Neurofibromatosis is diagnosed from a combination of findings. For children to be diagnosed with NF1, they must show at least two of the aforementioned symptoms associated with NF1. A physical examination by a doctor familiar with the disorder is usually performed. Doctors may use special lamps to examine the skin for café-au-lait spots. Doctors may also rely on magnetic resonance imaging (MRI), X-rays, computerized tomography (CT scan) and blood tests to detect defects in the NF1 gene.
For NF2, doctors will pay close attention to hearing loss. Hearing tests as well as imaging tests are used to look for tumors in and around the auditory nerves, the spinal cord or the brain. Audiometry and brainstem auditory evoked response tests can help determine whether the eighth cranial nerve is functioning properly. Family history of NF2 is also a key focal area for diagnosis.
Genetic testing is also used to diagnose NF1 and NF2. Testing conducted before birth (prenatal) is helpful to identify individuals who have a family history of the disorder, but do not yet have the symptoms. Still, gene tests have no way of predicting the severity of NF1 or NF2. Genetic testing is performed by either direct gene mutation analysis and/or linkage analysis. Mutation analysis looks to identify the particular gene changes that cause NF. A linkage analysis is useful if the mutation analysis does not provide enough conclusive information. With at linkage analysis, blood tests from multiple family members are taken to track the chromosome that carry the disease-causing gene through two or more generations. Linkage testing is around 90 percent accurate in determining whether individuals have NF. Mutation analysis is 95 percent accurate in finding a mutation for NF1, and 65 percent accurate for NF2.