olfactory groove meningiomas: functional outcome in a series treated microsurgically

Acta Neurochir (Wien) (2007) 149: 109–121

DOI 10.1007/s00701-006-1075-z

Printed in The Netherlands

Clinical ArticleOlfactory groove meningiomas: functional outcome in a series treatedmicrosurgically

H. Bassiouni, S. Asgari, and D. Stolke

Department of Neurosurgery, University Hospital Essen, Essen, Germany

Received January 10, 2005; accepted November 23, 2005; published online December 21, 2006

# Springer-Verlag 2006

Summary

Background. A systematic investigation of long-term

follow-up results after microsurgical treatment of pa-

tients harbouring an olfactory groove meningioma, par-

ticularly with regard to postoperative olfactory and

mental function, has rarely been performed. We reas-

sessed a series of patients treated microsurgically for an

olfactory groove meningioma in regard to clinical pre-

sentation, surgical approaches and long-term functional

outcome.

Method. Clinical, radiological and surgical data in a

consecutive series of 56 patients suffering from olfactory

groove meningioma were retrospectively reviewed.

Findings. Presenting symptoms of the 41 women and

15 men (mean age 51 years) were mental changes in

39.3%, visual impairment in 16.1% and anosmia in

14.3% of the patients. Preoperative neurological exam-

ination revealed deficits in olfaction in 71.7%, mental

disturbances in 55.4% and reduced vision in 21.4%

of the cases. The tumour was resected via a bifrontal

craniotomy in 36, a pterional route in 13, a unilateral

frontal approach in 4 and via a supraorbital approach

in 3 patients. Extent of tumour resection according to

Simpson’s classification system was grade I in 42.9%

and grade II in 57.1% of the cases. After a mean follow-

up period of 5.6 years (range 1–13 years) by clinical

examination and magnetic resonance imaging (MRI),

86.8% of the patients resumed normal life activity.

Olfaction was preserved in 24.4% of patients in whom

pre- and postoperative data were available. Mental and

visual disturbances improved in 88 and 83.3% of cases,

respectively. Five recurrences (8.9%) were observed and

had to be reoperated.

Conclusions. Frontal approaches allowed better re-

section of tumours with gross infiltration of the anterior

cranial base, tumours extending into the ethmoids or

nasal cavity and in cases with deep olfactory grooves.

Preservation of olfaction should be attempted in patients

with normal or reduced smelling preoperatively.

Keywords: Meningioma; olfaction; olfactory groove;

recurrence; skull base; surgical approach.

Introduction

Meningiomas of the midline anterior skull base in-

clude tumours originating from the dura of the cribriform

plate, planum sphenoidale and tuberculum sellae and

account for about 10% of all intracranial meningiomas

[41]. For clinical, radiological and surgical purposes true

olfactory groove meningiomas, i.e. tumours originating

from the dura between the crista galli and the fronto-

sphenoid suture should be differentiated from planum

sphenoidale and tuberculum sellae meningiomas [8, 32].

Tumours arising from the latter sites usually come to

clinical attention at an early stage with visual deteriora-

tion, while this is a late feature in olfactory groove menin-

giomas which usually remain clinically quiescent during

the early phase of growth. Anatomically, olfactory groove

meningiomas arise from the weakest part of the skull

base, the cribriform plate, which makes them prone to

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Olfactory groove meningiomas 111

infiltrate the underlying bone and extend into the para-

nasal sinuses and nasal cavity. This is a rare feature in

planum sphenoidale or tuberculum sellae meningiomas.

A systematic assessment of functional outcome after

resection of olfactory groove meningiomas, particularly

in respect to olfactory function, has rarely been performed

[3, 30, 46]. We retrospectively analysed meningiomas

with a predominant origin from the dura of the cribriform

plate with regard to clinical presentation, different surgi-

cal approaches and follow-up results which were treated

microsurgically in our institution.

Patients and methods

Patient population

From June 1990 till June 2003, an olfactory groove

meningioma was microsurgically resected in 56 conse-

cutive patients in our department. The medical charts,

surgical records and radiological studies were retrospec-

tively reviewed in these patients. Only tumours with a

primary origin from the dura of the cribriform plate were

included in this report. Lesions with a predominant dural

origin from the planum sphenoidale, tuberculum sellae,

anterior clinoidal process or orbital roof were not con-

sidered in this series.

