Intracranial schwannomas are common and account for 8–10% of all primary intracranial tumors (1). In contrast, orbital schwannomas are rare and account for only approximately 1–2% of all primary schwannomas (2). In this study, we report a case of schwannoma in children, which is a dumbbell-shaped cranial-orbital mass. The total neoplasm was successfully removed, and the pathological diagnostic result was schwannoma. Postoperatively, the patient's painless exophthalmos had completely disappeared without postoperative sequelae or visual impairment. Neither radiotherapy nor chemotherapy was performed, and no recurrences were observed for 3 months.

Schwannoma arises from Schwann cells and are known to originate from the sensory branches of the ophthalmic division of the trigeminal nerve in an orbit (3). Schwannomas occur in middle age and are usually rare in children with the absence of neurofibromatosis (4). We discussed a 12-year-old boy who had a dumbbell-shaped schwannoma, and most of the lesions were found in the left orbit with a small portion in the left cavernous sinus. Orbital schwannomas are usually oval or round, but those extending into the cranial cavity from the superior orbital fissure are usually dumbbell-shaped (5). Therefore, we speculated that it was a unique case of an orbital schwannoma in children extending into the left cavernous sinus via the superior orbital fissure.

Schwannomas are always benign and well-encapsulated nerve sheath tumors, with an insidious and slow growth pattern (6). There is no difference between genders or between the right or left eyes (3, 7, 8). Schwannomas have non-specific clinical presentations, and their primary clinical symptom is painless exophthalmos (8). They usually did not affect extraocular movements or vision unless it was big enough to compress the optic nerve, which might cause visual impairment, double vision, abnormal sensations, pain, eyelid swelling, and even vision loss (2, 9).

Microscopically, most orbital schwannomas exhibit a histopathologic feature with a biphasic morphology, including Antoni A and Antoni B patterns (10). Due to this situation, the tumor on MRI has a different degree of heterogeneity, which correlates with the dark signal of Antoni B and the bright signal of Antoni A on T1WI. However, the diagnosis of schwannomas via clinical symptoms and imaging evaluation is tricky because of the variable presentation and location (11). According to the literature, orbital schwannomas produce a hypointense signal on T1WI and a hyperintense signal on T2WI, which may be homogeneously or heterogeneously enhanced (12). CT is often the first investigation obtained, which is helpful in depicting adjacent bone destruction and calcification (13).

We conducted keyword searches in the PubMed database over the past decade, and the sets of keywords used were associated with orbital schwannoma. According to previous related rare case reports, we summarized the common location of orbital schwannomas, which was an intraocular, orbital, retro-orbital, infraorbital, trigeminal, vagal, or trochlear mass. In part, we also found a low incidence of orbital schwannomas in children, and we believed that the rarity could be explained by the slow-growing nature of this type of tumor type in some patients presenting in early adulthood (14). Though a few cases involving cranial-orbital communication were reported in the literature, we found nearly no case completely similar to our patient, a 12-year-old boy having a cranial-orbital schwannoma with a dumbbell-like appearance at the same time. Thus, we have reported this rare and unique case to enrich the information about intracranial-orbital schwannoma in children and also suggest that clinicians and radiologists should sufficiently differentiate it from other orbital tumors.

In the orbital extraocular area, optic nerve glioma is the most common tumor in children (7), whose signal is similar to that of the brain parenchyma, as in our case. However, we can ensure that the tumor is located above the optic nerve through imaging findings, which led us to rule it out. In addition, another common optic nerve disease in children is myelin oligodendrocyte glycoprotein (MOG) antibody-associated optic neuritis, characterized by visual loss and pain with eye movement (15), which is not consistent with the clinical presentation of our case. The mass in our case appears to be dumbbell-shaped, well-defined, mildly heterogeneous, and strengthening, suggesting that it may be a benign tumor with a low incidence. Thus, we hypothesized that it was a hamartoma before surgery, which usually had a clear edge, had a mildly non-uniform internal signal, hypointense and hyperintense on T1WI and T2WI, respectively, and had a slightly uneven enhancement (16). Fortunately, hamartoma and schwannoma were all benign masses and had the same surgical method, which did not delay the treatment of this child due to our misdiagnosis.

Usually, the first choice for orbital schwannoma is gross total resection (8, 17, 18). No further radiotherapy or chemotherapy is required after surgery. According to our prior recognition, only a few cases of orbital schwannoma with recurrence had been reported (19). However, we still need to follow up with the patient for a long period of time.

Our case refers to a 12-year-old boy with intracranial-orbital schwannoma. Preoperative diagnosis is difficult due to its different degrees of heterogeneity. However, early assessment and prompt management are necessary to prevent the development of severe complications. We suggest that orbital schwannomas should be sufficiently differentiated from other orbital tumors in children, despite their exceedingly rare occurrence. Our case enriches the information about this disease, enhances our understanding of this tumor, and underscores the importance of complete surgical resection.

The raw data supporting the conclusions of this article will be made available by the authors, without undue reservation.

Written informed consent was obtained from the minor's legal guardian, for the publication of any potentially identifiable images or data included in this article.

YS, QX, AC, and SC performed the material preparation, image collection, and analysis. YS wrote the first draft of the manuscript. QX supervised the initial draft and critically revised the manuscript. SC and AC analyzed the case report and critically revised the manuscript. MQ corrected the grammar in the manuscript. All authors contributed to the case report conception and have read and approved the final manuscript.