Patients with clinically confirmed neurofibromatosis type 1 (NF1) or neurofibromatosis type 2 (NF2) or a known neurofibromatosis (NF) mutation aged 5 years and above will be eligible to participate and will be recruited from the neurofibromatosis clinic. Given the need for identifying measures that can reliably and sensitively measure focal muscle weakness and allow for measuring muscle strength as a functional outcome in therapeutic clinical trials in NF, this pilot study will assess the reliability of measuring muscle strength in NF1 and NF2 using a hand-held dynamometer.

Inclusion Criteria:

• For cohort 1:

  • Patients must have clinically confirmed NF1 using the NIH consensus criteria or a known NF1 mutation
  • Ages 5 years and above
  • < 5/5 strength on Manual Muscle Testing (MMT) testing in at least one muscle group tested on the day of enrollment
  • Able to follow instructions and cooperate with exam to assess strength

• For Cohort 2

  • Patients must have clinically (NIH or Manchester criteria) or genetically confirmed diagnosis of NF2
  • Ages 5 years and above
  • < 5/5 strength on MMT testing in at least one muscle group tested on the day of enrollment
  • Able to follow instructions and cooperate with exam to assess strength

Exclusion Criteria:

• No orthopedic procedure or other major surgery that could influence extremity strength in past 6 months
• No tibial dysplasia

De-identified data for patients who consent for their data to be shared for future research.

The data will be made available: Requests should be directed to xxx@yyy. To gain access, data requestors will need to sign a data access agreement.

Beginning 3 months and ending 5 years following article publication

Investigators whose proposed use of the data has been approved by an independent review committee ("learned intermediary") identified for this purpose will have access to the data.