Radiological studies

Magnetic resonance imaging (MRI) was obtained pre-

operatively in all patients and clearly demonstrated the

relationship of the tumour with the optic nerves, chiasm

and the anterior cerebral arteries (ACA) (Fig. 1a, b).

These vessels were encased by the tumour in three pa-

tients. A significant bifrontal or unilateral edema was

displayed on MRI in 34 patients. CT with bone algo-

rithms, performed preoperatively in 23 patients revealed

a hyperostosis of the crista galli or the cribriform plate

in six and erosion of the cribriform plate in four cases

(Fig. 2c). Cerebral angiography was performed regularly

early in the study period to demonstrate tumour vascu-

larity, provide information regarding ACA displacement

and to evaluate the possibility of preoperative embolisa-

tion. In all 23 cases studied angiographically, the tumour

was predominantly supplied by the anterior or posterior

ethmoidal branches of the ophthalmic artery and preo-

perative partial embolisation was performed in two pa-

tients with occlusion of the anterior branch of the middle

meningeal artery (Fig. 2f). Angiography is no longer

performed in these tumours in our institution. Mean

maximal diameter of the tumours as depicted from pre-

operative MRI was 5.2 cm (range: 2.5–7.5 cm).

Tumour extension and dural attachment

As shown by preoperative MRI and confirmed intrao-

peratively, the tumour was attached to the cribriform

plate, adjoining part of the planum sphenoidale, crista

galli and medial orbital roofs on both sides in 24 patients.

Tumours in these cases were broad-based, were larger

than 5.5 cm in maximal diameter and had an almost

symmetric growth on both sides. The tumour attachment

area was restricted to the cribriform plate and adjacent

part of the orbital roofs on both sides in 19 patients.

A pure unilateral dural origin from the cribriform plate

and adjoining anterior cranial base was observed in 13

patients, on the left side in six and on the right side in

seven cases (Fig. 3).

Bilateral extension of the tumour into the ethmoidal

cells was disclosed on preoperative coronal MRI in two

cases and unilateral extension in one. The tumour reached

the nasal cavity in two additional cases (Fig. 4a, b). The

meningioma extended into the optic canal on one or both

sides in five patients, all of whom had visual distur-

bances preoperatively.

Surgical approaches

Thirty-six patients with a bilateral tumour were oper-

ated via a bifrontal craniotomy with opening of the fron-

tal sinus, double ligation and division of the anterior end

of the superior sagittal sinus with subsequent subfrontal

Fig. 3. Artist’s sketch showing dural attachment of olfactory groove

meningiomas. (A) Bilateral attachment to the cribriform plate, planum

sphenoidale and orbital roofs (24 cases), (B) tumours attached to the

cribriform plate and medial orbital roofs bilaterally (19 cases),

(C) Unilateral attachment to the cribriform plate and medial orbital

roof (13 cases). Posterior extension over the tuberculum sellae (straight

arrow) was observed in four, encroachment into the optic canal (curved

arrow) in five cases


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removal of the meningioma. This approach has been

described in detail [27, 28, 36]. Additionally, a bilateral

tumour was extirpated via a pterional approach in seven

patients. The contralateral tumour part was removed

after partial resection of the falx cerebri and crista galli

[15, 47]. Tumours restricted to one side were resected

through a unilateral frontal approach in four cases, via

a pterional approach in six and a lateral supraorbital

(‘key-hole’) craniotomy in three patients [35]. The latter

approach was used in small tumours up to 3.5 cm in

diameter and was endoscopically-assisted in one case

with a deep olfactory groove. In all but three patients

were the tumour had been removed via a frontal craniot-

omy the floor of the anterior cranial base was covered

with a vascularized galea-periosteal flap reinforced with

sutures and fibrin glue. A hyperostosis of the crista galli

and=or cribriform plate was removed by drilling in

16 patients. Tumours that had invaded into the ethmoi-

dals or nasal cavity were removed via a bifrontal cra-

niotomy. This was combined with a lateral rhinotomy

performed by members of the otolaryngology depart-

ment in two cases.

Patient’s follow-up

All patients were followed-up with clinical examina-

tion and MRI studies six months and one year after

surgery. Thereafter, patients were re-examined at one

or two year intervals based on each follow-up result.

Postoperative assessment of mental function was avail-

able in 25 of 31 patients with preoperative personality

changes. Olfactory function was tested semi-quantita-

tively before surgery and on each follow-up examina-

tion with different odours for each nostril separately.

