Bunny lines are defined as wrinkles on the lateral and/or dorsal aspect of the nose. They may be naturally present in some clients when they smile, laugh, frown or speak. However, they may appear or even become worse after treatment with botulinum toxin, especially in the crow’s feet and glabella area.
Clients usually blame the aesthetician if those lines result from the injection of botulinum toxin for any cosmetic treatment. When blocking a specific muscle, it is more likely that its synergistic muscle may contract as well and sometimes may even react with over contraction. When the eye and nose complex is under animation, there is parallel contraction of the corrugators, procerus, nasalis and orbicularis oculi and, depending on the client, the upper lip elevators as well.
The most common treatment with botulinum toxin in the upper third includes the blocking of the frontalis, corrugators, procerus and orbicularis oculi. If the nasalis is not treated, undesired bunny lines can appear. Depending on the skincomplexion, there will be more or less wrinkle formation. For example, clients with thin skin and a fair complexion are more prone to develop wrinkling on the nasal dorsum and lateral walls. Sometimes, these extend to the lower eyelid. Darker complexion and oily skin produce thick wrinkling and are usually limited to the nasal dorsum. The choice of treating the bunny lines concomitant with crow’s feet or glabella area all depends on the client. If they are not treated during the same session, and become too evident after the treatment, they may be treated afterwards.
The skin is thinner and more mobile in the upper two thirds of the nose, and it is thicker and more adherent in the lower third portion of the face. The thinner and older the skin is, the more wrinkling is to be formed on the nasal dorsum. The nose contains three main muscles: the procerus, the nasalis and the depressor septi nasi. The procerus draws the medial part of the eyebrow down. It originates at the nasal root and blends with the frontalis fibres. The depressor septi nasi drops the tip of the nose when contracted. Finally, the m. nasalis is the most important one for causing the bunny lines and will be the main focus of treatment. Although the m. levator labii superioris alaeque nasi is not an intrinsic nasal muscle, it can contribute to the bunny lines due to its medial fibres. The nasalis originates in the transition from the nasal bone with the maxilla and inserts into the aponeurosis of the nasal dorsum. It looks like an upside-down horseshoe, with the upper or curved part formed by transverse fibres on the nasal dorsum. Its action is to narrow the nostrils (also denominated as compressor naris). The transverse fibres of the nasalis lead, when contracted, to the lateral nasal lines and to additional lines in the internal infra-ocular region. The two lower parts of the nasalis run vertically down the sides of the nose (also known as the dilator nasi) and their action is to open the nostrils.
Aim of the Treatment
The aim of the treatment is to reduce bunny lines; either those naturally present or those appearing after treatment of the glabella and crow’s feet area with botulinum toxin. Bunny lines may be treated alone or in conjunction with the treatment of the crow’s feet and glabellar lines. Kinetic patients usually do not present lines on the nasal dorsum when smiling and concurrent treatment with crow’s feet may not be required. In static analysis, hyperkinetic and hypertonic clients may present with wrinkles on the nasal dorsum.
The presence of those lines at rest indicates the need for bunny line treatment at the same time as with crow’s feet and glabellar lines. During animation, clients should be asked to laugh, to sniff and to squint intensely as if a very bright light is in front of their eyes. Usually, bunny lines are not present in kinetic clients with a mild smile. They only become evident when smiling at maximum contraction. In hyperkinetic patients, bunny lines are found with a mild smile and become worse at maximum contraction. Due to constant squinting, the m. nasalis may become hypertrophic and may reduce the duration of effect of botulinum toxin at the nasal level. Bunny lines may be limited to the nose, with an extension to the lower eyelid and reach the nasal flare. Depending on the client, they may be present only at the lateral aspect of the nasal dorsum or at the upper aspect of the nasal bone.
After static and dynamic evaluation, the injection points should be marked on the lateral and upper aspect of the nasal bone if needed. The injection should be very superficial because the skin at this level is very thin and contact with the periosteum can be painful. The needle should be at an angle of 30 degrees, because it is easier to avoid touching the periosteum. There is an evident papule or wheal formation after the injection.
Care should be taken with blood vessels at this level, otherwise bruising may result. A total dose of 2–5 units of botulinum toxin should be distributed on both lateral sides. In selected clients an extra dose from 1 to 2 units of botulinum toxin may be injected in the midline. It is important not to inject too laterally down the nasal sidewalls; otherwise, the levator labii superioris alaeque nasi may be blocked and upper lip ptosis and asymmetry may result. Care should be taken to avoid injection into the angular vessels which would produce bruising and ecchymosis. Partial or no effect often results from inadvertent injection into the blood vessels.
Treatment of bunny lines
• Two injection points, one for each side of the nose. In certain cases, an additional medial point may be added
• Botulinum toxin dose: 2–5 units total dose for the two points, 1–2 units for the extra point
The most common complication with the treatment of bunny lines is the presence of ecchymosis or hematoma. An unsatisfactory result may be due to inadvertent injection into the blood vessels. Major problems such as diplopia and upper lip ptosis may result from inadvertently blocking the rectus inferioris or medialis and the levator labii superioris alaeque nasi, respectively. More serious complications can include speaking and chewing difficulty.