About 1–2% of all meningiomas are optic nerve sheath meningiomas. Meningiomas have an incidence of ~4.18/100,000 persons each year. Thus, ~10,000 meningiomas are diagnosed in the US each year; corresponding to ~100 cases of ONSM each year in the US. The actual number of meningiomas is likely much higher as it is very common in elderly women. ONSM comprises about 2% of orbital tumors, and about 10% of optic nerve lesions.

Neurofibromatosis type II (NF-2) affects around 9% of ONSM patients, where the incidence in the general population is around 0.03–0.05%. Thus NF-2 is felt to be a risk factor for the development of ONSM.

Optic gliomas often have a shifting clinical course, with sporadic periods of vision loss separated by long periods of visual stability. Optic gliomas rarely spontaneously regress.

Optic nerve sheath meningiomas (ONSM) are rare benign tumors of the optic nerve. 60–70% of cases occur in middle age females, and is more common in older adults (mean age 44.7 years). It is also seen in children, but this is rare. The tumors grow from cells that surround the optic nerve, and as the tumor grows, it compresses the optic nerve. This causes loss of vision in the affected eye. Rarely, it may affect both eyes at the same time.

It is typically a slow growing tumor, and has never been reported to cause death. However, there is concern that the tumor can grow into the brain and cause other types of neurological damage. In some patients, the tumor grows so slowly that treatment is not necessary. Standard treatments are observation, surgery, radiation therapy, and combinations of the above.

In most cases, the cause of acoustic neuromas is unknown. The only statistically significant risk factor for developing an acoustic neuroma is having a rare genetic condition called neurofibromatosis type 2 (NF2). There are no confirmed environmental risk factors for acoustic neuroma. There are conflicting studies on the association between acoustic neuromas and cellular phone use and repeated exposure to loud noise. In 2011, an arm of the World Health Organization released a statement listing cell phone use as a low grade cancer risk. The Acoustic Neuroma Association recommends that cell phone users use a hands-free device.

Meningiomas are significantly more common in women than in men; they are most common in middle-aged women. Two predisposing factors associated with meningiomas for which at least some evidence exists are exposure to ionizing radiation (cancer treatment of brain tumors) and hormone replacement therapy.

While radiation or chemotherapy may be helpful, treatment is often not necessary. Optical gliomas often cannot be surgically resected. If no visual symptoms wait 6 months and then in 6 months only treat if there are symptoms (visual loss, eye pain), otherwise do not treat.

Most optic nerve melanocytomas are small, black, and do not grow.

Most optic nerve tumors (65 percent) are gliomas that occur somewhere along the anterior visual pathway.

Foroozen divides the causes of chiasmal syndromes into intrinsic and extrinsic causes. Intrinsic implies thickening of the chiasm itself and extrinsic implies compression by another structure. Other less common causes of chiasmal syndrome are metabolic, toxic, traumatic or infectious in nature.

Intrinsic etiologies include gliomas and multiple sclerosis. Gliomas of the optic chiasm are usually derived from astrocytes. These tumors are slow growing and more often found children. However, they have a worse prognosis, especially if they have extended into the hypothalamus. They are frequently associated with neurofibromatosis type 1 (NF-1). Their treatment involves the resection of the optic nerve. The supposed artifactual nature of Wilbrand's knee has implications for the degree of resection that can be obtained, namely by cutting the optic nerve immediately at the junction with the chiasm without fear of potentially resulting visual field deficits.

The vast majority of chiasmal syndromes are compressive. Ruben et al. describe several compressive etiologies, which are important to understand if they are to be successfully managed. The usual suspects are pituitary adenomas, craniopharyngiomas, and meningiomas.

Pituitary tumors are the most common cause of chiasmal syndromes. Visual field defects may be one of the first signs of non-functional pituitary tumor. These are much less frequent than functional adenomas. Systemic hormonal aberrations such as Cushing’s syndrome, galactorrhea and acromegaly usually predate the compressive signs. Pituitary tumors often encroach upon the middle chiasm from below. Pituitary apoplexy is one of the few acute chiasmal syndromes. It can lead to sudden visual loss as the hemorrhagic adenoma rapidly enlarges.

The embryonic remnants of Rathke’s pouch may undergo neoplastic change called a craniopharyngioma. These tumors may develop at any time but two age groups are most at risk. One peak occurs during the first twenty years of life and the other occurs between fifty and seventy years of age. Craniopharyngiomas generally approach the optic chiasm from behind and above. Extension of craniopharyngiomas into the third ventricle may cause hydrocephalus.

Meningiomas can develop from the arachnoid layer. Tuberculum sellae and sphenoid planum meningiomas usually compress the optic chiasm from below. If the meningioma arises from the diaphragma sellae the posterior chiasm is damaged. Medial sphenoid ridge types can push on the chiasm from the side. Olfactory groove subfrontal types can reach the chiasm from above. Meningiomas are also associated with neurofibromatosis type 1. Women are more prone to develop meningiomas.

Because hearing loss in those with NF-2 almost always occurs after acquisition of verbal language skills, patients do not always integrate well into the Deaf culture and are more likely to resort to auditory assistive technology.