Preoperatively, test results were reliably obtained in

46 patients. In the remainder mental changes allowed

only a gross differentiation between smelling and not

smelling at best. Postoperative results of olfactory tests

were available for analysis in 41 patients. All patients

with visual disturbances had detailed pre- and post-

operative ophthalmological investigations, including

visual acuity, visual fields, fundoscopy and intraocular

pressure measurement.

Results

Clinical data

The 41 women and 15 men had a mean age of

51 years (range 30–74 years). The most common presen-

ting symptoms were mental disturbances in 22 patients

(39.3%), headache in 11 (19.6%), visual deterioration in

nine (16.1%) and anosmia in eight cases (14.3%). The

duration of symptoms was longest for mental changes

(mean 3.2 years, range 3 months to 12 years), medium in

duration for anosmia and headache (mean 10 months,

range 4–18 months and mean 8.3 months, range 3 weeks

to 2 years, respectively) and shortest for visual distur-

bances and seizures (mean 2 months, range 1 week and

6 months and 3 weeks, range 1–7 weeks, respectively).

The neurological examination revealed, in order of fre-

quency, disturbance of olfaction in 33 of 46 patients

(71.7%) that could be reliably tested, personality changes

in 31 (55.4%), and decreased vision in 12 patients

(21.4%) (Table 1).

Surgical aspects

The meningioma was completely resected in all pa-

tients irrespective of the surgical approach applied. A

Simpson [39] grade I resection was achieved in 24 pa-

tients, 23 had been operated through a frontal craniotomy

and one via a pterional approach. This group included all

patients with tumour invasion into the ethmoids and nasal

cavities. The dural attachment area of the tumour was

coagulated in 32 patients (Simpson grade II removal).

In five cases where the tumour had encroached into the

optic canal these tumour extensions could simply be

pulled out in two but necessitated opening of the optic

canal in three patients. The optic nerves and chiasm were

posteriorly and inferiorly dislocated by the tumour in 20

cases. A nodular posterior growth of the tumour pushing

Table 1. Preoperative symptoms and neurological signs in patients with

olfactory groove meningioma

Symptom No. of patients Patients (%)

Mental changes 22 39.3

Headache 11 19.6

Visual disturbance 9 16.1

Disturbance of olfaction 8 14.3

Dizziness 6� 10.7�Seizures 5 8.9

Hemiparesis 1 1.8

Neurological signs

Disturbance of olfaction 33 71.7��– Anosmia 20 43.5��– Hyposmia 13 28.3��Mental disturbance 31 55.4

Decreased vision 12 21.4

Papilledema 3 5.4

Hemiparesis 1 1.8

Incidental finding 1 1.8

� Symptom ameliorated in all patients postoperatively.�� Percentage out of 46 patients that could be tested preoperatively.


both optic nerves laterally was removed in three patients.

In all cases with intimate relationship of the meningioma

to the optic nerve, chiasm or ACA there was a clear sep-

arating arachnoid membrane facilitating tumour removal

from these structures.

Intraoperative data regarding preservation of the ol-

factory nerves were available in 40 patients. The nerves

were grossly distorted or infiltrated by the tumour in 26

patients. However, the nerves were protected by an ara-

chnoid sheath bilateral in 5 and unilateral in 9 cases. At

the end of the surgical procedure the nerve was in ana-

tomic continuity in 12 patients on one side and in four

cases bilaterally.

In patients with gross tumour extension into the eth-

moids and nasal cavities, the skull base defect was sub-

sequently covered with a titanium mesh and periosteal

flap in two cases and with a double layer of galea-periost

in three patients.

Postoperative olfactory function

All patients with preoperative anosmia remained

anosmic although one olfactory tract could anatomically

be preserved in three patients and both tracts in one case.

Olfaction was preserved on one side in three patients

who were hyposmic before surgery and who were trea-

ted via a unilateral approach for a unilateral menin-

gioma. A normal sense of smelling was maintained in

five cases with normal olfaction preoperatively (three

operated via a bifrontal and two via a pterional route).

A postoperative deterioration of olfaction was found in

15 patients. Two patients with a normal preoperative

sense of smell were rendered hyposmic and six anosmic.

