Treatment Practices in Optic Nerve Glioma

*Rashmi Singh, Anup Kumar, Payal Raina, Rajanigandha Tudu and Praveer K.S. Munda*

### **Abstract**

Optic nerve glioma (OPG) is a rare tumor in children and adolescents. It comprises 1–5% of central nervous system tumors. It can be sporadic or associated with the neurofibromatosis 1 (*NF1*) gene. These are usually slow-growing tumors and may remain localized to the optic nerve or can have encroached upon adjoining structures like optic chiasma, opposite optic nerve, and hypothalamus. So, there may be decreased or loss of vision, proptosis, focal neurological symptoms, precocious puberty, and short stature. Due to the involvement of these critical structures, its treatment should be based on multidisciplinary consensus. The treatment modalities include surgery, RT, and chemotherapy. The aim of the treatment should be to preserve vision. However, the timing and selection of optimal treatment modalities are always a clinical dilemma. Recently, there have been promising results with newer techniques of radiotherapy and chemotherapy.

**Keywords:** optic nerve glioma, pediatric optic glioma, radiotherapy in optic glioma, challenges in treatment in optic glioma, optic glioma and neurofibromatosis 1

#### **1. Introduction**

Optic nerve glioma (OPG) is a rare tumor comprising 1–5% of central nervous system tumors [1]. Child and adolescent patients are most commonly affected [2]. Depending upon the tumor extent as to optic chiasma, hypothalamus, there are symptoms like vision loss, proptosis, hydrocephalous, focal neurological symptoms, precocious puberty, and short stature. Location and also, the volume of the disease are determinants of prognosis. As gliomas limited to only optic nerve (OPN) have better long-term visual outcomes than those with post-chiasmatic disease [3].

OPG has been associated with the neurofibromatosis 1 (NF1) gene in 50–60% of cases [4]. It has been observed decreased visual acuity is a more common presentation in non-NF1 patients than in NF1 positive (90% vs. 72%). However, proptosis has been found in 20–30% of cases with NF1+ and, only in 5–12% cases with non-NF1 [5].

Natural history and growth patterns have been variable for this tumor [6]. Some remain stable for years, while others demonstrate slow or rapid growth patterns.

### **2. Diagnosis**

OPG is a radiological and clinical diagnosis. It is a type of tumor where pretreatment tissue diagnosis is not mandatory [7]. A biopsy is limited to cases with unusual clinical and imaging findings. Pilocytic astrocytoma is the most common histopathological variant observed, pilomyxoid astrocytoma and grade II diffuse fibrillary astrocytoma are other variants [8].

A detailed ophthalmological examination including visual clinical examination, fundoscopy, Goldmann visual field, and imaging studies (CT/MRI orbit and brain) [9], all are vital in knowing the tumor extent, response to treatment, and prognosis.