The most sophisticated of these devices is the cochlear implant, which can sometimes restore a high level of auditory function even when natural hearing is totally lost. However, the amount of destruction to the cochlear nerve caused by the typical NF2 schwannoma often precludes the use of such an implant. In these cases, an auditory brainstem implant (ABI) can restore a primitive level of hearing, which, when supplemented by lip reading, can restore a functional understanding of spoken language.

The clinical spectrum of the condition is broad. In other words, people with NF II may develop a wide range of distinct problems.

1. Acoustic nerve: 90% of the patients show bilateral acoustic schwannomas on magnetic resonance imaging (MRI).

2. Other cranial nerves and meninges: About 50% of patients develop tumours in other cranial nerves or meningiomas.

3. Spinal cord: About 50% of the patients develop spinal lesions. Only 40% of the spinal lesions are symptomatic. The spinal tumours in NF II are separated in two groups. Intramedullary lesions are located within the spinal tissue and usually belong to the so-called spinal astrocytomas or ependymomas. The extramedullary lesions are located within the small space between the surface of the spinal cord and the bony wall of the spinal canal. These tumours belong to the schwannomas and meningiomas.

4. Skin: If children show neurofibromas, a diagnostic procedure should be performed to decide which form of neurofibromatosis causes the alterations.

5. Eyes: Studies on patients with NF II show that more than 90% of the affected persons suffer eye lesions. The most common alteration in NF II is the juvenile subcapsular cataract (opacity of the lens) in young people.

"Presenting symptoms" (initial concern that brings a patient to a doctor) of a lesion of the nervus vestibulocochlearis due to a tumour in the region of the cerebello-pontine angle are the following: hearing loss (98%), tinnitus (70%), dysequilibrium (67%), headache (32%), facial numbness and weakness (29% and 10% respectively).

"Clinical signs" (alterations that are not regarded by the patient and that can be detected by the doctor in a clinical examination) of the lesion in discussion are: abnormal corneal reflex (33%), nystagmus (26%), facial hypesthesia (26%).

Evaluation (study of the patient with technical methods) shows the enlargement of the porus acousticus internus in the CT scan, enhancing tumours in the region of the cerebello-pontine angle in gadolinium-enhanced MRI scans, hearing loss in audiometric studies and perhaps pathological findings in electronystagmography. Some times there are elevated levels of protein in liquor study.

In NF II, acoustic neuromas usually affect young people, whereas in sporadic forms of acoustic neuromas, the appearance of the tumour is limited to the elderly.

There are two forms of the NF II:

- The "Wishart-Phenotype" is characterized by multiple cerebral and spinal lesions in patients younger than 20 years and with rapid progression of the tumours.

- Patients that develop single central tumours with slow progression after age of 20 are thought to have the "Feiling-Gardner-Phenotype".

The overall complication rate following surgery is around 20%; cerebrospinal fluid leak is the most common.

The causes of meningiomas are not well understood. Most cases are sporadic, appearing randomly, while some are familial. Persons who have undergone radiation, especially to the scalp, are more at risk for developing meningiomas, as are those who have had a brain injury. Atomic bomb survivors from Hiroshima had a higher than typical frequency of developing meningiomas, with the incidence increasing the closer that they were to the site of the explosion. Dental x-rays are correlated with an increased risk of meningioma, in particular for people who had frequent dental x-rays in the past, when the x-ray dose of a dental x-ray was higher than in the present.

Having excess body fat increases the risk.

A 2012 review found that mobile telephone use was unrelated to meningioma.

People with neurofibromatosis type 2 (NF-2) have a 50% chance of developing one or more meningiomas.

Ninety-two percent of meningiomas are benign. Eight percent are either atypical or malignant.

Many individuals have meningiomas, but remain asymptomatic, so the meningiomas are discovered during an autopsy. One to two percent of all autopsies reveal meningiomas that were unknown to the individuals during their lifetime, since there were never any symptoms. In the 1970s, tumors causing symptoms were discovered in 2 out of 100,000 people, while tumors discovered without causing symptoms occurred in 5.7 out of 100,000, for a total incidence of 7.7/100,000. With the advent of modern sophisticated imaging systems such as CT scans, the discovery of asymptomatic meningiomas has tripled.

Meningiomas are more likely to appear in women than men, though when they appear in men, they are more likely to be malignant. Meningiomas may appear at any age, but most commonly are noticed in men and women age 50 or older, with meningiomas becoming more likely with age. They have been observed in all cultures, Western and Eastern, in roughly the same statistical frequency as other possible brain tumors.

Although many perinatal and prenatal risk factors for ONH have been suggested, the predominant, enduring, most frequent risk factors are young maternal age and primiparity (the affected child being the first child born to the mother). Increased frequency of delivery by caesarean section and fetal/neonatal complications, preterm labor, gestational vaginal bleeding, low maternal weight gain, and weight loss during pregnancy are also associated with ONH.