Seven patients who could smell on one nostril preopera-

tively became anosmic. Loss of olfaction was usually

noted immediately after surgery. However, one patient

became anosmic three months after surgery and later

suffered from cacosmia. Three patients with reduced ol-

faction before surgery reported an amelioration in smel-

ling postoperatively. Two of these patients had preserved

olfaction on one side. The third in whom both olfactory

tracts could not be preserved intraoperatively was actu-

ally anosmic on testing (Table 2).

Mental disturbances

Thirty-one patients (55.4%) had mental and personal-

ity disturbances preoperatively. In order of frequency,

short-memory deficits were present in all, inability to

concentrate in 25, lethargy and apathy in five, confusion

in four and dementia in three patients. An uninhibited

frontal behaviour (‘Witzelsucht’) was observed in two

cases. Four patients had a characteristic evolution with

aggressiveness and irascibility in the early stages of dis-

Table 2. Postoperative follow-up results in patients with olfactory groove meningioma

Symptom No. of patients (%) Functional outcome (%)

Preoperative Postoperative

Olfaction�Normal 13 (31.7%) 5 (12.2%) preserved: 10 (24.4%)

Hyposmia 11 (26.8%) 5 (12.2%) deterioration: 15 (36.6%)

Anosmia 17 (41.4%) 29 (70.7%) amelioration: 2 (4.9%)

Cacosmia 0 1 (2.4%)��

Mental function��Normal function 0 19 (76%) amelioration: 22 (88%)

Short memory deficit 21 (100%) 3 (14.3%) deterioration: 2 (8%)

Attention deficit 18 (85.7%) 3 (14.3%) no change: 1 (4%)

Apathy 5 (23.8%) 2 (9.5%)��Desorientation 4 (19.0%) 0

Uninhibited behaviour 2 (9.5%) 0

(‘Witzelsucht’)

Dementia 1 (4.8%) 1 (4.8%)

Visual function

Decreased visual acuity 12 (21.4%) 4 (7.1%)�� amelioration: 10 (83.3%)

deterioration: 2 (16.7%)��Visual field defect 4 (7.1%) 1 (1.8%) amelioration: 4 (100%)

deterioration: 0

� 41 patients with pre-and postoperative olfactory testing, �� patient anosmic on testing, �� postoperative results in 25 out of 31 patients with

mental disturbances evaluated pre-and postoperatively, �� patients with postoperative deterioration, �� one patient with progressive visual loss

due to glaucoma.


ease which later developed into apathy. Mental distur-

bances correlated with the presence and extent of edema

on preoperative MRI, as 27 of 31 cases presenting with

mental disturbances had moderate or extensive peritu-

moural edema. None of the patients with a normal mental

status preoperatively deteriorated after surgery. Post-

operative psychometric assessment was available in 25 out

of 31 patients with preoperative mental deficits (Table 2).

After surgery mental disturbances improved in all but

one patient with an uncomplicated postoperative course.

Nineteen patients had normal mental function, two had

slight memory and attention deficits and one patient who

had been operated for recurrent tumour suffered from

moderate short-memory and attention deficits. All these

patients regained normal daily activity. One patient with

presenile dementia did not improve. Recovery from men-

tal disturbances correlated with resolution of edema on

follow-up MRI. Two patients with major complications

(see later) had a deterioration of their mental function.

Complications

A cerebrospinal fluid (CSF) leak through the ethmoids

occurred in three patients, all being operated via a bi-

frontal craniotomy. The CSF leakage was successfully

treated by lumbar drainage in two patients but necessi-

tated surgical repair in one case. In this patient the site of

CSF leak was found in the middle ethmoidal cells. The

dural attachment of the tumour had been coagulated and

the anterior cranial fossa had not been covered with a

periosteal flap. The fistula was repaired with a galea-

periosteal flap reinforced with sutures and fibrin glue

and further postoperative course was uneventful. Three

patients had major complications. Two patients operated

via a bifrontal approach had intraoperative injury of the

ACA. One of these patients was rendered dependent due

to mental deterioration and a moderate hemiparesis and

the other died in the rehabilitation clinic two months

after surgery due to pneumonia. The third patient had

haemorrhagic infarction of the left basal ganglia that

produced a profound hemiparesis and mental deteriora-

tion three days after an otherwise uneventful surgery.

The permanent morbidity rate, other than olfactory dys-

function, was 17.9% (Table 3).

