A clinical, genetic and audiological study of patients and families with bilateral acoustic neurofibromatosis.

The neurofibromatoses consist of at least two distinct autosomal dominant hereditary disorders. Neurofibromatosis type 1 (NF1) is due to a lesion on chromosome 17q. Neurofibromatosis type 2 (NF2) is caused by a defect on chromosome 22q. The hallmark of NF2 is the development, in the second and third decades, of bilateral acoustic neuromas. NF1 is characterized by the appearance of café-au-lait spots and neurofibromas in addition to iris hamartomas, or Lisch nodules, of the eye, during the first and second decades. Ten families were personally studied. A total of 16 members were found to be affected with NF2. A protocol for evaluation and review of subjects and relatives of NF2 families is proposed. A team approach, coordinating the expertise of multiple specialties is recommended.

Criteria for hearing preservation in acoustic schwannoma surgery: the concept of useful hearing.

In the quest for hearing preservation in patients with acoustic schwannomas it is essential that surgeons do not lose sight of the concept of 'useful' hearing. There is an important difference between hearing preservation which pleases the surgeon and that which will be appreciated by the patient. Tumour size, pure tone audiogram average differences between ears and speech discrimination scores have been recorded in a series of 114 patients with unilateral acoustic schwannomas. Criteria for useful hearing are presented in terms of pure tone audiogram average difference and speech discrimination scores. There were 11 patients (10 per cent) with a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 30 dB or better and a tumour size of no more than 2 cm. Only one patient (0.9 per cent) had a speech discrimination score of 50 per cent or more, a pure tone audiogram average difference of 20 dB or better and a tumour size of no more than 1 cm. It is concluded that hearing preservation techniques may be applicable to between 1 and 10 per cent of patients with unilateral acoustic schwannomas.

Acoustic neuroma (schwannoma) surgery 1978-1990.

A series of 151 patients with 154 acoustic schwannomas have been operated upon in Manchester Royal Infirmary by a joint Otological and Neurosurgical team, employing either the translabyrinthine or the suboccipital approach. The perioperative mortality rate was 3 per cent. Anatomical preservation of the facial nerve was achieved in 89 per cent of tumour removals and a good to normal functional result in 79 per cent of cases. Attempts at hearing preservation have been unsuccessful, largely because of the small number of patients in the series in whom useful hearing was present preoperatively. Complications included major brain stem ischaemia (1.2 per cent), CSF fistula (5 per cent) and facial dysaesthesia (7 per cent). The incidence of mortality and morbidity is directly related to tumour size and to the experience of the surgeons. A number of patients experienced an unusual type of post-operative dreamlike state which appeared to be a form of hypnagogic hallucination, and the possible neurophysiological mechanism responsible for this phenomenon is discussed. The continuing failure to attain the ideal of early diagnosis is lamented, and the importance of a flexible bidisciplinary surgical approach emphasized.

Isoelectric focusing of ferredoxins, flavordoxins and a rubredoxin.

Isoelectric points of ferredoxins, flavodoxins and a rubredoxin from a range of sources were measured by electrofocusing over the pH range between 2.5 and 5.0 on thin layers of polyacrylamide gel. The pH gradient along the gel was measured directly by a surface electrode. The isoelectric points of the plant-type ferredoxins were between approx. 3.15 and 3.35, and those of the flavodoxins close to 3.5. Ferredoxin, rubredoxin and flavodoxin from Clostridium pasteurianum had isolectric points of the of 2.75, 2.9, and 3.1, respectively. The values for the isoelectric points ferredoxins are significantly lower than previous results in the literature suggest.