Optic nerve glioma (or optic glioma), a form of glioma which affects the optic nerve, is often one of the central nervous system manifestations of Neurofibromatosis 1.

Optic gliomas are usually pilocytic tumors, and can involve the optic nerve or optic chiasm. Optic gliomas are usually associated with neurofibromatosis type 1 in 30% of patients.

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.

The most common symptom of ONSM is a gradual loss of vision in one eye. In a minority of patients this may be intermittent, at least to begin with. Less common symptoms include pain in the affected eye, protrusion of the eye, or double vision.

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.

Patients who have malignant gliomas of the optic nerve have rapidly progressive, painful visual loss accompanied by signs of an optic neuropathy. Initial visual loss may be unilateral or bilateral (chiasmal involvement), but rapid progression to bilateral blindness and death are constant features. Depending on the initial location of the tumor, visual loss may be accompanied by exophthalmos, extraocular motility

Optic nerve melanocytoma does not usually produce symptoms or grow. If they slowly grow, optic nerve melanocytoma can produce afferent pupillary defects (30%), subretinal fluid (10%), and an enlarged blind spot (75%).

On fundoscopic exam, the optic disc may be swollen, atrophic, or even normal. Central retinal vein occlusion may occur.

If the tumor is next to the optic nerve, growth can compress the nerve and cause gradual loss of vision and unilateral proptosis. Dyschromatopsia may occur. Growth can also cause compressive vascular problems like central retinal vein occlusion. Lastly, growth also causes the tumor to exceed its blood supply. In these cases, necrotic areas form inside the tumor. Necrosis can (in turn) cause intraocular and rarely orbital inflammation.

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

- Nerve sheath tumor

- Brain tumor

- Arachnoid cyst

- Optic nerve glioma

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

Children affected by pilocytic astrocytoma can present with different symptoms that might include failure to thrive (lack of appropriate weight gain/ weight loss), headache, nausea, vomiting, irritability, torticollis (tilt neck or wry neck) difficulty to coordinate movements and visual complaints (including nystagmus). The complaints may vary depending on the location and size of the neoplasm. The most common symptoms are associated with increased intracranial pressure due to the size of the neoplasm.

Symptoms of gliomas depend on which part of the central nervous system is affected. A brain glioma can cause headaches, vomiting, seizures, and cranial nerve disorders as a result of increased intracranial pressure. A glioma of the optic nerve can cause visual loss. Spinal cord gliomas can cause pain, weakness, or numbness in the extremities. Gliomas do not metastasize by the bloodstream, but they can spread via the cerebrospinal fluid and cause "drop metastases" to the spinal cord.

A child who has a subacute disorder of the central nervous system that produces cranial nerve abnormalities (especially of cranial nerve VII and the lower bulbar nerves), long-tract signs, unsteady gait secondary to spasticity, and some behavioral changes is most likely to have a pontine glioma.

Gliomas can be classified according to whether they are above or below a membrane in the brain called the tentorium. The tentorium separates the cerebrum (above) from the cerebellum (below).

- The supratentorial is above the tentorium, in the cerebrum, and mostly found in adults (70%).

- The infratentorial is below the tentorium, in the cerebellum, and mostly found in children (70%).

- The pontine tumors are located in the pons of the brainstem. The brainstem has three parts (pons, midbrain, and medulla); the pons controls critical functions such as breathing, making surgery on these extremely dangerous.

It may affect any part of the brain or even the spinal cord, optic nerve and compact white matter. Clinical manifestations are indefinite, and include headache, seizures, visual disturbances, corticospinal tract deficits, lethargy, and dementia. A case of gliomatosis cerebri presenting as rapidly progressive dementia and Parkinson's disease like symptoms has been described in an 82-year-old woman.

Signs and symptoms are mainly due to secondary increased intracranial pressure due to blockage of the fourth ventricle and are usually present for 1 to 5 months before diagnosis is made. The child typically becomes listless, with repeated episodes of vomiting, and a morning headache, which may lead to a misdiagnosis of gastrointestinal disease or migraine. Soon after, the child will develop a stumbling gait, truncal ataxia, frequent falls, diplopia, papilledema, and sixth cranial nerve palsy. Positional dizziness and nystagmus are also frequent, and facial sensory loss or motor weakness may be present. Decerebrate attacks appear late in the disease.

Extraneural metastasis to the rest of the body is rare, and when it occurs, it is in the setting of relapse, more commonly in the era prior to routine chemotherapy.

Seizures, frequent mood changes, and headaches are among the earliest symptoms of the tumor. Hemiparesis, or physical weakness on one side of the body, is also common. A continuous EEG recording of the brain's electrical activity may help to identify and localize seizure activity, especially in children. CT scans and MRI scans of the brain may show the presence of a diffuse mass that fails to light up when a contrast dye is given. In some cases, a biopsy may be required to confirm the nature of the tumour.

Pilocytic astrocytoma or juvenile pilocytic astrocytoma or cystic cerebellar astrocytoma (and its variant juvenile pilomyxoid astrocytoma) is a brain tumor that occurs more often in children and young adults (in the first 20 years of life). They usually arise in the cerebellum, near the brainstem, in the hypothalamic region, or the optic chiasm, but they may occur in any area where astrocytes are present, including the cerebral hemispheres and the spinal cord. These tumors are usually slow growing and benign. The neoplasms are associated with the formation of a single (or multiple) cyst(s), and can become very large.