There were three postoperative deaths (Mortality rate:

5.4%). Beside the patient mentioned above, another one

had a fulminant pulmonary embolism 25 days after an

otherwise uneventful postoperative course and one pa-

tient had rebleeding after one-stage resection of a large

olfactory groove meningioma and a left-sided frontal falx

meningioma. Despite immediate surgical exploration she

did not regain consciousness and died six days after

surgery.

Follow-up results

All patients in this series had a follow-up with clinical

and MRI assessment of at least one year after surgery

(mean follow-up 5.6 years, range 1–13 years). Of the

53 surviving patients, 46 (86.8%) had resumed a nor-

mal life with either no or minor symptoms (Karnofsky

et al. [16] score: 90–100). Five patients (9.4%) re-

turned to their previous level of activity but had

major symptoms, i.e. decreased vision and short mem-

ory deficits (Karnofsky score: 70–80). Two patients

were severely disabled and required permanent assis-

tance (Karnofsky score: 40). Vision was improved in

all but two patients with preoperative visual distur-

Table 3. Intra- and postoperative complications in 56 patients with olfactory groove meningioma

Surgical approach (no. of patients) Complication No. of

patients (%)�Comment

Bifrontal (36) rhinorrhea 3 (5.4%) lumbar drainage in 2

1 reoperated

visual deterioration 1 (1.8%)

ischemic lesion 2 (3.6%) patients dependent

CN IV paresis 1 (1.8%) Temporary

venous infarction 1 (1.8%) patient dependent

death 3 (5.4%) rebleeding, pneumonia, pulmonary embolism

recurrence 5 (8.9%) see Table 4

Unilateral frontal (4) seizures 1 (1.8%) one seizure preoperative, treated with Phenhydan

Pterional craniotomy (13) anterior pituitary 1 (1.8%) transitory

insufficiency (duration 6 months)

rebleeding 1 (1.8%) conservative treatment

Supraorbital ‘Key-hole’ (3) no complications

� Percentage given of all patients in this series.


bances. One of these patients had progressive visual loss

due to glaucoma.

Four recurrences of de novo meningiomas were ob-

served, 1.5–8 years after the first surgery (Table 4). All

tumours were progressive in growth and had to be reop-

erated. In addition, one patient who had been operated

33 years ago had a recurrent bifrontal tumour infiltrating

the entire frontal cranial base and extending into the

nasal cavity. The tumour was resected including the dura

and infiltrated bone (Simpson grade I) but a second

recurrence was observed on routine MRI follow-up in

the ethmoidal air cells and nasal cavity four years later

(Fig. 4). This tumour was radically removed by mem-

bers of the otolaryngology department via a lateral rhi-

notomy approach.

Histological examination

The meningioma was of the meningothelial subtype in

31 patients, fibroblastic in 14, transitional in 6, psammo-

matous in 4 and atypical in one case. The histological

subtype did not correlate with the invasiveness of the

tumour.

Discussion

From June 1990 to June 2003, 1011 intracranial

meningiomas have been microsurgically treated in our

institution, among them 56 meningiomas with predomi-

nant origin from the olfactory groove. The incidence of

these tumours was thus 5.5% of all intracranial menin-

giomas which is comparable to a figure of 5.4–10%

given in the literature [8, 29, 33, 40, 41, 43].

Clinical presentation

Mental and personality changes were the most com-

mon presenting symptoms in our study (39.3%) and

were found in 55.4% of the patients on clinical exam-

ination. Changes of the mental status are reported as a

primary symptom in 20.7–71% of patients harbouring

an olfactory groove meningioma [3, 8, 28, 36, 40, 43].

Euphoria was seen in 59.1% of patients in the series of

Solero et al. but was seldom seen in other investigations

including our own [3, 40]. However, an early phase of

aggressiveness which later developed into apathy has

been reported and was observed in four of our cases

[3]. As pointed out by Cushing and Eisenhardt [8], im-

paired sense of smell is rarely a reason to consult med-

ical advise. Decreased olfaction was appreciated by 14

of his 29 patients, being possibly the primary symptom

in only three of them. Bakay did not observe decreased

olfaction as a presenting symptom in his series [2].

Preoperative anosmia was noted on clinical examination

in 53.8–100% of patients in previous studies [2, 15, 23,

40, 43]. Disturbance of olfaction was the presenting

symptom in 14.3% of our patients and was found in

71.7% of the cases on clinical examination. Visual im-

pairment is a common finding, being present in 15.3–

58.1% of the patients preoperatively [3, 8, 15, 23, 40, 41,

43, 44]. It was found in 21.4% of our patients on ad-

mission and was either caused by tumour encroachment

into the optic canals, direct compression of the optic

nerves and chiasm by a large tumour or increased intra-

cranial pressure due to a sizeable tumour causing bilat-

eral papilledema. Classical Foster–Kennedy Syndrome,

described in 1911 in a patient with a bilateral olfactory

groove meningioma was not observed in this study [18].

