Olfactory Groove Meningiomas: Comparison of Extent of Frontal Lobe Damage after Lateral and Bifrontal Approaches

Objective: Numerous surgical approaches have been described in the literature for successful removal of olfactory groove meningiomas. Lateral (pterional/ frontolateral) and anterior (bifrontal/ fronto-orbito-basal) approaches with their various modifications remain the two main philosophies in encountering them. In this study, we discuss our experience in microsurgical treatment of these tumors at our institution and assess the extent of frontal lobe damage after the resection of tumor. We also discuss other controversies in management and outcomes in the literature.

Methods: We reviewed the medical records of patients who underwent surgical excision of olfactory groove meningiomas from 1990 to 2014. To measure the extent of frontal lobe damage via lateral and anterior approaches, we measured the volume of porencephalic cave in the post-operative MRI in Brainlab software. The ratio of volume of porencephalic cave to tumor was measured between two sides and two approaches.

Results: Fifty-seven patients with olfactory groove meningiomas, who underwent 62 microsurgical resection procedures in 1990–2014, were included in the study (74% was more than 5 cm at presentation). Pterional and bifrontal craniotomies were the most commonly used approach. Olfactory preservation was better with lateral approaches (p = 0.04) and size of tumor smaller than 5 cm (p = 0.0005) The ratio of volume of porencephalic cave to the volume of tumor (R) was significantly less in contralateral side for tumor of all sizes (p = 0.0005 for tumor <3 cm, p = 0.0087 for tumor 3–5 cm, p = 0.0209 for tumor>5 cm) when compared with ipsilateral side. As anticipated, there was no significant difference in this ratio between ipsilateral and contralateral side for the bifrontal craniotomy group. Comparing the two approaches, the ratio (R) was not different for the 3–5 cm tumor subgroup in ipsilateral or contralateral side or when the total volume was considered. However, it was significantly different for dominant lobe and total volume in the subgroup with tumors larger than 5 cm (p = 0.0002 and 0.015 respectively).

Conclusions: Lateral approaches (pterional/ fronto-lateral) resulted in less frontal lobe damage and more olfaction preservation in comparison to anterior approaches in present series.

Table 1 Demographics of the patient cohort

sex	male	23
	female	34
age		58.82
Pre-op KPS		75.6
Post-op KPS		86.4
Follow-up		6–160 month

Table 2 Genome-wide association studies and hepatitis C

Clinical features	No of patients (%)
Headache	33 (57.89)
Anosmia	30 (52.63)
Mental changes	25 (43.85)
Visual impairment	22 (38.6)
Fatigue, dizziness	20 (35.08)
Gait disturbance	10 (17.54)
Seizure	7 (12.28)
Weakness	4 (7.01)
Numbness	4 (7.01)
Incontinence	4 (7.01)
incidental	0

Table 3A Tumor growth patterns

	≤3 cm	3–5 cm	≥5 cm	Total
Ethmoid invasion	0	1	4	5
Optic nerve involvement	0	3	11	14
AcoA complex involvement	0	1	3	4
	3	12	42	57

Table 3B Surgical Approaches

Approach		≤3 cm	3–5 cm	≥5 cm	Total
Primary (N = 57)	frontolateral/ pterional	3	9	29	41
	bifrontal	0	3	13	16
	TOTAL	3	12	42	57
Recurrent (N = 5)	pterional	0	0	0	0
	bifrontal	0	5	0	5
	TOTAL	0	5	0	5

Table 4 Extent of excision

Surgical approach	Simpson grade I-II	Simpson grade III-IV
frontolateral/ pterional	40	1
Bifrontal (primary+ recurrent)	18	3
total	58	4

Table 5 Pathological grading of the tumors (at primary resection)

WHO	≤3 cm	3–5 cm	≥5 cm	Total
I	3	10	36	49
II		2	6	8

Table 6 Complications

Complications	Frontolateral/pterional	Bifrontal	Total
CSF leak	0	2	2
meningitis	1	1	2
Wound infection	1	2	3
hydrocephalus	3	0	3
death	0	0	0

Table 7 Assessment of functional status after tumor resection

Function	Outcome
Vision	Improved	15
	Same	7
	New deficit	0
	No complaints in pre/ post-op period	35
Olfaction	Improved	0
	Preservation	31 (26/41 in lateral approaches and 5/16 in bifrontal approaches)
	Could not be preserved	26
Cognition	Improved	17
	Same	8
	New deficit	0
	No complaints in pre/ post-op period	32

Table 8 Measurement of porencephalic cave volume

Surgical Approach		≤3 cm	3–5 cm	≥5 cm
frontolateral/ pterional	Tumor volume(I/L)(cm3)	4.6	17.71	40.89
	Porencephalic cave volume (I/L) (cm3)	2.5	12.57	23.47
	Tumor volume (C/L) (cm3)	2.3	15.73	38.68
	Porencephalic cave volume (C/L) (cm3)	0.66	8.08	14.29
	Ratio (I/L)	0.54	0.71	.57
	Ratio (C/L)	0.29	0.52	.37
	P value	0.0005	0.0087	0.007
Bifrontal	Tumor volume (R) (cm3)	−	16.85	42.41
	Porencephalic cave (R) (cm3)	−	11.29	33.01
	Tumor volume (L) (cm3)	−	16.43	39.52
	Porencephalic cave volume (L) (cm3)	−	10.68	31.66
	Ratio (R)	−	0.67	0.77
	Ratio (L)	−	0.65	0.80
Lateral (I/L) vs bifrontal (R)	P value (of difference between ratio of porencephalic cave and tumor)	−	0.65	0.04
Lateral (C/L) vs bifrontal (L)	P value (of difference between ratio of porencephalic cave and tumor)	−	0.08	0.0001
Lateral vs bifrontal (total volume)	P value (of difference between ratio of porencephalic cave and tumor)	−	0.57	0.001

Fig. 1

Fig. 2