifrontal craniotomy has been the standard and conventional surgical approach. Some authors have identified the pterional surgical exposure as a safer and better surgical option.[4],[11] Whilst a majority of the tumors in the presented series were resected using a conventional bifrontal craniotomy, in the later part of the series, a unifrontal exposure was preferentially adopted. The degree of surgical exposure in each patient did not correlate with the grading system described. More experience with tumor surgery and familiarity with the nature of these tumors influenced the use of a smaller exposure. However, despite our experience and comfort level with a unifrontal surgical approach, the frequently encountered huge tumor size with a wide basal attachment forced the adoption of the bifrontal surgical approach in higher-grade tumors. In small to moderate sized tumors, retraction of the frontal brain off the orbital roof has to be necessarily done gently avoiding its injury. However, in larger tumors, basal frontal and frontal polar brain resection anterior to the tumor can provide an effective, wide, safe and quick exposure. Brain resection has to be necessarily limited and can be done after elevating the frontal brain. Frontal brain resection to enhance surgical exposure of the tumor was initially proposed by both Cushing and Dandy in 1938.[6] However, only a few subsequent and modern articles discuss the validity and use of frontal brain resection in exposure of the anterior face of the tumor. The extent of surgical exposure in each patient did not correlate with the grading system described. Well-described surgical steps like ligation and cutting of the superior sagittal sinus and an interhemispheric access to the tumor were not adopted in any case. Skull base approaches that involve removal of the orbital rim or zygomatic bone or its processes were not adopted. A large number of tumors were relatively well circumscribed and had a clear plane of dissection from the adjoining brain and blood vessels and were relatively easy to dissect and excise. The major surgical issue in the series was the relationship of the tumor with the anterior cerebral artery complex and the optic nerves. Despite the encasement of the internal carotid artery as seen on MRI, it was observed that the tumor lobulations surrounded the internal carotid artery and the dissection was relatively simple. All our patients who died experienced an intraoperative damage to the anterior cerebral artery or its major branch during surgery.

Our surgical policy was to coagulate the dural site of tumor attachment. Whilst the philosophy of surgery was to maximize tumor resection, no attempts were made to resect the involved dura. No bone removal was done, unless the part of enostosis or bone projection interfered with the surgical process of tumor resection. In cases where there was extension of the tumor on both sides of the anterior cranial fossa basal dura, the extracranial component of the tumor and the involved dura were resected utilizing the same exposure. The reconstruction of the skull base was done in such cases using a vascularized pedicled pericranial graft.[20],[21] In all other cases, there was no need for basal dural reconstruction. Literature indicates a large variation in the policy regarding the need for resection of the involved dura and the basal bone. Although several authors identify the association of rate of tumor recurrence with the extent of tumor resection, our belief is that it is tumor biology and tumor growth characteristics that determine recurrence. The grading scale assisted in characterization of the aggression of the tumor, and to an extent, in prognosticating the potential of recurrence. The surgical outcome was satisfactory in 122 cases. There was recovery of vision to a varying extent in 50 cases. No patient worsened in vision following the operation. Recovery in higher function was seen in all the patients who had this affliction before surgery. Although advocated by some, no postoperative irradiation was done, even when a portion of the tumor was left behind. Radiation treatment was given in 9 cases where the tumor was aggressive in nature and histological examination suggested an 'atypical' character of the tumor. Two patients having an en-plaque meningioma were subjected to radiation treatment.

 » Conclusions Top

The proposed grading score can characterize the nature of the tumor. The scores help in streamlining the preoperative evaluation and in predicting the course of surgery and its outcome.

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Conflicts of interest

There are no conflicts of interest.

 » References Top

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Nanda A, Maiti T, Bir S, Konar S, Guthikonda B. Olfactory groove meningiomas: Comparison of extent of frontal lobe changes after lateral and bifrontal approaches. World Neurosurg 2016;94:211-21.  Back to cited text no. 2
De Aguir P, Tahara A, Almeida A, Simm R, da silva A, Maldaun V. Olfactory groove meningiomas: Approaches and complications. J Clin Neurosci 2009;16:1168-73.  Back to cited text no. 3
Hassler W, Zentner J. Pterional approach will be surgical treatment of olfactory groove meningiomas. Neurosurgery 1989;25:942-7.  Back to cited text no. 4
Downes A, Freeman J, Ormond D, Lillihei K, Youssef A. Unilateral tailored fronto-orbital approach for giant olfactory groove meningiomas: Technical nuances. World Neurosurg 2015;84:1166-73.  Back to cited text no. 5
Cushing H, Eisenhardt L. The olfactory meningiomas with primary anosmia. In Cushing H, Eisenhardt L (eds) Meningioma, Springfield: Charles and Thomas 1938:250-82.  Back to cited text no. 6
Ojemann RG: Olfactory groove meningioma. In: Al Mefty O (ed): Meningiomas, New York, Raven Press, 1991, P 383-93.  Back to cited text no. 7
Hentshel SJ, DeMonte F. Olfactory groove meningioma: Surgical techniques and pitfalls. Surg Neurol 2000;54:415-17.  Back to cited text no. 8
Obeid, Fayez MD. Al-Mefty, Ossama M D. Recurrence of olfactory groove meningiomas. Neurosurgery 2003;53:534-43.  Back to cited text no. 9
Mayfrank L, Gilsbach JM. Interhemispheric approach for microsurgical removal of olfactory groove meningiomas. Br J Neurosurg 1996;10:541-5.  Back to cited text no. 10
Turazzi S, Cristofori L, Gambin R, Bricolo A. The pterional approach for the microsurgical removal of olfactory groove meningiomas. Neurosurgery 1999;45:821-5.  Back to cited text no. 11
Bassiouni H, Asgari S, Stolke D. Olfactory groove meningiomas: Functional outcome in a series treated microsurgically. Acta Neurochir (Wein) 2007;149:109-21.  Back to cited text no. 12
Goel A, Gupta S, Desai K. New grading system to predict resectability of anterior clinoid meningiomas. Neurol Med Chir 2000;40:610-6.  Back to cited text no. 13
Goel A, Muzumdar D, Desai KI. Tuberculum sellae meningiomas: A report on management on the basis of a surgical experience with 70 patients. Neurosurgery 2002;51:1358-63.  Back to cited text no. 14
Goel A, Kothari M. Cavernous sinus meningiomas. J Neurosurg 2010;113:1085.  Back to cited text no. 15
Goel A, Muzumdar DP, Nitta J. Surgery on lesions involving cavernous sinus. J Clin Neurosci 2001;8 Suppl 1:71-7.  Back to cited text no. 16
Goel A, Kothari M. Meningiomas: Are they curable? J Craniovertebr Junction Spine 2016;7:133-4.  Back to cited text no. 17
De Almeida J, Carvalho F, Filho F, Kiehl TR, Koutourousiou M, Su S. Comparison of endoscopic endonasal and bifrontal craniotomy approaches for olfactory groove meningiomas: A matched pair analysis of outcomes and frontal lobe changes on MRI. J Clin Neurosci 2015;22:1733-41.  Back to cited text no. 18
Koutourousiou M, Fernandez-Miranda J, Wang E, Snyderman C, Gardner P. Endoscopic endonasal surgery for olfactory groove meningiomas: outcomes and limitations in 50 patients. Neurosurg Focus 2014;37:E8.  Back to cited text no. 19
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  [Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]

  [Table 1], [Table 2], [Table 3]


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