Abstract

Background: Intraosseous meningiomas and cystic meningiomas are two rare subtypes of meningiomas. Meningiomas can develop with characteristics encompassing both cystic and intraosseous, termed intraosseous cystic meningiomas, that pose a diagnostic challenge.

Case Description: We report the case of a 41-year-old woman with a history of hearing loss presented with a left frontal mass that had been present for 12 years. Her history of hearing loss was in the setting of ear infections bilaterally since she was a teenager and was being evaluated by ear, nose, and throat specialists at the time. Initial cranial computed tomography (CT) identified a skull lesion characterized as a benign arachnoid cyst. At that time, no further intervention was deemed necessary. During a future visit with her primary care physician, the patient expressed concern about the potential growth of the mass and a new symptom. This prompted further CT and magnetic resonance imaging (MRI) studies of the brain, and a benign etiology such as an intra-diploic arachnoid cyst was suspected, but the patient was referred to neurosurgery for further evaluation. The patient and neurosurgeon came to the shared decision for surgery, given ongoing symptoms and pursuit of diagnosis. On the day of the operation, a left parietal craniectomy was performed using stereotactic navigation. At follow-up, the patient noted improvement in headache symptoms and was scheduled for a follow-up MRI.

Conclusion: This case provides our rare example of a patient presenting with intraosseous cystic meningioma and current reported cases in the literature. The exact natural history of this pathology is not well described, and further research is needed.

Keywords: Case report, Cystic meningioma, Intraosseous cystic meningioma

INTRODUCTION

Meningiomas are slow-growing lesions originating from the meningothelial cells of the arachnoid layer of meninges. Accounting for 36.6% of all primary brain tumors, with an incidence of 8.3/100,000 persons,[ 15 ] they represent the most common primary brain tumor.[ 1 ] Although meningiomas are typically benign tumors, their existence does not mean they come without consequences.[ 15 ] In patients diagnosed with grade II and III tumors, the overall 10-year survival rate sits at 53% and 0%, respectively, despite aggressive therapeutic efforts with the potential for long-term sequelae in these patients, including but not limited to personality changes and altered mental status. Common presenting symptoms include headache, focal neurological deficits, and generalized and partial seizures, though these symptoms are nonspecific.[ 1 ] While the majority of meningiomas are well circumscribed and solid,[ 12 ] rarely, they can present intraosseously with cystic features, representing 2–4% and 1–2% of all meningiomas, respectively.[ 6 , 13 ] Due to the relative rarity of these features individually, intraosseous cystic meningiomas are especially rare and can be difficult to identify.[ 3 , 8 ] Here, we present a case of intraosseous purely cystic meningioma in a 41-year-old woman presenting with a growing left frontal mass.

ILLUSTRATIVE CASE

A 41-year-old woman with a history of hearing loss presented with a left frontal mass that had been present for 12 years. She denied a history of head trauma. Her history of hearing loss was in the setting of ear infections bilaterally since she was a teenager and was being evaluated by ear, nose, and throat specialists at the time. Her last infection was over a year prior, and at the presentation, she denied ear drainage, fevers, and unexpected weight loss. Initial cranial computed tomography (CT) identified a 3 cm skull lesion characterized as a benign arachnoid cyst. At that time, no further intervention was deemed necessary. The mass persisted without headache or other associated symptoms except for intermittent regional pain.

During a visit with her primary care physician, the patient expressed concern about the potential growth of the mass and a new, occasionally pulsatile sensation in the region. This prompted further CT and magnetic resonance imaging (MRI) studies of the brain, which revealed a 4.0 × 4.5 cm cystic lesion in close proximity to the dura, with expansion of the intra-diploic space and mild internal septations suggestive of small veins within the mass [ Figures 1 and 2 ]. A benign etiology, such as an intra-diploic arachnoid cyst, was suspected, but the patient was referred to neurosurgery for further evaluation.

Figure 1:

Preoperative (1 month) computed tomography brain, post contrast, (a) coronal and (b) sagittal showing nonenhancing left frontal intra-osseous lesion that is homogeneously isodense with brain parenchyma. There is communication through the inner/deep cortical layer with the intracranial compartment.

Figure 2:

Pre-operative (1 month) MRI brain with/without contrast showing (a) left frontal intra-osseous homogenously T2 hyperintense cystic lesion (b and c)with rim-enhancement.

The patient was offered continued surveillance versus surgical resection. The patient and neurosurgeon came to the shared decision for surgery, given ongoing symptoms and pursuit of diagnosis. On the day of the operation, a left parietal craniectomy was performed using stereotactic navigation. While drilling through the outer table, a pocket of cerebrospinal fluid was encountered. Subsequently, the craniectomy was widened, and the meningocele was resected from the bone, which revealed a focal area of dehiscence of the inner bony shelf through which the cystic mass continued to the intracranial compartment [ Figure 3 ]. The inner bony table was then drilled away, and normal dura was identified circumferentially around the abnormal tissue. Subsequently, the abnormal tissue was resected to its connection point with the pia mater. After hemostasis was achieved, the dural defect was then repaired with a small Synthecel (DePuy Synthes; Warsaw, Indiana) inlay and onlay with DuraSeal (Integra; Princeton, New Jersey) on top. The craniectomy was repaired with a HydroSet set (Stryker; Kalamazoo, Michigan) and a titanium mesh plate [ Figure 4 ]. The operation concluded without complication, and the patient was transferred to the Neuro intensive care unit in stable condition for postoperative monitoring.

