OBJECTIVE: To investigate the clinical manifestations, diagnosis and treatment of glioma of the intracranial segment of the optic nerve and to improve the therapeutic effect of this disease. METHODS: The clinical manifestations, CT and MRI scans, and surgical treatment results of 9 patients with optic nerve glioma in the intracranial segment admitted to our department from January 1993 to December 2006 were retrospectively studied, and the related literature in China and abroad were summarized. RESULTS: Three patients were resected by microscopic surgery through the nasal-paranasal sinus approach and six were resected by microscopic craniotomy through the pterygoid point approach; three were completely resected, four were nearly completely resected, and two were partially resected. The pathology was reported as astrocytoma grade I-II in 6 cases and grade II-III in 3 cases. 7 cases were treated with radiation after surgery. Conclusion: The disease is more common in children and young patients, and the clinical manifestations are mainly headache, visual impairment and endocrine changes. CT and MRI scans can assist in the diagnosis. Most gliomas involving only the optic nerve are of low malignancy and should be completely resected under microsurgery if possible; gliomas that also invade the optic cross are of higher malignancy and have poor results. Radiotherapy is effective in preventing tumor recurrence. The optic nerve is not really a cranial nerve anatomically, but an extension of the white matter of the brain into the orbit. Optic nerve glioma accounts for approximately 1-4% of intracranial tumors and 6% of intraorbital tumors. From January 1993 to December 2006, there were 9 cases of this type of tumor in our department, accounting for 0.8% of the patients admitted in the same period. This article summarizes the diagnosis and treatment of this disease as follows. Data and methods General data There were 4 male and 5 female cases in this group; age ranged from 8 to 26 years old, with an average of 15.6 years old. Clinical manifestations: 7 cases with decreased visual acuity and visual field changes, 3 cases with frontal and temporal headache, 2 cases with endocrine disorders, and 1 case with obesity and drowsiness. CT showed soft tissue density, thickening of the optic nerve shuttle, smooth and clear margins, and occasional calcification in some cases; in one case, a small hypointense area was seen in the center of the tumor, which was a tumor necrosis change; MRI scan showed medium or slightly low signal in T1-weighted image and medium or high signal in T2-weighted image, with obvious enhancement. The tumor location: 3 cases involved the pituitary fossa in the saddle, and the lesion size ranged from 0.8-2.0 cm; 3 cases involved the orbital apex and optic foramen; 5 cases involved the optic cross at the same time and showed occupying lesions in the saddle area. In three cases, tumors confined to the saddle on MRI were diagnosed as pituitary tumors and resected by microscopic surgery through the nasal-paranasal sinus approach. The tumor was tough and required electrocoagulation combined with blade cutting to make near total resection; 6 cases with the main part of the tumor in the saddle were operated under the microscope with pterygoid approach, and the tumor was mostly grayish white or light pink, round, elliptical or shuttle-shaped with intact envelope and no obvious boundary with the involved optic nerve. In three cases, the optic nerve was widened and thickened, and the blood supply was rich, so one case was completely resected and two cases were partially resected. The pathological examination reported 3 cases of hairy cell astrocytoma, 2 cases of oligodendroglioma and 4 cases of mixed type of both. The tumors were almost completely composed of astrocytes with perinuclear cytoplasm and protrusions filled with dense glial filaments under electron microscopy. Results and prognosis The tumors were mostly resected in 3 cases via the nasal-pterygoid sinus approach, and mostly resected in 3 cases, nearly completely resected in 1 case, and partially resected in 2 cases via the pterygoid point approach. After surgery, visual acuity improved in 2 cases, remained unchanged in 6 cases, and worsened in 1 case. After surgery, 7 patients were treated with radiation therapy at a dose of 30-40 GY. 6 patients were followed up for 1 to 13 years after surgery, 4 cases did not see any significant tumor recurrence, and 2 cases died due to tumor recurrence. Discussion The optic nerve is an extension of the white matter of the brain and is divided into intracranial and intraorbital segments. Optic nerve gliomas account for about 1%-4% of intracranial gliomas. The intraorbital segment mostly occurs in children and young patients and may present with decreased visual acuity, single anterior anterior eminence, optic nerve papillary edema or optic nerve atrophy or changes in visual field and pupil [1,2.3]. This paper discusses the intracranial segmental optic nerve glioma as follows: Age of onset and gender: Jones reported that the peak incidence of this disease is 2-6 years old, with 90% within 20 years of age. 17 cases were reported by Francis, 9 in males and 8 in females. Fan Tao et al. reported 13 cases, all of which were adolescents. Among the 9 patients admitted to our department, 4 were male and 5 were female; the mean age was 15.6 years, which shows that the tumor is more likely to occur in children and young patients, and there is no significant difference in gender. Clinical manifestations: Vision loss is the most common and main first symptom. Because the tumor occurs in the glial part of the optic nerve, it can directly destroy the optic nerve and cause vision loss. When the tumor enlarges, it forms a spherical or shuttle enlargement on the optic nerve. If the tumor progresses to the orbit, it may cause anterior protrusion of the eye, and if it progresses to the skull, it may involve the optic cross and compress the hypothalamus and pituitary stalk and cause endocrine disorders [1,2.3]. Others have reported that 9%-50% of optic nerve gliomas are associated with optic nerve fibromatosis [4]. The tumor may be confused with pituitary tumor, meningioma, and craniopharyngioma because the lesion is located in the saddle area. MRI scans have important reference value to clarify the size and location of tumor [2]. Differential diagnosis: Optic glioma needs to be differentiated from pituitary tumor, craniopharyngioma, and saddle node meningioma. Endocrine symptoms appear earlier in pituitary tumors of similar size in the saddle area, visual acuity and visual field changes occur later, there is no increase in intracranial pressure, and the pterygoid saddle may be enlarged. Craniopharyngioma has a younger age of onset, mostly with growth disturbances, and the tumor often has calcification or cystic changes. Saddle node meningioma generally has a later onset, mostly in adults, with bilateral temporal hemianopia, no bony hyperplasia and destruction of the saddle nodes on X-ray, generally no endocrine symptoms, and normal pterygoid saddle. Pathological examination: The optic nerve is an extension of the white matter of the brain into the orbit, so glioma can originate from the glial cells of the optic nerve. According to our patients and literature search, the pathological types of gliomas that involve the optic nerve alone are mostly astrocytic tumors, and some are oligodendroglial cell tumors.