²The Eye Unit Pembury Hospital Pembury, Kent, UK

A 48-year-old woman complained of sensation of heaviness of the eyelids and distortion of the upper lids 1 week following botulinum toxin injection to the upper forehead. A total of 15 U of Botox (Allergen) were diffusely injected into the forehead wrinkles. Examination revealed a smooth forehead with absent frontalis action. The eyebrows were in normal position and lid closure was unaffected. However above both skin creases, there were redundant folds of skin overhanging the skin creases (Figure 1). Manual elevation of the eyebrows caused the skin to disappear (Figure 2). Reviewing of the photographs taken before the treatment showed bilateral high eyebrows with apparent frontalis overaction. Paralysis of the frontalis led to unmasking of latent dermatochalasis. The patient was given the choice of upper lid blepharoplasty. However, she decided to wait for the effect of treatment to disappear before deciding on surgery.

Case 2

A 52-year-old woman complained of upper lid heaviness, and noticing excess of skin when applying eye make-up 2 weeks following injection of botulinum toxin to the upper forehead. She underwent the injection in the hope that it may prevent the development of future forehead wrinkles. Examination revealed absent frontalis action with normal eyelid position but with folds of redundant skin overhanging the skin creases (Figure 3). Manually elevating the lids removed this overhang, and a diagnosis of latent dermatochalasis unmasked by botulinum rejuvenation was again made. She also declined upper lid blepharoplasty. When the frontalis action returned 3 months later there was disappearance of the dermatochalasis (Figure 4). The patient did not undergo further botulinum toxin injection.

Discussion

Overactivity of facial muscles in actions such as frowning, squinting, and raising the eyebrows can lead to premature signs of ageing such as forehead frownlines, glabellar creases, and crow's feet. The onset of these facial features of ageing can be slowed by the use of botulinum toxin-induced chemodenervation of the muscles of facial expression.^3,4 Botulinum toxins are toxins produced by Clostridium botulinum. There are seven serotypes (A-G) of botulinum toxins. Of these, A is the most potent and was the first to be made commercially available for therapeutic use. In the UK, botulinum toxin type A (BTX-A) is available in two forms: Botox (produced by US company Allergan Inc.) and Dysport (produced by the UK company Ipsen Ltd). The potency of the two products is not directly comparable unit for unit; as Botox being three to five times more potent than Dyport.⁵ The toxin produces a nondepolarising block at the level of the neuromuscular junction by binding to acetylcholine receptors of the striated muscle leading to a flaccid paralysis. The onset of action begins after about 72 h, while the duration of action ranges between 3 and 8 months with a mean of 4 months. The effect is only temporary because the muscle generates extrajunctional acetylcholine receptors and the nerve, in turn, sprouts and reinnervates the muscle.^6,7 To date, there have been no long-term adverse effects to the use of BTX-A.

In dermatochalasis, there is redundant skin between the skin crease of the upper lid and the eyebrows that can lead to a sense of heaviness in the eyelids, and in severe cases can be cosmetically unsightly and even impair visual function. Upper lid blepharoplasty is a safe and effective procedure of treating the condition.^8,9 In a subsection of patients, there is a latent dermatochalsis because of the elevating action of frontalis. Consequently, loss of frontalis action can make this excess skin become apparent as a manifest dermatochalsis.

To anticipate the possibility of this occurring is an important part of the assessment of the patient prior to the use of botulinum toxin for cosmetic purposes. It is therefore important to assess the effect of frontalis action on the periorbital regions. By relaxing frontalis and then stabilising the muscle manually, it is possible to assess whether there is any significant redundant skin above the lid crease that could lead to a subsequent dermatochalsis following otherwise successful treatment of forehead wrinkles. If there is this risk then the patient can be counselled and treated accordingly either by reducing the dose of the botulinum toxin given or performing upper lid blepharoplasty if the dermatochalasis fails to improve.

The unmasking of latent dermatochalasis is a potential complication of the use of BTX-A in the treatment of forehead wrinkles. Thorough preoperative assessment of these patients can identify those at risk of this problem and thus reduce the risk of the complication.

Proprietary/Financial interest: None.

2 Carruthers A, Carruthers J. Clinical indications and injection technique for the cosmetic use of botulinum-A exotoxin. Dermatol Surg 1998; 24: 1189-1194. PubMed

3 Foster JA, Wulc AE, Barnhorst D, Papay F. The use of botulinum A toxin to ameliorate Facial dynamic lines. Int J Aesthet Reconst Surg 1996; 4: 137-144.

4 Lowe NJ. Botulinum toxin type A for facial rejuvenation: US and UK perspectives. Dermatol Surg 1998; 24: 1216-1218. PubMed

5 Moore P. Handbook of Botulinum Toxin Treatment. 1st edn. Blackwell Science Publication: Oxford, 1999.

6 Horn A, Porter JD, Evinger C. Botulinum toxin paralysis of the orbicularis oculi muscle. Types and time course of alterations in muscle structure, physiology and lid kinematics. Exp Brain Res 1993; 96: 39-53. PubMed

7 Simpson LL. Kinetic studies on the interaction between botulinum toxin type A and the cholinergic neuromuscular junction. J Pharmacol Exp Ther 1980; 212: 16-21. PubMed

8 Putterman AM, Cosmetic Oculoplastic Surgery, Vol II, 3rd edn. WB Saunders. Philadelphia: 1999, pp 77-90.

9 Baylis HI, Golberg RA, Kerivan K, Jacobs J. Analysis and treatment of the ageing face. Dermatol Clin 1997; 15(4): 635-647. PubMed