It is reported to occur in 0–5.5% in more recent series

[2, 36, 40].

Surgical approach

The first successful resection of an olfactory groove

meningioma was performed by Francesco Durante in

1885 via a left frontal craniotomy in a 35 year old woman

[12]. This patient had left-sided anosmia and exophthal-

mus as well as memory deficits prior to surgery. Al-

Table 4. Analysis of recurrences observed in this series

Patient

no.

Sex=age

(yr)

Surgical

approach

Simpson

grade�Site of

recurrence

Histology�� Time after

first surgery (yr)

Comment

1 F=40 bifrontal II fronto-medial atypical 8% Ki þve cells 1.5 reoperated

2 F=68 bifrontal I ethmoidal cells

nasal cavity

fibroblastic 4�� first surgery 33 years

ago, reoperated

3 F=58 bifrontal I right ethmoidal cells meningiothelial 4.5 reoperated

4 F=33 bifrontal II crista galli falx cerebri fibroblastic 5.5 reoperated

5 F=47 bifrontal II cribriform plate meningothelial 8 reoperated

� Extent of resection at first surgery, �� histology of tumour at first surgery and after revision was identical in all cases, �� recurrence after second

surgery.


though displaying temporary rhinorrhea she remained in

good condition for twelve years after the operation [8,

12]. A unilateral frontal approach and uncapping of the

tumour by wedge excision of part of the frontal lobe was

preferentially performed by Cushing and Eisenhardt [8],

Dandy [9], Olivecrona [29], Poppen [32], Solero et al.

[40] and Symon [41]. In 1938, T€oonnis recommended a

bifrontal bone flap without resection of frontal lobe tis-

sue. The frontal sinus was not opened during craniotomy

and the tumour was resected via an interhemispheric

route after ligation of the superior sagittal sinus and after

incising the attachment of the falx to the crista galli [42].

Bifrontal craniotomy with opening of the frontal nasal

sinus and a subfrontal route to the meningioma has been

used with success by several investigators [13, 14, 20,

26, 28, 36]. This approach provides a good overview of

the anterior skull base for resection of bilateral, broad-

based tumours including their dural attachment and infil-

trated bone. It gives the surgeon access to the ethmoidal

air cells or nasal cavities when these sites are involved.

This approach can be combined with a lateral rhinotomy

for radical tumour resection as performed in two of our

patients and described by others [5, 21, 31]. The large

galea-periosteal flap obtained with this approach can be

used for reconstruction of the anterior skull base to pre-

vent CSF leakage [26]. However, ligation of the anterior

end of the superior sagittal sinus, usually routinely per-

formed using this approach seems to have an infrequent

but significant risk of producing venous infarction [1].

To reduce this risk it is important to ligate the sinus

immediate beneath the foramen caecum. Seeger has

proposed a unilateral basal approach with preservation

of the superior sagittal sinus [37]. However, complica-

tions related to frontal bridging veins are not eliminated

in his exposure. Kempe [17] in 1968 has extended a

unilateral frontal craniotomy to the temporal region for

tumours with predominant posterior extension. To antici-

pate complications from the frontal venous system and

from opening of the frontal sinus, Hassler in 1989 has

proposed the pterional approach for these tumours,

which was also routinely used by Yas�argil [15, 47]. All

11 tumours in Hassler’s series could be completely re-

moved and no surgical complications were encountered.

Release of CSF from the optic and carotid basal cisterns

decreases intracranial pressure and facilitates tumour

removal by this approach. Early control of the optic

nerve and carotid artery and its branches at the posterior

pole of the tumour helps preserving these structures

[15, 44]. This is an important aspect because most fatal

complications reported in the literature are caused by

injury of the ACA which is masked behind the main

bulk of the tumour and is encountered late during the

frontal approach [3, 34, 40]. This complication was

seen in two of our patients with unsatisfying outcome.

