Optic nerve glioma in an adult: a rare case report

¹University Sidi Mohamed Benabdellah, Fez, Morocco

^&Corresponding author
Hassan Moutei, University Sidi Mohamed Benabdellah, Fez, Morocco

Introduction    

Optic nerve gliomas (ONGs) are rare tumors and comprise 1% of all intracranial neoplasms and 2% to 5% of central nervous system tumors in the pediatric population [1]. The clinical manifestations vary but are often characterized by unilateral visual loss, proptosis, and optic nerve atrophy [2]. Various treatment strategies are heavily debated, from close clinical observation to more aggressive surgical resection, chemotherapy, and radiotherapy depending on tumor behavior and the patient's overall conditions [3]. Publications on ONGs in adults are rare, with most information derived from case reports and small case series. It is generally accepted that ONGs in older patients tend to be more infiltrative, and are often fatal [4]. We describe the case of a 50-year-old woman with ONG who showed later onset and slower progression of the disease than is usually observed in older adults.

Patient and observation     

Patient information: a 50-year-old female with no medical history developed gradual visual impairment in her right eye (RE).

Clinical finding: the ophthalmological examination showed a visual acuity of 0.15 in the RE and 0.8 in the left eye, as well as relative afferent pupillary defect in RE. Examination showed 3mm of axial proptosis and left esotropia with mild restriction of elevation and abduction on the RE accompanied by moderate pain (Figure 1). On funduscopic examination, the right optic nerve was pale but the left appeared normal.

Timeline of current episode: the patient presented to the outpatient department on 12/02/2024, with complaints of progressive deterioration of vision in the RE. She was admitted on the same day for investigations. An ophthalmological examination and fundoscopic assessment were performed. On 27/02/2024, a magnetic resonance imaging (MRI) of the orbits was done, suggesting the presence ONG. The patient was managed conservatively and followed up regularly. After six months, on 30/07/2024, no progression of the lesion was detected, and her condition remained stable.

Diagnostic assessment: magnetic resonance imaging of the orbits revealed slightly prolonged T1 relaxation times, making the lesion appear isointense on T1-weighted images. Conversely, T2-weighted images typically showed the tumor as hyperintense, indicative of prolonged T2 relaxation times. Automated perimetry identified a visual field defect in the RE (Figure 2).

Diagnosis: based on these clinical and imaging findings, a diagnosis of right ONG was established.

Therapeutic intervention: based on the patient's overall clinical presentation, a conservative approach with close monitoring was adopted.

Follow-up and outcome of interventions: at the 6-month follow-up, an MRI showed no progression of the lesion and her visual acuity was stable in both eyes. Automated perimetry at this follow-up indicated stabilization of the visual field defect in the RE (Figure 3).

Patient perspective: the patient expressed optimism regarding the stabilization of her condition.

Informed consent: informed consent was obtained from the patient.

Discussion     

Although ONGs are usually benign in pediatric populations, their occurrence in adults is very rare and almost always malignant. In this age group, the presence of ONGs usually reflects a bad prognosis [5]. In this case, due to the absence of progression and stable visual function, conservative management with monitoring seems encouraging in similar cases. ONGs were first described by Hoyt et al. in 1973, using data from a total of 15 adult cases with malignant optic glioma [6]. Further studies, one among them by Lin et al., reported that 70% of patients with ONGs are below 50 years of age, particularly in low-grade (LG) tumors [1]. In contrast, high-grade ONGs are usually seen in higher-aged patients, approximately around 57 and 66 years [1].

The clinical presentation of an ONG is mainly dependent on its anatomical site. There are generally some common symptoms that manifest slowly including unilateral visual deterioration, proptosis, and color vision deficiency [4]. In addition, approximately one-third of adults diagnosed with malignant ONG have headaches, eye pain, hemiplegia, and dementia [7]. In the case presented, our patient demonstrated a relatively benign clinical course. Nevertheless, although infrequent, LG ONGs in adults can sometimes manifest with malignant clinical features. Take for instance Gorkem Bilgin et al. [8] identified three adult cases of LG ONGs, all with extremely rapid progression of vision loss over months.