Chiasmal syndrome is the set of signs and symptoms that are associated with lesions of the optic chiasm, manifesting as various impairments of the sufferer's visual field according to the location of the lesion along the optic nerve. Pituitary adenomas are the most common cause; however, chiasmal syndrome may be caused by cancer, or associated with other medical conditions such as multiple sclerosis and neurofibromatosis.

A schwannoma is a usually-benign nerve sheath tumor composed of Schwann cells, which normally produce the insulating myelin sheath covering peripheral nerves.

A nerve sheath tumor is a type of tumor of the nervous system (nervous system neoplasm) which is made up primarily of the myelin surrounding nerves.

A peripheral nerve sheath tumor (PNST) is a nerve sheath tumor in the peripheral nervous system. Benign peripheral nerve sheath tumors include schwannomas and neurofibromas.

A malignant peripheral nerve sheath tumor (MPNST) is a cancerous peripheral nerve sheath tumor.

Optic pits occur equally between men and women. They are seen in roughly 1 in 10,000 eyes, and approximately 85% of optic pits are found to be unilateral (i.e. in only one eye of any affected individual). About 70% are found on the temporal side (or lateral one-half) of the optic disc. Another 20% are found centrally, while the remaining pits are located either superiorly (in the upper one-half), inferiorly (in the lower one-half), or nasally (in the medial one-half towards the nose).

Mutations of genes involved in transcription regulation, chromatin remodelling, α-dystroglycan glycosylation, cytoskeleton and scaffolding protein, RNA splicing, and the MAP kinase signalling pathway are currently known to cause ONH. Many transcription factors for eye development are also involved in the morphogenesis of forebrain, which may explain why ONH is commonly a part of a syndrome involving brain malformations.

ONH impacts all ethnic groups, although in the United States, occurrence is lower in persons of Asian descent. To date, there have been few reports of ONH occurrence in Asian countries, although it is uncertain why this is so.

Optic disc drusen are found clinically in about 1% of the population but this increases to 3.4% in individuals with a family history of ODD. About two thirds to three quarters of clinical cases are bilateral. A necropsy study of 737 cases showed a 2.4% incidence with 2 out of 15 (13%) bilateral, perhaps indicating the insidious nature of many cases. An autosomal dominant inheritance pattern with incomplete penetrance and associated inherited dysplasia of the optic disc and its blood supply is suspected. Males and females are affected at equal rates. Caucasians are the most susceptible ethnic group. Certain conditions have been associated with disc drusen such as retinitis pigmentosa, angioid streaks, Usher syndrome, Noonan syndrome and Alagille syndrome. Optic disc drusen are not related to Bruch membrane drusen of the retina which have been associated with age-related macular degeneration.

Toxic optic neuropathy refers to the ingestion of a toxin or an adverse drug reaction that results in vision loss from optic nerve damage. Patients may report either a sudden loss of vision in both eyes, in the setting of an acute intoxication, or an insidious asymmetric loss of vision from an adverse drug reaction. The most important aspect of treatment is recognition and drug withdrawal.

Among the many causes of TON, the top 10 toxins include:

- Medications

- Ethambutol, rifampin, isoniazid, streptomycin (tuberculosis treatment)

- Linezolid (taken for bacterial infections, including pneumonia)

- Chloramphenicol (taken for serious infections not helped by other antibiotics)

- Isoretinoin (taken for severe acne that fails to respond to other treatments)

- Ciclosporin (widely used immunosuppressant)

- Acute Toxins

- Methanol (component of some moonshine, and some cleaning products)

- Ethylene glycol (present in anti-freeze and hydraulic brake fluid)

Metabolic disorders may also cause this version of disease. Systemic problems such as diabetes mellitus, kidney failure, and thyroid disease can cause optic neuropathy, which is likely through buildup of toxic substances within the body. In most cases, the cause of the toxic neuropathy impairs the tissue’s vascular supply or metabolism. It remains unknown as to why certain agents are toxic to the optic nerve while others are not and why particularly the papillomacular bundle gets affected.

A nervous system neoplasm is a tumor affecting the nervous system. Types include:

- Nerve sheath tumor

- Brain tumor

- Arachnoid cyst

- Optic nerve glioma

No particular risk factors have been conclusively identified; however, there have been a few reports that demonstrate an autosomal dominant pattern of inheritance in some families. Therefore, a family history of optic pits may be a possible risk factor.

"Idiopathic" means of unknown cause. Therefore, IIH can only be diagnosed if there is no alternative explanation for the symptoms. Intracranial pressure may be increased due to medications such as high-dose vitamin A derivatives (e.g. isotretinoin for acne), long-term tetracycline antibiotics (for a variety of skin conditions) and hormonal contraceptives. There are numerous other diseases, mostly rare conditions, that may lead to intracranial hypertension. If there is an underlying cause, the condition is termed "secondary intracranial hypertension". Common causes of secondary intracranial hypertension include obstructive sleep apnea (a sleep-related breathing disorder), systemic lupus erythematosus (SLE), chronic kidney disease, and Behçet's disease.

Optic neuritis typically affects young adults ranging from 18–45 years of age, with a mean age of 30–35 years. There is a strong female predominance. The annual incidence is approximately 5/100,000, with a prevalence estimated to be 115/100,000.