Neuroimaging, such as MRI, is the main diagnostic tool for brain stem gliomas. In very rare cases, surgery and biopsy are performed.

Visual fields associated with chiasmal syndrome usually leads to an MRI. Contrast can delineate arterial aneurysms and will enhance most intrinsic chiasmal lesions. If a mass is confirmed on MRI, an endocrine panel can help determine if a pituitary adenoma is involved.

In patients with functional adenomas diagnosed by other means, visual field tests are a good screen to test for chiasmal involvement. Visual fields tests will delinate chiasmal syndromes because the missing fields will not cross the midline. Junctional scotomas classically show ipsilateral optic disc neuropathy with contralateral superotemporal defects. Bitemporal hemianopia with or without central scotoma is present if the lesions have affected the body of the chiasm. A posterior chiasm lesion should only produce defects on the temporal sides of the central visual field.

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.

ONSM does not improve without treatment. In many cases, there is gradual progression until vision is lost in the affected eye. However, this takes at least several months to occur, and a minority of patients remain stable for a number of years.

Bilateral vestibular schwannomas are diagnostic of NF2.

NF II can be diagnosed with 65% accuracy prenatally with chorionic villus sampling or amniocentesis.

Clinical examination will show an abnormal optic disc, either swollen or atrophic. Optociliary shunt vessels may be seen; the combination of these with progressive visual loss and optic disc atrophy is known as the Hoyt-Spencer triad. Visual acuity is usually but not always reduced.

When ONSM is suspected, MRI of the brain or orbits should be performed. This will usually show characteristic findings and confirm the diagnosis.

Ferner et al. give three sets of diagnostic criteria for NF2:

1. Bilateral vestibular schwannoma (VS) or family history of NF2 plus Unilateral VS or any two of: meningioma, glioma, neurofibroma, schwannoma, posterior subcapsular lenticular opacities

2. Unilateral VS plus any two of meningioma, glioma, neurofibroma, schwannoma, posterior subcapsular lenticular opacities

3. Two or more meningioma plus unilateral VS or any two of glioma, schwannoma and cataract.

Another set of diagnostic criteria is the following:

- Detection of bilateral acoustic neuroma by imaging-procedures

- First degree relative with NF II and the occurrence of neurofibroma, meningiomas, glioma, or Schwannoma

- First degree relative with NF II and the occurrence of juvenile posterior subcapsular cataract.

The criteria have varied over time.

Brainstem glioma is an aggressive and dangerous cancer. Without treatment, the life expectancy is typically a few months from the time of diagnosis. With appropriate treatment, 37% survive more than one year, 20% survive 2 years. and 13% survive 3 years.This is not for all brainstem glioma, this statistic reflects DIPG. There are other brainstem gliomas.

Treatment typically consists of radiotherapy and steroids for palliation of symptoms. Radiotherapy may result in minimally extended survival time. Prognosis is very poor, with only 37% of treated patients surviving one year or more. Topotecan has been studied in the treatment of brainstem glioma, otherwise, chemotherapy is probably ineffective, though further study is needed.

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.

An MRI is better than a CT scan when a brainstem tumor is in the differential diagnosis.

Gliomas are rarely curable. The prognosis for patients with high-grade gliomas is generally poor, and is especially so for older patients. Of 10,000 Americans diagnosed each year with malignant gliomas, about half are alive one year after diagnosis, and 25% after two years. Those with anaplastic astrocytoma survive about three years. Glioblastoma multiforme has a worse prognosis with less than a 12-month average survival after diagnosis, though this has extended to 14 months with more recent treatments.

For low-grade tumors, the prognosis is somewhat more optimistic. Patients diagnosed with a low-grade glioma are 17 times as likely to die as matched patients in the general population.

The age-standardized 10-year relative survival rate was 47%. One study reported that low-grade oligodendroglioma patients have a median survival of 11.6 years; another reported a median survival of 16.7 years.

Diagnosis commonly occurs later in childhood and often occurs incidentally in asymptomatic patients or as a cause of visual impairment. The first symptoms are commonly found during routine vision screenings.

A number of examinations can be used to determine the extent of the syndrome and its severity. Fluorescein angiography is quite useful in diagnosing the disease, and the use of ultrasonography and optical coherence tomography (OCT) are helpful in confirming the disease. Neuro-ophthalmic examinations reveal pupillary defects (see Marcus Gunn Pupil). Funduscopic examinations, examinations of the fundus of the eye, allow detection of arteriovenous malformations. Neurological examinations can determine hemiparesis and paresthesias. Malformations in arteriovenous connections and irregular functions in the veins may be distinguished by fluorescein angiographies. Cerebral angiography examinations may expose AVMs in the cerebrum. MRIs are also used in imaging the brain and can allow visualization of the optic nerve and any possible atrophy. MRI, CT, and cerebral angiography are all useful for investigating the extent and location of any vascular lesions that are affecting the brain. This is helpful in determining the extent of the syndrome.

