Journal of Neuro-Ophthalmology:
Primary Atypical Optic Nerve Sheath Meningioma in a Child With Restricted Diffusion on Magnetic Resonance Imaging
Nabavizadeh, S. Ali MD; Santi, Mariarita MD; Belasco, Jean B. MD; Zimmerman, Robert A. MD
Departments of Radiology (SAN), Pathology (MS), and Oncology (JBB), The Children's Hospital of Philadelphia, Philadelphia, Pennsylvania.
Address correspondence to Seyed A. Nabavizadeh, MD, Department of Radiology, The Children's Hospital of Philadelphia, University of Pennsylvania, 34th Street, Civic Center Boulevard, Philadelphia, PA 19104; E-mail: email@example.com
The authors report no conflicts of interest.
Abstract: Optic nerve sheath meningioma is most often discovered in adults and is relatively rare in children. We report a 12-year-old girl with an atypical primary optic nerve meningioma, which demonstrated restricted diffusion on magnetic resonance imaging and high Ki67 labeling index. The patient developed recurrence, despite aggressive surgical resection of primary tumor and local radiation. We are unaware of previous reports documenting this constellation of imaging and histopathologic findings.
Optic nerve sheath meningioma is a tumor arising within the nerve sheath of the orbital or intracanalicular portion of the optic nerve secondary to proliferation of meningothelial cells. This tumor may be either a primary tumor of the optic nerve sheath or more commonly secondary tumor because of extension of a primary intracranial meningioma into the orbit (1,2). Its occurrence is relatively rare in the pediatric patients and has more aggressive behavior in this population (1). We report an atypical primary optic nerve meningioma, which demonstrated restricted diffusion on magnetic resonance imaging (MRI) and high Ki-67 labeling index.
One year before admission to hospital, a 12-year-old girl noted blurred vision in her left eye, which progressed to complete visual loss with no light perception. She initially was diagnosed with optic neuritis and received a course of corticosteroids without improvement. The patient was later thought to have a “blood clot” behind her eye based on an outside imaging study and was started on enoxaparin. She continued to have pain behind her left eye and a subjective feeling of her eye being “pushed out.” She was referred to our institution, where an MRI revealed a fusiform left orbital intraconal, a mass producing moderate degree of proptosis of the left globe (Fig. 1). The mass had a homogeneously low-signal intensity on T2 images filled most of the intracranial space with evidence of intraocular invasion. Avid enhancement of the mass was demonstrated after contrast administration, which extended through the left optic canal involving the intracranial left optic nerve just anterior to the optic chiasm. The mass also demonstrated restricted diffusion (Fig. 2). The lesion was biopsied, followed by exenteration of the left orbit with reconstruction of the socket with dermal fat graft. This tumor had the histologic features and immunohistochemical staining characteristics of a meningioma. The Ki67 labeling index was at least 10% (Fig. 3). The neoplasm also demonstrated an extremely aggressive pattern of growth with invasion of the orbit, retina, and choroid and near total replacement of the optic nerve (Fig. 4). The constellation of histopathological and immunohistochemical findings was consistent with atypical meningioma.
A left orbitozygomatic craniotomy was performed for removal of the remaining tumor in the apex of the orbit, and optic canal, followed by local radiation to the tumor bed (5940 cGy). Five years later, the patient presented with tumor recurrence in the floor of the left orbit with bone destruction and extension into the left maxillary sinus. This was successfully treated with resection and radial-free flap reconstruction. The patient has had multiple neuroimaging studies and shows no signs of tumor recurrence 36 months after her last surgery. No evidence of neurofibromatosis type 2 or other meningiomas have been detected in our patient.
A significant feature of meningiomas in childhood is the higher rates of malignant and atypical subtypes in comparison with adults (3,4). In one report, 25% of all meningiomas in the pediatric population showed biological aggressive behavior in terms of disease progression (4). Our patient fit this clinical profile. The main differential diagnoses in a child presenting with an optic nerve tumor are optic nerve glioma and optic nerve meningioma. In our case, complete involvement of optic nerve and restricted diffusion on MRI was also suggestive of a primitive neuroectodermal tumor such as medulloepithelioma (5).
In the pediatric age group, literature regarding the neuroimaging appearance of primary optic nerve meningioma is scant, and no specific pattern has been recognized (1). However, most nerve sheath meningiomas in adult patients have a tubular configuration, followed by other patterns including globular, fusiform, or focal enlargement of the optic nerve sheath (1). Irregular tumor margins in the orbit are indicative of extradural invasion into surrounding tissues (1). MRI is the study of choice for evaluation of optic nerve tumors and should include fat suppression sequences and intravenous contrast (6). Lope et al (7) described the diffusion characteristics of a series of orbital tumors in pediatric patients. In one case, a meningioma demonstrated restricted diffusion; however, they did not generate apparent diffusion coefficient (ADC) values and did not determine the histological type and grade or comment about primary optic nerve meningioma vs extension form an intracranial meningioma.
Multiple studies have found a statistical significance between histopathological subtype of meningiomas and the ADC values, with a tendency for atypical/malignant tumors to have lower ADC values (8,9). Various theories have been proposed to explain the decreased ADC in high-grade tumors including increased tumor cellularity, increased nucleus/cytoplasm ratio, small cell size, fibrous, or gliotic tissues within the tumor or a combination of these factors (10). Ki-67 is an immunohistochemical cell proliferation marker that has been used to differentiate between benign and atypical/malignant meningiomas. In addition, this marker has been shown to be a more reliable predictor of both tumor recurrence and patient survival than histologic grade (11,12). A cutoff Ki-67 index of 10% has been proposed for distinguishing potentially recurrent and nonrecurrent meningiomas (12). In our patient, both restricted diffusion and Ki-67 value were indicative of the malignant nature of the tumor, which recurred despite aggressive initial resection and local radiation.
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