Optical Nerve Glioma
Optical nerve, also known as the cranial nerve II transmits the visual information between the brain and retina. The transmission comprises of the visual acuity, perception of brightness and colour and, visual impulses responsible for the light reflex and the accommodation reflex. Light reflex happens when the pupils constrict when eyes are exposed to strong beam of light. Accommodation reflex is an auto response that occurs by swelling of the lens when one tries to read up close. The optical nerve passes through the optic disk of retina to the brain. In certain children, tumors appear on the optic nerve, giving rise to a rare kind of cancer – Optic nerve glioma.
Cause and Symptoms
Most of the optic nerve gliomas begin as benign growths on the optical nerves that are responsible for carrying the visual transmission between the brain and the eyes. The cause of Optic nerve Glioma is associated with genetic disorders such as Neurofibromatosis Type 1 and Type 2. Neurofibromatosis is more likely to occur in children with genetic defects. Some of the common symptoms include freckles in sensitive areas like genitals and armpits, brown spots on the skin and, elevated nodules in the iris of the eye. Children affected with the Type 2 exhibit symptoms of impaired hearing, ringing in the ears, headache and difficulty in balancing oneself.
The symptoms usually begin with benign growths that appear on the anterior of the optic nerve and, may either spread into the cranial nerves or, into the optic nerve chiasmal junction. These tumors cause a swelling in the optical nerve. Children with optic nerve gliomas suffer from a progressive visual impairment that is later followed by Proptosis. If the tumor is malignant by nature, the patient may suffer from orbital pain, bilateral vision loss and haemorrhage in the optical nerve head. Malignant gliomas are rare and, occur in adults. The prognosis is difficult and, leaves little scope for survival.
Some of the palpable symptoms in children include nausea, vomiting, loss of appetite, disturb in body’s balance, disturbance in vision, memory impairment and a delayed growing cycle.
Diagnosis and Treatment
It has been observed that about 10 percent of the gliomas erupt within the optical nerve whereas, some erupt in the chiasm and, a few in the hypothalamus. Most of the gliomas have been observed to be multi centric. Diagnostic procedures include CT scans and MRIs that reveal the enlargement of the optical nerve and, the size and shape of the tumor causing the swelling in the optical nerve. MRI scan gives a far more detailed image of the swelling and kinking of the optic nerve due to the tumor. Presence of cystic degeneration is easily spotted during the MRI scan. Considering the various repercussions that result because of an enlarged optic nerve, the diagnosis is difficult and takes a long time. Some of the symptomatic conditions other than Neurofibromatosis, associated with optic nerve glioma are:
- Hemangioma (an abnormal increase in the number of blood vessels in the endothelial cells of the skin covering scalp, face and chest)
- Lymphoma (blood cell tumors developing in the lymphatic system)
- Rhabdomyosarcoma (Tumors developing in the skeletal muscles)
- Neuroblastoma (Tumors developing in the extra cranial space of the head)
- Ewing’s Sarcoma (Malignant tumors developing in the bones such as humerus, femur and ribs)
- Fibrous Dyslapsia (An abnormal development of fibrous tissue in the bone)
- Sarcoidosis (Abnormal increase in inflammatory cells in the lymph nodes, lungs and skin)
- Meningioma (Tumorous growth in the membranous layers – meniges of central nervous system)
In many cases of optic nerve gliomas in children, treatment is skipped if there are no growth anomalies, visual impairment or, cosmetic deformity. However, if the tumor is malignant, chemotherapy are engaged to kill the cancer cells in the optic nerve. Post therapy, corticosteroids are administered to the patient to alleviate the cranial swelling. Surgical incision is performed to remove the orbital tumors from the optic chiasm, to prevent the abnormal cells from further division, after a thorough observation of the intracranial part of the optic nerve. An early diagnosis aids in assessing if the tumor has spread into the chiasm or not. If there is an increase in the intracranial pressure, an excision procedure is performed. Radiation therapy is resorted to, only if surgical means of removing the tumor are not feasible. Although radiation therapies cull cancer cells, they can cause debilitating side effects such as, retinopathy and growth retardation. Post chemo and radiation therapies, children may suffer from certain side effects such as hiccups in cognitive development and retarded growth.
Children suffering from optic nerve glioma have higher chances of leading a normal life, if the tumor is benign and non-metastatic. However, if the tumor is malignant, chemo and radiation therapies are effective in removing the tumors despite recurrence of side effects. Parents of children afflicted with optic nerve glioma are advised to attend counselling programs to understand their children’s condition. These programs also aid the children in leading a normal life despite their life altering condition. Accredited doctors such as Dr. Debraj Shome are skilled in performing oculoplastic surgeries that cover oncology too.