Extensive extracranial growth of spheno-orbital meningioma: illustrative case

Abstract

BACKGROUND

Spheno-orbital meningioma (SOM) typically presents with a classic triad of symptoms (i.e., proptosis, visual impairment, and ocular paresis), resulting from intraorbital tumor invasion. The authors present a very rare case of SOM in which the chief complaint was swelling of the left temporal region, which, to the best of their knowledge, has not been reported previously.

OBSERVATIONS

The patient presented with marked extracranial extension to the left temporal region but unremarkable intraorbital extension, even on radiological examination. Physical examination of the patient showed almost no exophthalmos or restriction of left eye movement, consistent with the radiological findings. Four separate meningioma specimens were removed by extraction (i.e., one each from the intracranial, extracranial, and intraorbital segments of the tumor and one from the skull). The World Health Organization grade was 1 and the MIB-1 index was less than 1%, indicating a diagnosis of a benign tumor.

LESSONS

SOM may be present even in patients with only temporal swelling and few ocular-related symptoms, and detailed imaging evaluations may be required to identify the tumor.

Meningiomas are the most common benign tumors arising from the central nervous system and are approximately twice as common in women as in men.¹ World Health Organization (WHO) grade 2 and 3 meningiomas show a higher rate of brain involvement and recurrence than their grade 1 counterparts.² The MIB-1 index and Ki-67 index are used as proliferation markers, with higher values suggesting a higher WHO grade.^3,4 Spheno-orbital meningiomas (SOMs) are rare brain tumors arising from the sphenoidal ridge on the sphenoid wing and can be divided into hyperostosing sphenoid wing meningioma.⁵ This tumor is characterized by hyperostosis at the sphenoidal ridge, and previous studies have pathologically confirmed that it can directly invade bone.^6,7

SOMs typically extend intracranially and into the orbit; consequently, a large number of patients with SOM experience a classic triad of symptoms (i.e., proptosis, visual impairment, and ocular paresis).⁸ Because the tumor occupies the space within the orbit, patients with SOM often complain of progressive proptosis or visual field disturbance.^9,10 Although the tumors may extend intracranially around the sphenoid bone, extracranial extension without simultaneous eye symptoms is a very rare presentation.

In this article, we present a case of SOM in which the chief complaint was swelling of the left temporal region, but no obvious proptosis or visual field restriction were observed. We also provide images that show significant tumor extension to the temporal region without orbital invasion. Furthermore, we provide pathological evidence that all tumors removed from intracranial, orbital, and extracranial sites of the patient were meningiomas of the same origin.

Illustrative Case

A 58-year-old female presented with an approximately 11-month history of swelling of the left temporal region. She had been admitted to another department previously, and contrast-enhanced magnetic resonance imaging (MRI) at the time revealed enhanced lesions arising from the left lateral sphenoid wing with periorbital and inferior temporal involvement. In addition, the tumor showed remarkable growth into the temporalis muscle tissue. The left temporalis muscle containing the tumor was biopsied during hospitalization, and the pathologist diagnosed the tumor as an extracranial extension of meningotheliomatous meningioma. The MIB-1 labeling index was approximately 2%.

The patient was then admitted to the Department of Neurosurgery, Southern Tohoku General Hospital, for total tumor resection approximately 2 months after the biopsy. Physical findings on admission included apparent swelling of the left temporal region. Neurological findings on admission indicated only a slight left oculomotor limitation in the upward and downward directions. Although we examined the patient for other symptoms that are considered the main characteristics of SOM, we found no evidence of proptosis or visual field abnormality. Preoperative MRI and computed tomography (CT) sequences (Fig. 1A–C) demonstrated the presence of bony abnormalities in the sphenoid ridge, posterior wall of the orbit, and temporal bones. Magnetic resonance images showed a large tumor in the sphenoid wing (29.0 mL, 42 × 30 × 46 mm) with infiltration into the periorbital (1.4 mL, 22 × 18 × 7 mm) and infratemporal fossa soft tissue (39.6 mL, 55 × 80 × 18 mm). Combined with the neurological and radiological findings, these results indicated SOM.

FIG. 1.

Pre- and postoperative MRI sequences, CT scans, and 3-dimensional CT reconstructions. A: Preoperative contrast-enhanced T1-weighted image before surgery showing a large tumor in the sphenoid wing with infiltration into the periorbita and infratemporal fossa soft tissue. B: CT scan confirming hyperostosis of the left lateral sphenoid wing. C: Three-dimensional CT reconstruction of the same CT scan depicted in panel B, showing extracranial involvement of the meningioma into the left temporal fossa (green area). Magnetic resonance image (D) and CT image (E) obtained 3 months after the operation, showing almost complete removal of the tumor.

We performed a large left frontotemporal craniotomy and gross total resection of the meningioma. The extent of skull resection was determined according to the navigation system (Stealth Station S8, Medtronic). The zygoma was palpated deep into the temporal fat pad, and the extracranial portion of the tumor was found to have broken through the temporalis muscle. The tumor was removed while the temporalis muscle was retracted from the skull. The extracranial bone plate showed many small pores and bled easily; these symptoms were also observed up to the temporal base. We exposed the skull from the orbital rim to the zygoma and performed a craniotomy, including the suspected area of abnormal bone. The extent of the intradural tumor was identified using the navigation system. After opening the dura mater, we resected the tumor and its attached dura mater. Although there was strong adhesion between the tumor and the temporal cortex, we were able to carefully separate the two. At this stage, the sphenoid margin and the anterior clinoid process were preserved. Then, we removed periorbital bone to resect the intraorbital tumor. The appearance of the periorbital bone was also tumorigenic. Then, we additionally resected the sphenoid ridge and the anterior clinoid process while preserving the second and third branches of the trigeminal nerve. The tumor origin was finally removed with the dura mater, taking care to preserve the sphenoparietal sinus. The resected dura mater was reconstructed from the temporal base side, using the fascia of the rectus abdominis muscle that had been harvested beforehand. We applied a titanium plate to form the posterior orbital wall, followed by cranioplasty with a titanium mesh plate. The defect in the temporalis muscle caused by resection of the extracranial tumor was reconstructed with subcutaneous fat from the abdomen.

