Botulinum toxin in hemifacial spasm: the challenge to assess the effect of treatment

Abstract

Hemifacial spasm is characterized by intermittent tonic or clonic contractions of the muscles supplied by the facial nerve. Although vision is less impaired than in patients with blepharospasm, the disease can impose significant psychosocial burden on patient's life. Botulinum toxin (BoNT) is the well-established pharmacotherapy of choice, but evidence from controlled clinical trials is sparse. There is a broad variety of rating scales used in clinical studies with BoNT and obviously no consensus has been reached how to assess treatment outcome in hemifacial spasm. Clinical rating scales focusing on objective function were used in a couple of controlled studies with BoNT and were appropriate to discriminate between BoNTA and placebo. But it has not been shown that they would be sensitive enough to detect minor differences between several BoNT formulations. Although most of the clinical scales consist of a five-point rating, the descriptors for the ordinal numbers are not necessarily the same so that the results of different clinical studies are not comparable to each other. The main disadvantage of clinical scales is that they do not take into account patient's perspective of disability and impact on daily life. For this reason some clinical studies applied health-related quality of life (HRQoL) questionnaires to assess efficacy, and one research group worked on the development of disease-specific tools. Although these HRQoL questionnaires have been validated and a good correlation to disease severity could be demonstrated, they are far from having become an established variable for efficacy assessment in hemifacial spasm trials. The challenge remains to establish tools which are appropriate to rate BoNT treatment effects in hemifacial spasm. Currently, it is virtually impossible to identify one rating scale which can cover all relevant aspects of the disorder. In consequence we recommend the implementation of a combination of different rating scales which address functional impairment as well as those issues which are most important to patients. Further research is needed to standardize and validate rating scales for hemifacial spasm in clinical studies.

Correlation of Botulinum Toxin Dose with Neurophysiological Parameters of Efficacy and Safety in the Glabellar Muscles: A Double-blind, Placebo-controlled, Randomized Study

“…Nevertheless, these scales are not sensitive enough to detect subtle difference in effect between various BoNT-A formulations or doses (8)(9)(10) or even simple parameters, such as details of the exact onset of action. Neurophysiological studies comparing different BoNT products have mainly analysed the compound motor action potential (CMAP), i.e.…”

The Illness and Treatment Beliefs of Adults with Blepharospasm and Hemifacial Spasm Receiving Botulinum Toxin Injections: A Cross-Sectional Study

“…This study demonstrates patients with movement disorders affecting the face and/or eyes also understand their condition is serious and long-term. Beliefs about more symptoms associated with BEB, and more negative consequences of BEB, than HFS, may be due to the greater likelihood for visual impairment when spasms affect both eyes (BEB) compared to one eye (HFS), a suggestion supported by previous research [20].…”

“…For patients with HFS an additional rating scale measuring the severity and frequency of cheek involvement developed previously for HFS research [20] was used. Higher scores indicate severe and more frequent spasms, with a maximum total score of 8 for each rating scale…”

“…Responses ranged from "no impairment" to "no longer possible due to illness", with a "not applicable" option available for each item and higher scores indicating greater disability. This valid and reliable measure [19] is also recommended for use with patients with HFS [20].…”

Esthetics and dermatologic pharmaceuticals

“…[8][9][10] Throughout the 1980s it was used extensively to treat blepharospasm, 11,12 hemifacial spasm, 13,14 and cervical dystonia. [8][9][10] Throughout the 1980s it was used extensively to treat blepharospasm, 11,12 hemifacial spasm, 13,14 and cervical dystonia.…”