[Schwannoma originating from the branch of the inferior oblique muscle innervated by the oculomotor nerve: a report of two cases].

Patient 1 was a 44-year-old female with a progressively enlarging orbital mass on the right side for 2 years, while patient 2 was a 25-year-old female who complained of protrusion of the right eye for 2 months. Both patients presented with exophthalmos and a palpable infraorbital mass without vision loss. Magnetic resonance imaging examination showed a well circumscribed circular orbital lesion, with hypointensity on T1 weighted image and heterogeneous hyperintensity on T2 weighted image, which could be significantly enhanced, in either eye. Both eyes were diagnosed as begin orbital tumor and received resection under general anesthesia. Intraoperatively, the distal end of the tumors was found to transmigrate to normal nerves and insert into the inferior oblique muscle. Combined with the pathological diagnosis of schwannoma and postoperative occurrence of mydriasis and inferior oblique muscle paralysis in both patients, it was confirmed that the two lesions were schwannomas originating from the branch of the inferior oblique muscle innervated by the oculomotor nerve.

[The imaging signs and significances of the enlargement of the infraorbital nerve and the frontal nerve in orbital lymphoproliferative diseases].

Objective: To describe imaging signs of infraorbital nerve enlargement (IONE) and frontal nerve enlargement (FNE) in orbital lymphoproliferative diseases (LPDs), and to explore the diagnostic value and differential diagnostic role of the signs. Methods: A retrospective case series study. The data of 222 cases (262 eyes) of LPDs and 95 cases (134 eyes) of inflammatory pseudotumors (IPs) pathologically confirmed by the Peking University People's Hospital and the Third Medical Center of the Chinese PLA General Hospital from January 2013 to December 2018 were analyzed. The LPDs were lymphoma (including atypical lymphoid hyperplasia) in 91 cases (110 eyes) and reactive lymphoid hyperplasia (RLH) in 131 cases (152 eyes). The patients with LPD included 101 males and 121 females, aged (58±17) years, and the patients with IP included 44 males and 51 females, aged (49±21) years. All patients underwent orbital CT or MRI with T1 weighted imaging, T2 weighted imaging and enhanced T1 weighted imaging scanning. Slice thickness was 3 mm. In the coronal CT or MRI, the criterion for determining IONE was the inferior orbital nerve diameter greater than the optic nerve, and the criterion for determining FNE was the forehead nerve diameter equal to or greater than the optic nerve. The pathological types and imaging features of nerve enlargement were recorded. The incidence rates of different pathological types were compared using chi-square test. Results: The enlarged nerves showed homogeneous soft tissue density on CT images, accompanied with enlarged bony infraorbital nerve grooves (foramina). MRI showed moderate signals of T1 and T2 weighted imaging, with clear boundaries and obvious enhancement, which could spread to the pterygopalatine fossa and the cranial cavity. The accompanying images included the enlargement of lacrimal glands or extraocular muscles, intraorbital mass or sinuses opacity. The IONE and/or FNE were found in 12 patients with LPD, but were not found in any patients with IP. The difference was statistically significant (12/222 vs. 0/95, χ²=5.337, P=0.021). Among the cases with nerve enlargement, there were 2 cases of diffuse large B cell lymphoma and 10 cases of RLH (2/91 vs. 10/131, χ²=3.103, P=0.078), as well as 7 cases of IgG4-related ophthalmic disease (IgG4-ROD) and 3 cases of non-IgG4-ROD (7/28 vs. 3/103, χ2=15.232, P=0.000). Conclusions: Lymphoma and RLH can express IONE and/or FNE, in which the IgG4-ROD is the most common and specific type. CT and MRI scans can show enlarged nerves and accompanying signs. Neural thickening can also be applied as a discrimination marker of LPDs and IPs. (Chin J Ophthalmol, 2020, 56: 832-838).