Lateral orbitotomy approach for removing hyperostosing en plaque sphenoid wing meningiomas. Description of surgical strategy and analysis of findings in a series of 88 patients with long-term follow up

Abstract

Background: Sphenoid wing meningiomas extending to the orbit (ePMSW) are currently removed through several transcranial approaches. Presenting the largest surgical cohort of hyperostosing ePMSW with the longest follow up period, we will provide data supporting minilateral orbitotomy with excellent exposure for wide resection of all compartments of the tumor.

Methods: A retrospective survival analysis is made of the data cumulated prospectively during a period of 34 years, including 88 cases of ePMSW with a mean follow up period of 136.4 months. The impact of preoperative variables upon different outcome measures is evaluated. Standard pterional craniotomy was performed in 12 patients (C) while the other 76 cases underwent the proposed modified lateral miniorbitotomy (LO).

Results: There were 31 men and 57 women. The age range varied between 12 and 70 years. Patients presented with unilateral exophthalmos (Uex) ranging between 3 and 16 mm. Duration of proptosis before operation varied between 6 months and 16 years. The status of visual acuity (VA) prior to operation was: no light perception (NLP) in 16, light perception (LP) up to 0.2 in 3, 0.3-0.5 in 22, 0.6-0.9 in 24, and full vision in 23 patients. Postoperatively, acceptable cosmetic appearance of the eyes was seen in 38 cases and in 46 mild inequality of < 2 mm was detected. Four cases had mild enophthalmos (En). Among those who had the worst VA, two improved and one became almost blind after operation. The cases with VA in the range of 0.3-0.5 improved. Among those with good VA (0.5 to full vision), 2 became blind, vision diminished in 10, and improved or remained full in the other 35 cases. Tumor recurrence occurred in 33.3% of group C and 10.5% of group LO (P = 0.05). The major determinant of tumor regrowth was the technique of LO (P = 0.008).

Conclusion: Using LO technique, the risky corners involved by the tumor is visualized from the latero-inferior side rather than from the latero-superior avenue. This is the crucial milestone to achieve aggressive removal of all the involved compartments of the lesion. Satisfactory cosmetic result is reported using mini LO technique after widely exposing and removing the hyperostotic bone down to the subtemporal fossa with only simple repair of the dura without cranioplasty.

Keywords: Lateral orbitotomy; meningioma; orbital tumors; proptosis; spheno-orbital meningioma; sphenoid wing meningioma; unilateral exophthalmos..

Figure 1

Line of incision, before the patient was anesthetized and head fixed. Shaving the hair is not necessary

Figure 2

Three dimensional bone formatted CTS of the skull along with the skull X-ray adjusted for each, defining the gates through which the hyperostotic bone is visualized (a and b black arrows in the circles) and the avenues through which the instruments can better reach the depth to remove decompress the involved/hyperostotic bone (black triple arrows in c, d and e), and the black triple arrows when approaching via standard/pterional craniotomy (f) the view when is operated through the traditional pterional approach

Figure 3

The schematic drawing showing the rim of the orbit removed and refixed at the end (green shaded) and the segments of the hyperostotic bone, which is necessary to be drilled out in most of the cases to achieve complete excision of the possibly involved bony compartments around the SOF down to the inferior orbital fissure and to decompress the optic canal from the lateral side (red shaded)

Figure 4

(a and b) contrast enhanced CTS and MRI showing the intraorbital, temporal intra- and extra-cranial (small white arrow) of the tumor, c and d) three dimensional imaging of the face demonstrating the pattern of EX in (c), and bony cavity of the orbits showing asymmetric orbital fissures and squeezing of the left orbital fissure by the hyperostotic lesser and greater wings of the sphenoid bone (black arrow) in (d). (e) is the coronal view mainly illustrating the hperostotic ACP while (f) demonstrates hyperostosis of lesser and greater wings of the sphenoid bone and asymmetric orbital fissures. (g) is the lateral view of DSA showing the tumor blush located in the anterior temporal region. It is mainly fed through the meningeal branches of the ascending pharyngeal artery and the cavernous branches of the internal carotid artery and recurrent meningeal branches of the ophthalmic artery

Figure 5

(a and b) horizontal and coronal views of CTS hyperostotic wings of the SW and temporal squamosal plate and asymmetric orbital fissures squeezed in the left side without affection of ACP, (c and d) contrast-enhanced MRI elucidating a thin layer of tumoral tissue enhancement along the SW and subfrontal dura, underneath the temporalis muscle and highly suspicious for extending into the orbit. There is a bright sclerotic thickening within the posterior ethmoid sinus in the left side (black star in a) and an enhancing soft tissue nodule located in rather the same area in the ethmoid region visible in MRI (c, white arrow)

Figure 6

(a and b) contrast-enhanced CTS available from the first admission showing the hyperostotic SW the tumor mass in the temporal and subfrontal regions before craniotomy, (c) contrast enhanced CTS in the 2nd admission showing the remainder of the hyperostotic ridge, enhancing tumor and persisting EX, (d and e) contrast-enhancing T1W coronal MRI in the 2nd admission demonstrating the site of previous craniotomy and bulging SW involved by the tumor recurrence, (f and g) CTS performed after second intervention via the lateral approach showing appropriate bony decompression of the orbit and regression of EX, (h) MRI confirming tumor remnant within the cone of the orbit, and (i and j) face of the patient after long follow-up with good cosmetic features and no atrophy of the temporalis muscle

Figure 7

(a) Showing the minimal cosmetic effect of the incision on the face and (b and c) the amount of bone work performed deep to the skull base region without bone reconstruction in 3DRCTS. Minimal displacement of the bone strut did not produce any disfiguring