Visual side effects from botulinum toxin type B injections

Botulinum toxin B (BotB) has been used to treat hyperhidrosis and cervical dystonia. The most common side effects reported by the manufacturer in clinical trials are xerostomia, dysphagia, dyspepsia, and injection site pain. We describe three cases exhibiting visual symptoms after BotB injection. Case 1. A 26 year-old male with a 6 year history of hyperhidrosis was injected with 20,000 units of BotB in both axillae and palms, on two different occasions. He developed blurry near vision in 4-7 days which lasted 2.5-3 months. While symptomatic examination by a neuro-ophthamologist revealed a parasympathetic abnormality of the ciliary muscles and papillary sphincters bilaterally. Case 2. A 20 year-old female with a 7 year history of hyperhidrosis, was injected with 10,000 units of BotB in both axillae. Two weeks later she developed blurry near vision and ptosis of her left eyelid. Her visual changes returned to baseline in 6 weeks. Case 3. A 32 year-old female with 13 year history of torticollis was injected with 30,000 units of BotB into her cervical musculature. She developed blurred vision when attempting to read 10 days post injection, which resolved in 8 weeks. Because of the side effects she was injected in the same site with 20,000 units, and no visual symptoms were noted. All of these patients elected to continue with a dosing regimen that alleviated the symptoms of their disease, despite the visual effects. Injection of BotB may result in prolonged but self-limiting ophthalmologic adverse effects. All of the patients chose to have blurry near vision over the symptoms of their disease. These patients did not report problems with daily living while suffering from visual changes. Whether this visual impairment will threaten the safety or livelihood of other patients is not known.