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.

A study by You et al. was only able to evaluate the 47 documented cases that have been made to date. According to this study, intraocular schwannomas are more prevalent in females as compared to males with a ratio of 3:1. Additionally, individuals are more likely to present with intraocular schwannomas at a younger age than with uveal melanomas, the most common intraocular tumor. According to the participants evaluated in this study, the average age of occurrence was 37 years old, however, it is important to note that the age range documented represented individuals 9–76 years old.

The cause of acoustic neuromas is usually unknown; however there is a growing body of evidence that sporadic defects in tumor suppressor genes may give rise to these tumors in some individuals. In particular, loss or mutation of a tumor suppressor gene on the long arm of chromosome 22 is strongly associated with vestibular schwannomas. Other studies have hinted at exposure to loud noise on a consistent basis. One study has shown a relationship between acoustic neuromas and prior exposure to head and neck radiation, and a concomitant history of having had a parathyroid adenoma (tumor found in proximity to the thyroid gland controlling calcium metabolism). There are even controversies on hand held cellular phones. Whether or not the radiofrequency radiation has anything to do with acoustic neuroma formation, remains to be seen. To date, no environmental factor (such as cell phones or diet) has been scientifically proven to cause these tumors. The Acoustic Neuroma Association (ANA) does recommend that frequent cellular phone users use a hands free device to enable separation of the device from the head.

Although there is an inheritable condition called Neurofibromatosis Type 2 (NF2) which can lead to acoustic neuroma formation in some people, most acoustic neuromas occur spontaneously without any evidence of family history (95%). NF2 occurs with a frequency of 1 in 30,000 to 1 in 50,000 births. The hallmark of this disorder is bilateral acoustic neuromas (an acoustic neuroma on both sides) usually developing in late childhood or early adulthood, frequently associated with other brain and spinal chord tumors.

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

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".

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.

Schwannomatosis can not presently be diagnosed prenatally or in the embryo, because the gene for it has not yet been positively identified.

In most cases, symptoms of NF1 are mild, and individuals live normal and productive lives. In some cases, however, NF1 can be severely debilitating and may cause cosmetic and psychological issues. The course of NF2 varies greatly among individuals. In some cases of NF2, the damage to nearby vital structures, such as other cranial nerves and the brain stem, can be life-threatening. Most individuals with schwannomatosis have significant pain. In some extreme cases the pain will be severe and disabling.

Large tumors may cause disabling and life-threatening symptoms.

Large tumors that compress the adjacent brainstem may affect other local cranial nerves. The glossopharyngeal and vagus nerves are uncommonly involved, but their involvement may lead to altered gag or swallowing reflexes.

Larger tumors may lead to increased intracranial pressure, with its associated symptoms such as headache, vomiting, clumsy gait and mental confusion. This can be a life-threatening complication requiring urgent treatment.

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

In reported cases of the tumor over the last 25 years, the number of affected females with astroblastoma is significantly higher than the number of affected males. Sughrue et al. confirmed this trend, stating that 70% of the cases with clearly stated gender were female (100 cases total). While several publications support a genetic predisposition to females, the underlying reasons are still unknown.

The candidate schwannomatosis gene, named SMARCB1, is a tumor suppressor gene that regulates cell cycle, growth and differentiation. An inactivating germline mutation in exon 1 of the tumor suppressor gene SMARCB1 has been reported in patients with schwannomatosis. It is located on chromosome 22 a short distance from the NF2 gene. However, molecular analysis of the NF2 gene in schwannomatosis patients has shown the presence of inactivating mutations in the tumor cells, but no evidence of the germline mutations that are found in NF2 patients.

A mechanism involving both the SMARCB1 and NF2 genes may be responsible for the development of the disease because tumor analysis of schwannomas indicates the presence of inactivating mutations in both the SMARCB1 and NF2 genes. However, there is speculation about the involvement of an unidentified schwannomatosis gene(s) in most cases. This is because one study found no SMARCB1 germinal mutations in patients with familial schwannomatosis. Some schwannomatosis patients do not have SMARCB1 or NF2 mutations. Furthermore, many patients exhibit somatic mosaicism for mutations in the NF2 or SMARCB1 gene, which means that some somatic cells have the mutation and some do not in the same patient. Ultimately, the tumorigenesis of schwannomas is not solely dependent on one gene locus alone. In regards to the SMARCB1 and NF2 genes, it is important to understand constitutional mutations and somatic mutations. Constitutional mutations are the first inactivation events that are often small mutations, such as point mutations and deletion/insertion of single base pairs. Somatic mutations are the second mutations that occur and may also be another small mutation or the loss of the remaining allele of the gene. Schwannomas from one patient share the same constitutional mutations but have distinct somatic mutations. In addition, the constitutional mutation may be present in non-tumor

SMARCB1 is also known as INI1, hSNF5, or BAF47. SMARCB1 is mutated in additional tumors including malignant brain & kidney tumors in children. It seems that heterozygotes for mutations in the SMARCB1 gene have an increased risk to develop a malignant kidney tumor in early childhood but if they survive to adulthood, they may be predisposed to the development of schwannomas. One schwannomatosis patient had a mutation in exon 2 of the SMARCB1 gene. Another patient exhibited a novel germline deletion of the SMARCB1, because most SMARCB1 mutations are point or frameshift. In this patient genetic analysis from different schwannomas indicated inactivation of both the SMARCB1 and NF2 genes. Schwannomatosis is known to be a genetic disorder. However, familial occurrence is inexplicably rare.