No permanent complications were observed in 13 cases

in our series treated via the pterional approach. This

approach, however, has limitations in tumours with

gross infiltration of the anterior skull base and tumours

extending into the ethmoids and nasal cavity. Adequate

fronto-basal repair and removal of tumour in a deep

olfactory groove is difficult without significant frontal

lobe retraction. It has to be noted, that the depth of the

cribriform plate has varied anteriorly between 1 and

16 mm and posteriorly between 1 and 10 mm, in anatomic

studies [19]. Sekhar and Tzortzidis recommends an ex-

tended fronto-temporal craniotomy and orbital osteotomy

(one-and-a-half approach) to minimize frontal lobe

retraction and to secure the ACA and optic nerve early

during operation [38]. Following this approach, the

anterior and posterior ethmoidal arteries can be ligated

to interrupt the main blood supply to the tumour. Divi-

sion of these vessels after subperiorbital dissection of

the supero-medial wall of the orbit has been described

without orbital osteotomy and from our experience an

orbitotomy is not necessary in these tumours [24]. Dif-

ferent surgical approaches have been used in our pa-

tients and the tumour could be resected completely

and successfully with each of them. A Simpson Grade

I resection, however, was achieved almost exclusively

via the frontal route. Also, repair of the anterior cranial

fossa and removal of subbasal tumour extensions were

facilitated using this approach. Retraction of the fron-

tal lobes is minimized provided that the lower crani-

otomy border is flash with the anterior cranial floor. It

has to be noted that all recurrences observed in this

series, had a prior bifrontal approach and two of these

had a Simpson Grade I resection. Also, most compli-

cations encountered in this series were recorded in

patients who had a subfrontal resection of their menin-

gioma (Table 3). It has to be taken into account that

tumours which were resected via a bifrontal craniot-

omy were usually large and always bilateral. The bi-

frontal craniotomy group also included all cases with

extensive drilling of the anterior cranial base and tu-

mours invading the ethmoids and nasal cavity. Interest-

ingly however, none of the CSF fistulas observed in this

series have occurred in these latter patients supporting

the view that this complication can largely be prevented

by meticulous covering of the frontal cranial base after

tumour resection [10, 11, 26, 36].


Olfactory function

Olfaction is an important sense with regard to life-qual-

ity and it has rarely been systematically investigated after

resection of olfactory groove meningiomas [45, 46]. Pre-

servation of olfaction has generally been disappointing in

these tumours [30, 41]. Indeed, all patients in our series

with preoperative anosmia remained anosmic on post-

operative follow-up even though the olfactory tract was

in anatomic continuity after tumour removal in some

cases. This included all patients with gross infiltration

of the skull base or tumour extension into the ethmoids

or nasal cavities. Anosmia may be caused by ischemia due

to deprivation of the blood supply to the olfactory nerves

or transection of the fila olfactoria during surgical ma-

nipulation. Other reasons might be degeneration of the

olfactory nerve cells by long standing compression of a

slowly evolving mass lesion or frank tumour infiltration

of the structures subserving olfaction. Nonetheless, pre-

servation of olfaction is worth attempting in patients

with normal or reduced olfaction preoperatively. In these

cases an intact arachnoid layer and viable olfactory

structures may be identified intraoperatively at least on

one side and thus protected. Although the olfactory sys-

tem and its arachnoid cistern can usually be delineated

on coronal MRI in normal subjects these structures are

obscured in patients with olfactory groove meningiomas

[6]. The presence of viable olfactory structures can

therefore only be appreciated during surgical exposure.

In this series, the sense of smelling was fully or partly

preserved in ten patients. Two patients even reported an

amelioration of their sense of smelling postoperatively

which was confirmed on semiquantitative testing. Fron-

tal lobe retraction should be kept to a minimum to pre-

vent tearing of the fila olfactoria at the level of the

cribriform plate. No difference in the rate of preserving

olfaction was observed with the various surgical ap-

proaches in our patients. Nonetheless, a unilateral sur-

gical approach is preferable leaving the contralateral

olfactory system undisturbed.

Mental disturbances

In the series of Bakay and Cares 8 of 17 patients with

preoperative mental disturbances showed definitive im-

provement on postoperative follow-up [3]. Solero and co-

workers reported that only 38.3% of their patients were

mentally normal before surgery. This figure increased to

81.6% postoperatively [40]. Ojeman, in reviewing his

series of 19 patients harbouring an olfactory groove me-

ningioma found that preoperative mental disturbances

and personality changes usually completely recovered

after tumour removal [27]. These results are confirmed

by others and in the present study [15]. In our series the

severity of mental deficits was related to tumour size and

the extend of bifrontal edema on T2-weighted pre-

operative MRI. Improvement of the mental status was

observed in all but one of our patients with an uncom-

plicated postoperative course. Amelioration of mental

function correlated well to the disappearance of perifo-

cal edema on follow-up MRI.

