PP> Hemifacial spasm (HFS) consists of involuntary irregular clonic or tonic twitch-like movements of the facial muscles innervated by cranial nerve VII on one side of the face, and is most often a result of vascular compression of the facial nerve at the root exit/entry zone. Non-vascular causes of HFS are less common, and include facial nerve injury, Bell’s palsy, demyelination presumed to involve the facial nucleus and various tumors and space-occupying lesions in the cerebellopontine angle. PP> Twitches usually begin in the periocular region and can progress to the cheek, perioral and platysma muscles. Hemifacial spasm is almost always unilateral. Muscles involved in HFS include the orbicularis oculi, orbicularis oris and zygomaticus predominantly with frontalis, corrugator, nasalis, buccinators, risorius, depressor angularis oris, mentalis and platysma. PP> Injections of botulinum neurotoxin (BoNT) are the preferred treatment of HFS. They are successful in over 90% of patients, with relief lasting approximately 12 weeks, and repeat treatments remaining effective for many years. This chapter lists the pertinent facial muscles along with their principal mechanical actions; illustrates their anatomy under the skin, showing the recommended injection sites; and tabulates the dose ranges of the various toxins in each of the muscles. <COMP: I can’t get rid of the PP coding here without seeming to lose text>

The gingival smile or gummy smile (GS) occurs when more than 2 to 3 mm of gum is exposed. It may be related not only to the excessive elevation of the upper lip by the involved muscles, but also to alterations in anatomical features like lip length, bone and periodontal and dental structures. The amount of exposed gum can largely differ from patient to patient, with some individuals presenting gum exposure of up to 10 mm. This chapter discusses the different subtypes of gummy smile – anterior, posterior, mixed – using detailed anatomical illustrations of each, including the pertinent musculature. A table lists the specific muscles to target for injection in each subtype.

Hyperhidrosis is excessive sweating, beyond physiological needs. It may be divided into generalized and localized/focal types, and into primary/idiopathic and secondary forms. Primary axillary hyperhidrosis appears to be the most frequent type, followed by palmar hyperhidrosis and other patterns. Hyperhidrosis may negatively affect many fields of daily life to a significant extent, including emotional status, personal hygiene, work and productivity, leisure activities and self-esteem.

When injected intra- or subdermally, botulinum neurotoxin (BoNT) blocks the release of acetylcholine from the sympathetic nerve fibers that stimulate the eccrine sweat glands and causes a localized, long-lasting but reversible abolishment of sweating. This chapter describes in detail the techniques for BoNT injection to treat primary axillary and palmar hyperhidrosis, as well as showing treatment of scalp and segmental hyperhidrosis. Techniques for assessing the degree and distribution of hyperhidrosis, the area to be treated and the degree of benefit are described.

Focal hand dystonia (FHD) is characterized by dystonic hand contractions that are often aggravated by purposeful actions and may be specific to a particular task. The term “occupational dystonia” is used when dystonia affecting performance of the job arises in individuals with a particular occupation, usually an occupation requiring repetitive and excessive fine motor activity.

One task-specific FHD, writer’s cramp, causes disabling spasms of the hands when attempting to write, and is particularly likely in people whose profession involves excessive writing. Musician’s dystonia (cramp) is applied to a focal dystonia localized to hand muscles controlling fine movements of the digits or the embouchure muscles involved in playing instruments.

Injection of botulinum neurotoxin (BoNT) is effective in writer’s cramp and other occupational dystonias. This chapter discusses the different common patterns of dystonic movement of the hand and arm, identifies the particular muscles active in each dystonia pattern to aid in target selectio, and illustrates the muscular anatomy and injection approach using anatomical diagrams. Guidance of injections with EMG is discussed. Dosing recommendations for three different BoNT formulations are tabulated.