Diagnosing Neurofibromatosis

To diagnose any of the three types of neurofibromatosis—neurofibromatosis type 1, neurofibromatosis type 2, or schwannomatosis—our doctors conduct a physical exam, take a medical history, and may perform imaging tests and genetic tests. Children receive diagnosis and treatment of neurofibromatosis through Hassenfeld Children’s Hospital at NYU Langone.

Diagnosing Neurofibromatosis Type 1

Neurofibromatosis type 1 can usually be identified with a physical exam, in which your doctor looks for signs of the condition such as light-brown café-au-lait spots or tumors on the skin. Although café-au-lait spots are often present at birth, some of the physical features of the condition are not obvious until a child is older than five years. About 97 percent of those with neurofibromatosis type 1 have enough features of the disorder to make the diagnosis by the time a child is eight years old.

The National Institutes of Health have developed guidelines for diagnosing neurofibromatosis type 1. According to these criteria, the condition is present when a person has two or more of the following signs:

• six or more café-au-lait spots larger than 5 mm across before puberty and larger than 15 mm across after puberty
• two or more neurofibromas of any type or one plexiform neurofibroma
• freckling of the skin in the underarm or groin areas
• a tumor of the optic pathway, meaning the nerves that run between the eyes and the brain
• two or more Lisch nodules, which are small growths that appear as bumps on the iris, the colored portion of the eye
• a distinctive bone malformation, such as sphenoid wing dysplasia in one of the bones behind the eye, or thinning of the long bones in the arms of legs (children may also have pseudarthrosis, meaning a false joint that can occur when a bone fractures and does not heal properly)
• a first-degree relative, meaning a parent, sibling, son, or daughter, who also meets these criteria

Diagnosing Neurofibromatosis Type 2

Many people with neurofibromatosis type 2 first see a doctor because of hearing loss, ringing in the ears, balance problems, or facial weakness. These symptoms are usually caused by eighth cranial nerve tumors, also called vestibular schwannomas or acoustic neuromas.

After an initial physical exam, doctors may order an MRI scan, which uses a powerful magnetic field and radio waves to produce detailed pictures of the brain and spinal cord.

Doctors usually make a diagnosis of neurofibromatosis type 2 if an MRI scan reveals bilateral vestibular schwannomas. This means that vestibular schwannomas are present on both the right and left eighth cranial nerves, the nerves that run between the ears and the brain stem on either side of the head.

Neurofibromatosis type 2 may also be diagnosed if a first-degree relative, meaning a parent, sibling, son, or daughter, has the condition, and if a one-sided, or unilateral, vestibular schwannoma is present or if other growths associated with the condition have developed.

These other growths can include schwannoma, meaning a nerve-sheath tumor arising from Schwann cells; meningioma, which is a tumor arising from the linings of the brain and spinal cord; or a rare form of cataract or clouding of the eye called subcapsular lenticular opacities.

Doctors may also make a diagnosis of neurofibromatosis type 2 if a one-sided, or unilateral, vestibular schwannoma and other characteristic lesions are present, such as meningioma, schwannoma, or subcapsular lenticular opacities.

Diagnosing Schwannomatosis

NYU Langone doctors perform diagnostic tests for schwannomatosis when a person has multiple schwannomas, or painful, distinct lumps in the skin or muscle, whether or not he or she has a family member with the condition.

Doctors usually need to surgically remove at least one tumor for examination under a microscope, also called a biopsy, in order to confirm the diagnosis.

Additionally, doctors need to exclude a diagnosis of neurofibromatosis type 2. To do this, they look for tumors associated with the condition, such as vestibular schwannomas on the eight cranial nerves.

An initial evaluation may include taking a detailed clinical and family history and reviewing available tumor pathology, meaning the information gathered by looking at a growth under a microscope. Doctors may perform a high-resolution brain MRI that also looks at the internal auditory canal, which contains the eight cranial nerves.

Genetic Testing

Genetic testing is available for neurofibromatosis type 1, neurofibromatosis type 2, and schwannomatosis, under the supervision of physicians and genetic counselors at NYU Langone’s Clinical Genetic Services.

Genetic testing isn’t necessary for most people. However, if you and your doctor decide you need to confirm a diagnosis, or if you are planning to have children or want to know whether other family members have the condition or might be at risk, genetic testing is available. The costs of testing and insurance coverage are other factors to consider.

Neurofibromatosis Type 1 Genetic Testing

A blood test is available for genetic testing to see whether a mutation in the neurofibromatosis type 1 gene is present. A diagnosis of neurofibromatosis type 1 is still possible in people who don't have an identifiable mutation.

Testing can now also be performed for SPRED1. This is a gene associated with an uncommon neurofibromatosis type 1–like disorder called Legius syndrome. This syndrome causes café-au-lait spots and freckling under the arms and in the groin area, but without the neurofibromas or optic pathway gliomas typical of neurofibromatosis type 1.

Neurofibromatosis Type 2 Genetic Testing

In neurofibromatosis type 2, some mutations are known to result in milder symptoms and progression of the condition. Others are associated with more aggressive symptoms and progression.

Genetic blood testing for neurofibromatosis type 2 is accurate in more than 90 percent of people who inherited the condition from a parent. In people who are the first to develop neurofibromatosis type 2 in their family, the mutations may not be present in all of the body’s cells, and there is a chance that genetic testing of the blood may be negative. In these people, genetic testing of tumor tissue can greatly increase the likelihood of finding the neurofibromatosis type 2 mutation.

Schwannomatosis Genetic Testing

Genetic testing is not required for the diagnosis of schwannomatosis and is not suggested for most people. Aside from SMARCB1 and LZTR1, there may be other genes causing the condition that have not yet been identified, limiting the usefulness of genetic testing. Genetic testing of the schwannoma tissue with a blood sample may be more informative.