Abstract
Botulinum toxin type A (BTXA) is widely used in neurological therapeutics for a variety of indications such as dystonia, spasticity, hyperhidrosis, and hypersalivation. It is relatively contraindicated in disorders of neuromuscular transmission, in individuals with known hypersensitivity or bleeding disorders, and during pregnancy. Two patients are presented with initially undetermined multisystem neurological disorders and excessive sialorrhoea, later diagnosed as mitochondrial cytopathy, who had side effects after treatment with ultrasound guided BTXA injections. Published reports on the use of BTXA injections in hypersalivation of various causes are reviewed, along with the proposed mechanisms of hypersensitivity to BTXA in patients with mitochondrial cytopathies. Clinicians should be cautious when using BTXA injections in such patients because of the significant risk of side effects.