Figure 3:

Intra-operative photos. (a) Stealth navigation was used to outline the bony roof of the left frontal lesion. (b) The bony roof was drilled open, and the inner contents were excised en bloc. The connection via the inner bony shelf was severed, and the deeper connection subsequently explored and excised from its attachment to the brain parenchyma.

Figure 4:

Post-operative day 0 computed tomography noncontrast of (a) head coronal and (b) sagittal showing resection of meningioma and obliteration of cystic space with HydroSet and cranial plating.

Postoperative cranial CT after the procedure showed no concerns [ Figure 4 ]. The patient remained at neurological baseline and was discharged on postoperative day 1.

Pathology revealed a cystic lesion with meningothelial proliferation, entrapped bone fragments, and no significant atypical features, consistent with a central nervous system (CNS) World Health Organization (WHO) grade 1 meningioma [ Figure 5 ]. At clinic follow-up, the patient noted improvement in headache symptoms and was scheduled for a follow-up MRI in 6 months.

Figure 5:

(a and b) Routine hematoxylin and eosin stain show cystic meningothelial proliferation. (c and d) Somatostatin receptor 2 is positive in the tumor by immunohistochemical stain. Magnification: (a and b): 20x; ( c and d): 100x

Literature review

Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020 methodology[ 16 ] was used to identify relevant cases with search terms including “cystic,” “intraosseous,” and “meningioma” [ Figure 6 ]. Abstracts describing only intraosseous or cystic meningioma were excluded. Abstracts focused on other meningioma subtypes were also excluded. Identified abstracts underwent full manuscript review. An additional abstract was excluded based on not meeting the criteria of being exclusively an intraosseous cystic meningioma. The literature review identified two prior reported cases of intraosseous cystic meningioma. Information regarding patient age, sex, symptoms, location, imaging findings, surgical approach, cyst description, histology, surgical complications, and follow-up deficits were collected [ Table 1 ].

Figure 6:

Methodology from Page et al., 2021.[ 16]

Table 1:

Reported cases of intraosseous cystic meningiomas.

DISCUSSION

Meningiomas are the most common primary CNS tumor and most commonly present with nonspecific symptoms, such as focal deficits, seizures, and/or headaches, in women and older adults.[ 1 ] On imaging, they typically appear as homogeneous, hemispheric, markedly enhancing extra-axial lesions located over the cerebral convexity, in the parasagittal region, or arising from the sphenoid wing.[ 2 ] At present, the WHO classifies meningiomas from I to III based on histological features, with I being benign and most frequent, II being atypical, and III being anaplastic/malignant.[ 11 ] In addition to these guidelines, meningiomas can be further distinguished based on CNS location, such as olfactory groove, sphenoid, cavernous sinus, suprasellar, and level of resection. Despite comprehensive grading systems and the overall commonality of meningiomas, the exact etiology remains unknown.[ 17 ] While meningiomas have been associated with several hereditary conditions, including neurofibromatosis type 2, Li-Fraumeni, Gorlin, von Hippel-Lindau, Cowden disease, and multiple endocrine neoplasia type 1, their pathophysiology is poorly understood and a large focus of current research.[ 17 ]

Of the various types of meningiomas, we present a particularly rare case of an intraosseous cystic meningioma, of which there are only two known published cases. The rarity of such lesions stems from the already low incidence of meningiomas with either cystic or intraosseous features.[ 6 ]

In general, cystic meningiomas account for 2–4% of total meningioma diagnoses,[ 13 ] with most meningiomas sharing wide microscopic diversity. Like solid meningiomas, cystic meningiomas typically present with nonspecific neurologic symptoms such as headache and motor deficits. According to Nauta’s classification system, cystic meningiomas are divided into 4 types – Type I and Type II, where the tumor encompasses the cysts, and Type III and Type IV, where the cysts surround the tumor.[ 13 ] Specifically, Type III cystic meningiomas are characterized by an area of gliosis and cysts bordering the tumor, while Type IV cystic meningiomas are characterized by cysts that communicate with the arachnoid space.[ 13 ]

Overall, cystic meningiomas are challenging to diagnose. While a CT scan has high sensitivity for the diagnosis of solid meningiomas, it proves less useful in diagnosing cystic meningiomas, with a reported sensitivity of only 38%.[ 4 , 7 , 14 ] Cystic meningiomas are difficult to diagnose intraoperatively as well as studies have reported several instances of misdiagnosis with glioma based on initial surgical microscopy, ultimately requiring a second operation.[ 13 ]