Pilocytic astrocytomas are often cystic, and, if solid, tend to be well-circumscribed. It is characteristically easily seen on Computed tomography (CT scans) and Magnetic Resonance Imaging (MRI).

Juvenile pilocytic astrocytoma is associated with neurofibromatosis type 1 (NF1), and optic gliomas are among the most frequently encountered tumors in patients with this disorder. The majority of pilocytic astrocytomas have a unique KIAA1549-BRAF fusion gene.

Initial presenting symptoms most commonly are headache, depressed mental status, focal neurological deficits, and/or seizures. The growth rate and mean interval between onset of symptoms and diagnosis is approximately 1.5–2 years but is highly variable, being intermediate between that of low-grade astrocytomas and glioblastomas. Seizures are less common among patients with anaplastic astrocytomas compared to low-grade lesions.

Vision deficit usually occurs when lesions grow in the occipital lobe of the brain, causing a blurred daze for patients, especially in sensitivity to light. Focusing upon finer objects becomes a challenge, along with edge and border detection. Driving behind the wheel is dangerous when astroblastoma grows in residual tissue size, since peripheral vision can be insufficient. Horizontal nystagmus and other involuntary eye disorders can occur.

Its presence is associated with either pilocytic astrocytoma (more common) or Alexander's disease (a rare leukodystrophy). They are also seen in the context of fucosidosis.

Pilocytic astrocytoma is the most common primitive tumor in pediatric patients.

Gliomatosis cerebri (infiltrative diffuse astrocytosis) is a rare primary brain tumor. It is commonly characterized by diffuse infiltration of the brain with neoplastic glial cells that affect various areas of the cerebral lobes. These malignancies consist of infiltrative threads that spread quickly and deeply into the surrounding brain tissue, or into multiple parts of the brain simultaneously, making them very difficult to remove with surgery or treat with radiation. Gliomatosis cerebi behaves like a malignant tumor that is very similar to Glioblastoma.

While gliomatosis cerebri can occur at any age, it is generally found in the third and fourth decades of life.

Along with cranial pressure, patients exhibit noticeable lethargy, increasing in severity as the tumor progresses. In the first few months, morning activities are usually unaffected; over time, these effects become more pronounced, especially late at night. Lethargy can disrupt vital signs, depleting energy and desire to perform simple cognitive tasks.

Headaches as a result of raised intracranial pressure can be an early symptom of brain cancer. However, isolated headache without other symptoms is rarer, and other symptoms often occur before headaches become common. Certain warning signs for headache exist which make it more likely to be associated with brain cancer. These are as defined by the American Academy of Neurology: "abnormal neurological examination, headache worsened by Valsalva maneuver, headache causing awakening from sleep, new headache in the older population, progressively worsening headache, atypical headache features, or patients who do not fulfill the strict definition of migraine".

Fibrillary astrocytomas arise from neoplastic astrocytes, a type of glial cell found in the central nervous system. They may occur anywhere in the brain, or even in the spinal cord, but are most commonly found in the cerebral hemispheres. As the alternative name of "diffuse astrocytoma" implies, the outline of the tumour is not clearly visible in scans, because the borders of the neoplasm tend to send out tiny microscopic fibrillary tentacles that spread into the surrounding brain tissue. These tentacles intermingle with healthy brain cells, making complete surgical removal difficult. However, they are low grade tumors, with a slow rate of growth, so that patients commonly survive longer than those with otherwise similar types of brain tumour, such as glioblastoma multiforme.

A Rosenthal fiber is a thick, elongated, worm-like or "corkscrew" eosinophilic (pink) bundle that is found on H&E staining of the brain in the presence of long-standing gliosis, occasional tumors, and some metabolic disorders.

The signs and symptoms of brain tumors are broad. People with brain tumors will experience them no matter if the tumor is benign (not cancerous) or cancerous. Primary and secondary brain tumors present with similar symptoms, depending on the location, size, and rate of growth of the tumor. For example, larger tumors in the frontal lobe can cause changes in the ability to think. However, a smaller tumor in an area such as Wernicke's area (small area responsible for language comprehension) can result in a greater loss of function.

Ganglioglioma is a rare, slow-growing primary central nervous system (CNS) tumor which most frequently occurs in the temporal lobes of children and young adults.

Astrocytomas are a type of cancer of the brain. They originate in a particular kind of glial cells, star-shaped brain cells in the cerebrum called astrocytes. This type of tumor does not usually spread outside the brain and spinal cord and it does not usually affect other organs. Astrocytomas are the most common glioma and can occur in most parts of the brain and occasionally in the spinal cord. Within the astrocytomas, there are two broad classes recognized in literature, those with:

- Narrow zones of infiltration (mostly noninvasive tumors; e.g., pilocytic astrocytoma, subependymal giant cell astrocytoma, pleomorphic xanthoastrocytoma), that often are clearly outlined on diagnostic images

- Diffuse zones of infiltration (e.g., high-grade astrocytoma, anaplastic astrocytoma, glioblastoma), that share various features, including the ability to arise at any location in the CNS (Central Nervous System), but with a preference for the cerebral hemispheres; they occur usually in adults; and an intrinsic tendency to progress to more advanced grades.

People can develop astrocytomas at any age. The low-grade type is more often found in children or young adults, while the high-grade type are more prevalent in adults. Astrocytomas in the base of the brain are more common in young people and account for roughly 75% of neuroepithelial tumors.