Schwannomas are homogeneous tumors, consisting only of Schwann cells. The tumor cells always stay on the outside of the nerve, but the tumor itself may either push the nerve aside and/or up against a bony structure (thereby possibly causing damage). Schwannomas are relatively slow-growing. For reasons not yet understood, schwannomas are mostly benign and less than 1% become malignant, degenerating into a form of cancer known as neurofibrosarcoma. These masses are generally contained within a capsule, and so surgical removal is often successful.

Schwannomas can be associated with neurofibromatosis type II, which may be due to a loss-of-function mutation in the protein merlin. They are universally S-100 positive, which is a marker for cells of neural crest cell origin.

Schwannomas of the head and neck are a fairly common occurrence and can be found incidentally in 3–4% of patients at autopsy. Most common of these is a vestibular schwannoma, a tumor of the vestibulocochlear nerve that may lead to tinnitus and hearing loss on the affected side. Outside the cranial nerves, schwannomas may present on the flexor surfaces of the limbs. Rare occurrences of these tumors in the penis have been documented in the literature.

Verocay bodies are seen histologically in schwannomas.

The systemic and ocular prognosis for intraocular schwannoma is positive. While a patient may lose an eye, they are unlikely to encounter metastasized growth or life-threatening malignant change. Although follow-up data has shown the potential need for re-excision and side-effects, these issues are minor and the general outcome for patients is excellent.

At this point, no literature has indicated whether environmental factors increase the likelihood of astroblastoma. Although cancer in general is caused by a variety of external factors, including carcinogens, dangerous chemicals, and viral infections, astroblastoma research has not even attempted to classify incidence in this regard. The next few decades will aid in this understanding.

NF1 occurs in 1 in 3000 individuals and is equally prevalent among men and women. It is among the most common inherited nervous system disorders. Affected individuals have a 10- to 15-year reduction in life expectancy compared to the average person.

Papillary tumors of pineal region are extremely rare, constituting 0.4-1% of all central nervous system tumors. These tumors most commonly occur in adults with the mean age being 31.5. There have been cases reported for people between the ages 5 to 66 years. There is a slight predominance of females who have these tumors.

Choroid plexus tumors have an annual incidence of about 0.3 per 1 million cases.

It is seen mainly in children under the age of 5, representing 5% of all pediatric tumors and 20% of tumors in children less than 1 year old. There has been no link between sex and occurrence.

Although choroid plexus carcinomas are significantly more aggressive and have half the survival rate as choroid plexus papillomas, they are outnumbered in incidence by 5:1 in all age groups. Clinical studies have shown that patients who receive a total resection of a tumor have a 86% survival rate, while patients who only receive a partial resection have a 26% 5-year survival rate. Many incomplete resections result in recurrence within 2 years of primary surgery.

Other causes may include:

- Diabetes mellitus

- Facial nerve paralysis, sometimes bilateral, is a common manifestation of sarcoidosis of the nervous system, neurosarcoidosis.

- Bilateral facial nerve paralysis may occur in Guillain–Barré syndrome, an autoimmune condition of the peripheral nervous system.

- Moebius syndrome is a bilateral facial paralysis resulting from the underdevelopment of the VII cranial nerve (facial nerve), which is present at birth. The VI cranial nerve, which controls lateral eye movement, is also affected, so people with Moebius syndrome cannot form facial expression or move their eyes from side to side. Moebius syndrome is extremely rare, and its cause or causes are not known.

The cause of choroid plexus carcinomas are relatively unknown, although hereditary factors are suspected. The sometimes occur in conjunction with other hereditary cancers, including Li–Fraumeni syndrome and malignant rhabdoid tumors. A mutation in the tumor suppressor gene TP53 is usually characterized in this disease.

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.

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.

Central facial palsy can be caused by a lacunar infarct affecting fibers in the internal capsule going to the nucleus. The facial nucleus itself can be affected by infarcts of the pontine arteries.

Medulloblastomas affect just under two people per million per year, and affect children 10 times more than adults. Medulloblastoma is the second-most frequent brain tumor in children after pilocytic astrocytoma and the most common malignant brain tumor in children, comprising 14.5% of newly diagnosed cases. In adults, medulloblastoma is rare, comprising fewer than 2% of CNS malignancies.

The rate of new cases of childhood medulloblastoma is higher in males (62%) than females (38%), a feature which is not seen in adults. Medulloblastoma and other PNET`s are more prevalent in younger children than older children. About 40% of medulloblastoma patients are diagnosed before the age of five, 31% are between the ages of 5 and 9, 18.3% are between the ages of 10 and 14, and 12.7% are between the ages of 15 and 19.

The symptoms of brain stem tumors vary greatly and can include ataxia, cranial nerve palsy, headaches, problems with speech and swallowing, hearing loss, weakness, hemiparesis, vision abnormalities, ptosis, and behavioral changes. Another possible symptom is vomiting. Headaches related to brainstem tumors may be worse shortly after waking up in the morning.