Intraosseous meningiomas, too, prove rare and independently account for only 1–2% of reported meningiomas.[ 6 ] At present, the exact etiology of intraosseous meningiomas remains unknown, but researchers speculate they may arise from either abnormal differentiation or transformation of embryonal precursor and/or arachnoid cells along the skull sutures.[ 18 ] These lesions have commonly been found to occur in the frontotemporal orbits, anterior cranial fossa, paranasal sinuses, nasal cavity, neck, and petrous region of the temporal bone.[ 5 ] Involvement of the skull may render intraosseous lesions to incomplete resection.[ 5 ] Notably, intraosseous meningiomas are classified into two subtypes: osteolytic and osteoblastic.[ 10 ] Unlike cystic meningiomas, intraosseous meningiomas are well defined on CT. Osteoblastic lesions often appear as focal hyperdense lesions with prominent skull expansion, whereas osteolytic lesions appear as smaller hyperdense lesions with thinning of the surrounding bone.[ 6 ]

With both cystic and intraosseous meningiomas presenting with their own set of diagnostic challenges, diagnosing an intraosseous cystic meningioma itself can be difficult. In the literature review, we found two reported cases of cystic intraosseous meningioma diagnosed at ages 24 and 62 [ Table 1 ].

The first reported patient was a 62-year-old man presenting with swelling of the lateral wall of the left orbit. On CT and MRI, a large cystic intra-diploic lesion with a mural nodule involving the lateral wall of the orbit and a greater wing of the sphenoid was found. CT scan further identified the lesion as osteolytic with overall dimensions of 23 × 32 mm, with a substantial portion of the lesion consisting of fluid and a connected but discernable solid portion measuring 8 × 9 mm. The patient underwent surgery, and the lesion was removed without complication. The patient was discharged from the hospital after 5 days. On histological examination, the mural nodule was identified as a benign meningothelial meningioma (WHO grade I) comprising cells with oval-to-round nuclei and small nucleoli arranged in syncytial and lobular patterns without atypical or malignant features. Importantly, the cyst wall did not include cancerous cells, and the tumor did not infiltrate the fibrous or underlying bone.[ 3 ]

The second reported patient was a 24-year-old woman who presented with a 2-day history of headaches in the setting of a recent ground-level fall. Noncontrast CT demonstrated a small extra-axial hemorrhage in the right frontotemporal region of the skull, and MRI revealed a slightly rim-enhancing osteolytic lesion invading the right sphenoid bone. The patient opted for the removal of the tumor, and the procedure was performed without complication. During the procedure, the lateral wall of the right orbit, zygoma, and a thinned portion of the bone at the pterygoid process were drilled. The hematoma was evacuated, and a multiseptated cystic cavity was evident. On frozen pathology, the lesion showed single scattered or epithelioid clusters of round to elongated cells intermixed with many neutrophils. On histology, the lesion was identified as an intraosseous meningothelial and microcystic meningioma (WHO grade I).[ 8 ]

Both prior cases of intraosseous cystic meningioma were located in the sphenoid bone and presented with an assortment of nonspecific symptoms such as headaches, pain on palpation, proptosis, and general balance deficits.[ 3 , 8 ] Despite their typically benign nature, the presence of cystic features, particularly in intraosseous meningiomas, highlights the varied and sometimes unexpected presentation of these tumors.[ 18 ] Intraosseous cystic meningiomas involving the skull are difficult to diagnose because of their rarity and variable appearance on imaging.[ 10 ]

The identification of these tumors is important for accurate diagnosis and management, especially when differentiating them from other lesions that may mimic common pathologies such as metastases or high-grade glial neoplasms.[ 9 ] This highlights the importance of longitudinal follow-up in patients with resected lesions, including MRI brain scans, and educating patients about concerning “red flag” symptoms such as syncope, heart palpitations, and shortness of breath that require expedited re-evaluation.

Submission statement: This manuscript is original and has not been submitted elsewhere in part or whole.

CONCLUSION

In summary, intraosseous cystic meningiomas are an exceedingly rare pathology that poses a diagnostic challenge. A thorough history, physical, and neuroimaging can help narrow the differential, but ultimately, surgical pathology is required for diagnosis. Maximum safe surgical resection is recommended. The exact natural history is not well described, and further reports and research into this pathology are needed for a better understanding of the lesions and their outcomes.

Ethical approval:

Institutional Review Board approval is not required.

Declaration of patient consent:

The authors certify that they have obtained all appropriate patient consent.

Financial support and sponsorship:

Nil.

Conflicts of interest:

There are no conflicts of interest.

Use of artificial intelligence (AI)-assisted technology for manuscript preparation:

The authors confirm that there was no use of artificial intelligence (AI)-assisted technology for assisting in the writing or editing of the manuscript and no images were manipulated using AI.

Disclaimer

The views and opinions expressed in this article are those of the authors and do not necessarily reflect the official policy or position of the Journal or its management. The information contained in this article should not be considered to be medical advice; patients should consult their own physicians for advice as to their specific medical needs.

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