Safety and efficacy of botulinum toxin type A following long-term use

Botulinum toxin serotype A (BoNT-A) has long heritage of use leading to confidence in its safety and efficacy. The application of BoNT-A does not lead to persistent histological changes in the nerve terminal or the target muscle. Clinical trials defined the safety and tolerability profile of BoNT-A across common therapeutic indications and showed an incidence of adverse events of approximately 25% in the BoNT-A-treated group compared with 15% in the control group. Focal weakness was the only adverse event to occur more often following BoNT-A treatment. Long-term BoNT-A administration has been assessed in various treatment settings, with the level and duration of BoNT-A efficacy response being maintained over repeated rounds of injection with no major safety concerns. The treatment of children with cerebral palsy often require long-term, repeated, multimuscle BoNT-A injections that lead to the administration of comparably higher toxin doses. Despite the high total body doses used, their distribution over multiple muscles and injection sites means that systemic side effects are rare. Recent formulation changes have reduced the incidence of antibody development following treatment with BOTOX^®. These findings show long-term BoNT-A treatment to be both safe and efficacious for a wide variety of indications.     

Malignant peripheral nerve sheath tumour of the cervical vagus nerve in a neurofibromatosis type 1 patient.

One serious complication of neurofibromatosis type 1 (NF1) is the development of malignant peripheral nerve sheath tumours (MPNSTs). These malignancies often develop within pre-existing plexiform neurofibromas and their development is now thought to be associated with both tumour suppressor gene mutations and dysregulated growth factor signalling. Recent work demonstrates that the lifetime risk of malignant transformation is significantly greater than previously thought. Ionising radiation, a long-standing disease, particularly the presence of a large number of plexiform neurofibromas from an early age, are suggested risk factors. We present an NF1 patient who developed an MPNST of the cervical vagus nerve which was successfully treated with surgery. Close monitoring of patients with NF and a high level of suspicion towards rapidly enlarging and painful swellings is merited as these features may signify malignant transformation. Whether a positive history of MPNST in other affected family members predisposes the individual to a higher risk of malignant transformation is unclear.     

Novel explant model to study mechanotransduction and cell-cell communication.

To understand in situ behavior of osteocytes, we characterized a model of osteocytes in their native bone matrix and demonstrated real-time biologic activity of osteocytes while bending the bone matrix. Using 43 male Sprague-Dawley rats, dumbbell-shaped explants were harvested from stainless steel femoral implants after 6-12 weeks and incubated in culture medium or fixed. Sixteen specimens were used to determine bone volume density (BV/TV), volumetric bone mineral density (BMD) and histology for different implantation periods. Osteocyte viability was evaluated by L-lactate dehydrogenase (LDH) activity in 12 cultured explants. Confocal microscopy was used to assess tracer diffusion in three explants and changes in osteocyte pH of a mechanically loaded explant. From 6 to 12 weeks, explant BV/TV and volumetric BMD trended up 92.5% and 101%, respectively. They were significantly and highly correlated. Tissues were uniformly intramembranous and all bone cell types were present. Explants maintained LDH activity through culture day 8. Diffusion at 200 microM was limited to 1,209 Da. Explants appeared capable of reproducing complex bone biology. This model may be useful in understanding osteocyte mechanotransduction in the context of a physiologically relevant bone matrix.