Recurrences

A complete removal of the olfactory groove menin-

gioma was achieved in 67–100% in different series

[3, 15, 26, 27, 34, 40, 41, 43]. Data on the recurrence

rate of these tumours give conflicting results. Several

authors have reported a very low recurrence rate [7, 27,

34, 41, 44]. Ojeman had no recurrences in his 19 patients

after an average follow-up period of 4.4 years [27]. Chan

and Thompson observed no recurrence with a Simpson

grade I and II resection after a mean follow-up of 9 years

[7]. Other series, however, have reported a high recur-

rence rate of up to 41% at 10-years follow-up in these

tumours [25, 43]. The rate of recurrence seems to be

proportional to the time period of follow-up [22, 25,

26]. We found a higher propensity of these tumours to

recur when compared to other skull base meningiomas

treated in the same institution and with a comparable

follow-up period [4]. Two of five recurrences observed

in this series had a Simpson grade I resection at first

surgery and appeared in the ethmoidal cells or nasal cav-

ity without evidence of intracranial tumour regrowth.

Tumour in these cases has probably invaded into the

paranasal mucosa and had not been removed at first

surgery although extensive drilling of the anterior floor

had been performed in at least one of these cases. These

‘en plaque’ tumour extensions may not be recognised

even on high-quality preoperative MRI because they

are obscured by the brightly enhancing mucosa after con-

trast administration. Recurrences may appear after a

long interval after an apparent radical removal, as illu-

strated by one of our cases and observed in other series

[3, 21, 43]. Cushing described invasion of the cranial

base in four patients and has covered a large opening

in the ethmoids with facia from the leg in one patient

(Case 15) with an uneventful postoperative course [8].

Poppen, in 1964 has recommended to remove any eno-

stosis found at the attachment area of the tumour [32].

Derome and Guiot [11] have found that 15% of olfactory


groove meningiomas had invaded into the paranasal

sinuses and introduced a transbasal extension of the

frontal approach for these tumours in 1972. As pointed

out by these authors extensive basal resection of in-

volved bone will invariably result in anosmia. In our

experience all patients with obvious tumour infiltration

(hyperostosis or destruction) of the anterior cranial fossa

were already anosmic before surgery. Therefore, re-

moval of infiltrated bone does not interfere with func-

tional outcome in these cases. The follow-up period in

most series, including our own, is short for this tumour

entity and data on the rate of recurrence have to be

regarded as preliminary [3, 22, 26, 27].

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Comment

This is an excellent report on the functional outcome of a series of

56 patients with olfactory groove meningiomas. This study is retrospec-

tive and with a follow-up period of 1–13 years (mean 5.6 years). The

clinical presentations accord with well known patterns. There is a high

proportion of mental disturbance. Olfactory loss was rarely reported by

the patient (14.3%) but usually found on examination (71.7%). The

tumours were often large at presentation and frequent involvement of

the skull base meant that a Grade 1 (Simpson) removal was achieved in

less than 50%. The report demonstrates that with modern methods very

good outcomes can be expected with significant improvement in mental

and visual disturbance and that preservation of olfaction should be at-

tempted in those who have normal olfaction pre-operatively. In this series

olfaction was preserved in 5 of 13 in whom it was present preoperatively.

The recurrence rate was reasonably low but as the authors point out the

follow-up period is short and with more than 50% of removals being

Simpson Grade 2 or greater then further recurrences are to be expected.

The authors give a valuable discussion of the various surgical approaches

used in this series and the method of repair of the anterior fossa floor. A

low bifrontal craniotomy with minimal frontal lobe retraction appeared

to give the best possibility for removal and anterior fossa repair.

This is a valuable contribution describing a modern series of patients

with olfactory groove meningiomas.

Peter Reilly

Adelaide

Correspondence: Hischam Bassiouni, Department of Neurosurgery,

Westpfalz-Klinikum GmbH, 67655 Kaiserslautern, Germany. e-mail:

[email protected]


olfactory groove meningiomas: functional outcome in a series treated microsurgically

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