Botulinum-A toxin in the treatment of craniocervical muscle spasms: short- and long-term, local and systemic effects.

Botulinum toxin has become the initial treatment of choice for the management of essential blepharospasm, hemifacial spasm and other craniocervical dystonias. Numerous studies have confirmed a 90% to 95% response rate. Although a number of common side effects have been reported, the occurrence and incidence of rare local complications remains poorly understood. More importantly, the acute and chronic distant effects of botulinum toxin have not been clearly elucidated. A better understanding of such effects is essential if clinicians are to appropriately advise patients on the use of this therapeutic modality. This article is based on the Duke University experience in the management of over 500 patients with craniocervical spasm disorders, combined with a review of the published literature. These disorders include essential blepharospasm, oromandibular dystonia, hemifacial spasm, and torticollis. The incidence of side effects following more than 6000 treatments with botulinum toxin is presented. Pertinent research relating to the causes of these complications is also reviewed. The most common complications of treatment with botulinum toxin are related to acute local effects resulting from chemodenervation. The most important clinical effect in this group is weakening of the levator muscle resulting in ptosis, and the corneal consequences of lagophthalmos. The latter includes exposure keratitis, dry eyes, blurred vision, and hypersecretion epiphora. Less common local effects include facial numbness, diplopia, and ectropion. Some distant effects are being observed with increasing frequency. These include pruritus, dysphagia, nausea, and a flu-like syndrome. Most significant, however, are the rare reports of generalized weakness and the documentation of EMG abnormalities distant to the site of toxin injection. This has been seen with injections for both blepharospasm and torticollis. Until further studies on the long-term distant complications of botulinum toxin are available, it is recommended that patients receive as few life-time doses of toxin as possible, consistent with adequate management of their spasms. The practice of reinjecting patients routinely every three months, or at the first return of mild spasms should be discouraged.