Editor—We have previously reported on a large clinical study of patients with neurofibromatosis 2 (NF2)1and described the usefulness of audiological screening in early detection of VS in NF2.2 Although DNA diagnosis is possible by linkage analysis and by detecting the NF2 family specific mutation, this is not possible in all cases. Only 40% of sporadic patients (new mutations) have an identifiable NF2 mutation3 and as 50% of NF2 patients have no family history,4 up to 30% of those at risk of NF2 will not be able to have a DNA presymptomatic test. While it is possible to calculate residual risks of NF2 from age at onset of symptoms curves,5 a more useful measure would be the level of risk reduction from a normal cranial MRI scan. A database recording information on affected subjects with NF2 was set up in Manchester in 1989. Patients were actively sought across the UK from paediatricians, neurosurgeons, ENT surgeons, geneticists, and dermatologists. We have used this database to determine the age at which MRI detects asymptomatic tumours in subjects with NF2 and the value of audiological screening. We have also created life curves for risk reduction in subjects at 50% risk of NF2.

Patient details from hospital notes and proformas have been entered into a database at St Mary's Hospital Manchester since 1989. A total of 344 patients fulfilling our published criteria for NF2 are recorded (table 1).1 3 5 Information on all known tumours, age at presentation and diagnosis, and many different symptoms are included. We have analysed details of patients who have been detected as having VS on a screening MRI scan without any known central nervous system pathology, signs, or symptoms. It has been our practice to carry out a baseline MRI …