title: Unilateral masseter muscle hypertrophy: morphofunctional analysis of the relapse after treatment with botulinum toxin.
abstract: This is a case of unilateral masseter muscle hypertrophy (MMH) treated with botulinum toxin (NHAI-normalised hemi-facial asymmetry index improvement from 5.48 to 3.04). After 19 months the treatment was repeated because of hypertrophy relapse (NHAI increase up to 6.82). The volume variations in the masseter area were monitored during 25 months using a laser scanner to compute facial volume. In order to relate the cause of hypertrophy and relapse to the presence of parafunctional activities, a nocturnal electromyography (EMG) study was conducted with positive results (nocturnal parafunctions of patients 4074.99 microV to be compared with a control group value of 1644.63 microV). The lack of the left inferior molars and the consequent right occlusal support seemed to justify the hypertrophy of right masseter (MMRight-POC [percent overlapping coefficient] 91.9%). However, the prosthetic rehabilitation did not prevent relapse in the same muscle. The EMG analysis of both the muscular activation (MMRight-POC 66.0% after relapse) and inhibition activity in Maximum Voluntary Clench (MVC) resulted in contradictory conclusions. At present, the available knowledge regarding MMH physiopathology is very limited and does not support a therapeutic rationale for relapse prevention.
authors.affiliation: Maxillofacial Surgery School, University of Padova, Italy. redentop@tin.it
authors.forename: Redento
authors.initials: R
authors.lastname: Peretta
authors.forename: Marco
authors.initials: M
authors.lastname: Melison
authors.forename: Roberto
authors.initials: R
authors.lastname: Meneghello
authors.forename: Daniele
authors.initials: D
authors.lastname: Comelli
authors.forename: Luca
authors.initials: L
authors.lastname: Guarda
authors.forename: Pier Francesco
authors.initials: PF
authors.lastname: Galzignato
authors.forename: Gianmaria
authors.initials: G
authors.lastname: Concheri
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Ferronato
mesh_terms: D000328:Adult; D019274:Botulinum Toxins, Type A / Q000627:therapeutic use*; D002508:Cephalometry; D004576:Electromyography; D007839:Functional Laterality; D006801:Humans; D006984:Hypertrophy / Q000188:drug therapy; D008297:Male; D008406:Masseter Muscle / Q000187:drug effects / Q000473:pathology* / Q000503:physiopathology; D009135:Muscular Diseases / Q000188:drug therapy / Q000473:pathology* / Q000503:physiopathology; D009465:Neuromuscular Agents / Q000627:therapeutic use*; D012008:Recurrence; D017211:Treatment Failure
chemical_list: D009465:Neuromuscular Agents; D019274:Botulinum Toxins, Type A