Postoperative CT and MRI showed almost complete removal of the tumor, including the lesions in the floor of the middle fossa and those in the intraorbital and temporal extracranial regions. Contrast-enhanced MRI was performed 1 day and approximately 3 months after the surgery and showed no recurrence of the meningiomas at the original sites (Fig. 1D–E).

We extracted 4 separate specimens from the tumor (i.e., one each from the intracranial, extracranial, and intraorbital segments of the tumor and one from the sphenoidal bone flap). The specimens were subjected to pathological examination promptly after surgery. The pathologist in our department diagnosed all tumors as meningothelial meningiomas (WHO grade 1) approximately 1 week later. The intracranial segment was composed of bundles of short spindle-shaped tumor cells with acidophilic cytoplasm and medium-sized, slightly irregular, round and oval nuclei, showing whorl formation. Infiltration of the dura mater was also observed. Nuclear atypia and mitosis were rare, and the MIB-1 index was less than 1%. Therefore, although the tumor was extremely infiltrative, there was no evidence of malignancy based on the cellular findings. The extracranial segment also showed a high degree of tumor cell invasion and proliferation, as described above. Images of hematoxylin & eosin– and MIB-1–stained histopathological specimens of the extracranial segment tissue are presented in Fig. 2. There was also a high degree of invasion into the muscle layer. The intraorbital segment showed a high degree of tumor tissue infiltration into the spongy bone. The skull showed massive tumor cell infiltration and growth in the bone marrow.

FIG. 2.

Images of extracranial tumor specimens stained with hematoxylin & eosin (H&E) (left) and MIB-1 (right). H&E staining showed a high degree of tumor cell invasion and proliferation. MIB-1 index was less than 1%.

Discussion

Observations

In this article, we presented a rare case of SOM with marked extracranial extension to the left temporal region but unremarkable intraorbital extension, even on radiological examination. Physical examination of the patient showed almost no exophthalmos or restriction of left eye movement, which was consistent with the radiological findings.

In general, meningiomas are benign tumors with a good prognosis, but those presenting with bone invasion are more likely to be malignant.¹¹ A previous report showed that the MIB-1 index of extracranial tumors was higher than that of intracranial tumors.¹² In this case, the SOM showed remarkable extension to the temporal region with little intracranial extension. This extracranially extended tumor tissue showed pathological findings similar to those of the other tumor segments. Surprisingly, the WHO classification was 1 and the MIB-1 index was less than 1%, indicating a diagnosis of a benign tumor.

When considering cosmetic aspects, there are several techniques for removing intraorbital tumors including SOM, such as the lateral orbitotomy approach,^9,13 modified lateral mini-orbitotomy,¹⁴ and lateral canthotomy orbitotomy.¹⁵ In particular, modified lateral mini-orbitotomy has fewer postoperative neurological complications and lateral canthotomy orbitotomy is cosmetically superior because it does not require removal of bone. In the present case, however, the tumor extended beyond the cranium and invaded the temporalis muscle, necessitating extensive exposure of the temporalis muscle and zygoma. Although cosmetically inferior to the techniques described above, we consider that the surgical procedure in the present case was appropriate.

Cranial reconstruction techniques have been ingeniously developed since antiquity and continue to be updated through to the present day.¹⁶ Most cosmetic reconstructions involve titanium mesh implantation or abdominal fat grafting.¹⁷ These procedures can minimize postoperative enophthalmos and the extent of dead space. Recently, computer-aided design and manufacturing implants could be created based on CT images to minimize cosmetic changes after surgery.¹⁸ In addition to addressing the cosmetic aspects, it is necessary to prevent exposure of the implants and postoperative infection to the greatest extent possible, since various materials have been developed to reconstruct the extracted skull.¹⁹ In the present case, we used a titanium mesh plate and abdominal fat grafting, as described above, to minimize postoperative cosmetic changes.

It is important to note the pitfalls related to the surgical technique in this case. We list 4 points. First, we might have filled the defect with excess fat, causing a mass effect. Second, it was difficult to preserve the sphenoparietal sinus. Third, it is possible that the periorbita was extensively tumorized, resulting in insufficient removal of the intraorbital tumor. Finally, the extent of the temporal craniotomy was small, which might have caused postoperative brain swelling.

Lessons

We expected the tumor in this case to have high intraorbital and intracranial invasion given the very extensive extracranial invasion. Although we considered additional radiation therapy depending on the histopathological diagnosis, surprisingly, the MIB-1 index was low. Therefore, we decided to follow up the clinical symptoms and images closely based on the histopathological results. It is important to note that SOM may be present even in patients with only temporal swelling and few ocular-related symptoms and may require detailed imaging evaluations.

Disclosures

The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

Author Contributions

Conception and design: Saito, Nishimura. Acquisition of data: Saito, Nishimura. Analysis and interpretation of data: Saito, Nishimura. Drafting of the article: Saito, Nishimura. Critically revising the article: Nishimura, Takemura, Matsushima. Reviewed submitted version of the manuscript: Nishimura. Approved the final version of the manuscript on behalf of all authors: Saito. Administrative/technical/material support: Nishimura, Okuyama, Kubota, Matsuyama, Sakuma. Study supervision: Nishimura, Watanabe.