In most cases, the appearance of gliomas is easily identifiable on MRI scans. On T1-weighted images, these tumors generally have mild T1 prolonged relaxation times and appear iso- or mildly hyperintense when compared with the normal optic nerve. On the other hand, the T2-weighted sequences often show a hyperintense lesion with extended T2 relaxation times [4]. On contrast-enhanced computerized tomography scans, LG gliomas generally appear as a heterogenous hypo-attenuating region, which may or may not enhance. There may also be a mass effect on the surrounding structures [4]. Most of the time no biopsy is required for diagnosis and it will usually be diagnosed based on imaging and clinical examination. Nevertheless, with the advent of new molecularly targeted treatments, we see a rise in the importance and potential utility of genetic testing for this neoplasm [5]. According to the imaging features, the differential diagnosis for optic nerve lesions should be considered as meningiomas, orbital lymphoma, and other epithelial tumors or inflammatory and extraocular metastatic-related possibilities [1].

The management of ONGs is typically conducted by a multidisciplinary healthcare team. Observation is often the first step approach until significant visual impairment or radiographic progression [3]. Systemic chemotherapy is most frequently used as first-line treatment for pediatric patients due to the progressive nature of the disease or compromised vision [3]. Radiotherapy is generally indicated in patients with progressive disease despite chemotherapy, cases with intracranial extension, or with residual disease after surgery [3]. Surgical intervention is generally reserved for select cases, typically when there is progressive vision loss, significant proptosis, painful keratopathy, or compressive tumors of the optic chiasm [1].

Gliomas generally exhibit slow growth but can be infiltrating. For most patients, their vision stabilizes when tumor growth is slow. However, approximately 40% of patients will still progress [2]. The stability of the lesion in this case, documented during follow-up without aggressive intervention, highlights the potential for a conservative approach in select patients with ONGs, when there is no clear evidence of impending progression. However continuous monitoring is necessary given the unpredictable nature of ONG.

Conclusion     

While ONG in adults is usually aggressive and has a poor prognosis, in some patients the tumor may progress slowly, allowing for conservative management. However, regular monitoring is necessary even when the initial presentation and follow-up suggest that they are stable.

Competing interests     

The authors declare no competing interests.

Authors' contributions     

Hassan Moutei led the conceptualization, supervised patient care, coordinated data collection, and drafted the manuscript. Managed journal submissions and correspondence. Meryem Benmoussa conducted patient examinations, gathered diagnostic data, and contributed to the literature review and manuscript writing, particularly in the diagnostic and treatment sections. Ahmed Bennis provided expertise in interpreting radiology data and reviewed the MRI findings in the manuscript, ensuring their accurate presentation. Fouad Chraibi participated in patient follow-up and data collection, assisting with revisions, particularly on clinical outcomes and management. Meriem Abdellaoui conducted literature research and helped write the introduction and discussion, focusing on the scientific accuracy of the case context. Idriss Benatiya contributed to the diagnosis and patient management and provided feedback on the manuscript, emphasizing the case´s clinical relevance. All the authors have read and agreed to the final manuscript.

Acknowledgments     

I would like to express my sincere gratitude to the Chair of the Department of Ophthalmology for their unwavering support and leadership throughout this project. Their guidance, insights, and encouragement were instrumental in the successful completion of this work.

Figures     

Figure 1: proptosis and limitation in movement of the right eye in elevation and abduction

Figure 2: A, B) magnetic resonance imaging revealed a large fusiform lesion along the optic nerve, characterized by isointensity on T1-weighted images and hyperintensity on T2-weighted images; C, D) automated perimetry identified a visual field defect in the right eye

Figure 3: A, B) magnetic resonance imaging revealed no lesion progression at the six-month follow-up

References