Diagnosis of tumefactive MS is commonly carried out using magnetic resonance imaging (MRI) and proton MR spectroscopy (H-MRS). Diagnosis is difficult as tumefactive MS may mimic the clinical and MRI characteristics of a glioma or a cerebral abscess. However, as compared to tumors and abscesses, tumefactive lesions have an open-ring enhancement as opposed to a complete ring enhancement. Even with this information, multiple imaging technologies have to be used together with biochemical tests for accurate diagnosis of tumefactive MS.

Tumefactive demyelination is distinguished from tumor by the presence of multiple lesions, absence of cortical involvement, and decrease in lesion size or detection of new lesions on serial imaging

Prenatal testing may be used to identify the existence of NF-1 in the fetus. For embryos produced via in vitro fertilisation, it is possible via preimplantation genetic diagnosis to screen for NF-1.

Chorionic villus sampling or amniocentesis can be used to detect NF-1 in the fetus.

People with NF-1 have a 50% percent chance of passing the disorder on to their kids, but people can have a child born with NF-1 when they themselves do not have it. This is caused in a spontaneous change in the genes during pregnancy.

MRI diagnosis is based on lesions that are disseminated in time and space, meaning that there are multiple episodes and consisting of more than one area. There are two kinds of MRI used in the diagnosis of tumefactive MS, T1-weighted imaging and T2-weighted imaging. Using T1-weighted imaging, the lesions are displayed with low signal intensity, meaning that the lesions appear darker than the rest of the brain. Using T2-weighted imaging, the lesions appear with high signal intensity, meaning that the lesions appear white and brighter than the rest of the brain. When T1-weighted imaging is contrast-enhanced through the addition of gadolinium, the open ring enhancement can be viewed as a white ring around the lesion. A more specific MRI, Fluid attenuation inversion recovery (FLAIR) MRI show the signal intensity of the brain. Subjects with tumefactive multiple sclerosis may see a reduction of diffusion of the white matter in the affected area of the brain.

The National Institutes of Health (NIH) has created specific criteria for the diagnosis of NF-1. Two of these seven "Cardinal Clinical Features" are required for positive diagnosis. There is practical flowchart to distinguish between NF1, NF2 and schwannomatosis.

- Six or more café-au-lait spots over 5 mm in greatest diameter in pre-pubertal individuals and over 15 mm in greatest diameter in post-pubertal individuals. Note that multiple café-au-lait spots alone are not a definitive diagnosis of NF-1 as these spots can be caused by a number of other conditions.

- Two or more neurofibromas of any type or 1 plexiform neurofibroma

- Freckling in the axillary (Crowe sign) or inguinal regions

- Optic glioma

- Two or more Lisch nodules (pigmented iris hamartomas)

- A distinctive osseous lesion such as sphenoid dysplasia, or thinning of the long bone cortex with or without pseudarthrosis.

- A first degree relative (parent, sibling, or offspring) with NF-1 by the above criteria.

A thorough history is essential and should cover family history, diet; drug/toxin exposure social history, including tobacco and alcohol use; and occupational background, with details on whether similar cases exist among coworkers. Treatment of any chronic disease such as pernicious anemia should always be elucidated.

In most cases of nutritional/toxic optic neuropathy, the diagnosis may be obtained via detailed medical history and eye examination. Additionally, supplementary neurological imaging studies, such as MRI or enhanced CT, may be performed if the cause remains unclear.

When the details of the examination and history indicate a familial history of similar ocular or systemic disease, whether or not there is evidence of toxic or nutritional causes for disease, certain genetic tests may be required. Because there are several congenital causes of mitochondrial dysfunction, the patients history, examination, and radiological studies must be examined in order to determine the specific genetic tests required. For example, 90% of cases of Leber’s Hereditary Optic Neuropathy (LHON) are associated with three common mtDNA point mutations (m.3460G>A/MT-ND1, m.11778G>A/MT-ND4, m.14484T>C/MT-ND6) while a wider range of mtDNA mutations (MT-ND1, MT-ND5, MT-ND6; http://www.mitomap.org/) have been associated with overlapping phenotypes of LHON, MELAS, and Leigh syndrome.

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.

ONH is diagnosed by ophthalmoscopic examination. Patients with ONH exhibit an optic nerve that appears smaller than normal and different in appearance from small optic nerves caused by other eye conditions such as optic (nerve) atrophy.

DM:DD ratio has proven to be a clinically useful measurement to help diagnose optic nerve hypoplasia. Where "DM" represents the distance from Disk to Macula, and "DD" represents Disc Diameter.

The mean disc diameter (DD) is (Vertical diameter of Disc+Horizontal diameter of Disc)divided by 2. The distance between the center of the disc and the macula is DM.

"Interpretation:" When the ratio of DM to DD is greater than 3, ONH is suspected, and when it is greater than 4, Optic Nerve Hypoplasia is definite.

An optic nerve melanocytoma is a tumor made up of melanocytes and melanin. These tumors are typically a benign; they can grow, but rarely transform into a malignancy. Even so, local growth can affect adjacent tissues.

Checking the eyes for signs of papilledema should be carried out whenever there is a clinical suspicion of raised intracranial pressure, and is recommended in newly onset headaches. This may be done by ophthalmoscopy or fundus photography, and possibly slit lamp examination.

MRI will help with the diagnosis of structural abnormality of the brain. Genetic testing may also be pursued.