There are nine different categories used for diagnosis (Table 1.3.2)
The clinical manifestations are determined by the type of muscular dystrophyTable 1.3.1 Considerations for dental management.Risk assessmentProgressive deterioration/poor prognosis (depending on the subtype)Comorbidities may be present (e.g. cardiomyopathy, arrhythmia, hypoventilation and neuropsychiatric disorders)Aspiration risk due to the loss of protective reflexesPressure ulcers (decubitus) may be presentLong‐term use of corticosteroids can result in adrenocortical suppressionRisk of rhabdomyolysis associated with general anaesthesiaCriteria for referralPatients can often be treated in a conventional dental clinic, especially during the initial stages of the diseaseReferral to a specialised clinic or hospital centre is determined by the patient's general condition (e.g. respiratory distress, severe heart disease and highly advanced stages of the disease)Patients with severe muscle contractures and/or medical complications should typically be treated in a hospital settingAccess/positionPhysical assistance for the transferOrthopaedic devices may be wornWheelchair use is commonShort sessions (frequent changes in position)Dental chair positioned at 45°In advanced phases of the disease, emergency dental care may be provided in a home (domiciliary) or hospital settingCommunicationA consultation with the patient's doctor is advisable to determine the degree of disease control and the presence of complicationsOccasionally, the disease is accompanied by intellectual disabilityVerbal communication may be impeded due to dysarthria among their manifestations (e.g. oculopharyngeal muscular dystrophy)Consent/capacityIn most cases, capacity is not impairedInform the patient that the dental treatment plan will need to consider the expected progression and life expectancy in relation to the muscular dystrophyAnaesthesia/sedationLocal anaesthesiaCaution is advised when using local anaesthesia with vasoconstrictors in patients with cardiomyopathy and arrhythmiasSedationAvoid opioids and benzodiazepines for conscious sedation (respiratory depression)General anaesthesiaMay be contraindicated in cases of cardiomyopathy or severe respiratory diseaseEndotracheal intubation can be challenging (due to kyphoscoliosis or neck flexion)Neuromuscular blockers and some inhaled anaesthetics produce respiratory depressionSuccinylcholine administration in patients with Duchenne and Becker muscular dystrophies is associated with life‐threatening rhabdomyolysis and hyperkalaemiaRisk of regurgitation, prolonged hypoventilation and aspiration pneumonia post intubationDental treatmentBeforeAssess the requirement for corticosteroid supplementationAssess the need for mouth propsOrthodontic therapy to improve the chewing function and the airway may be consideredRehabilitation with tooth‐supported and implant‐supported prostheses may be considered (isolated cases have been published)DuringIf mouth opening is impaired, consider careful use of mouth props (exercise increased caution as protective reflexes may be lost)Use rubber dam (decreased protective reflexes)Use a high‐volume suction to prevent aspirationAfterEnsure that the oral cavity is clear of all debrisDrug prescriptionConsider drug interactions with medications used to treat comorbidities (e.g. selective serotonin reuptake inhibitors inhibit several families of hepatic enzymes, which may delay the biotransformation of codeine to its active metabolite)Education/preventionDifficulties maintaining good mechanical oral hygieneDietary counsellingConsider the use of topical fluoride and fluoride varnishFissure sealants may be consideredEstablish regular check‐up visits to control plaque/tartar – increase frequency as muscular control deteriorates
Duchenne muscular dystrophy is the most common amongst children and is characterised by:Inheritance (linked to the X chromosome)Onset in the first years of childhoodInvolvement of all muscles (generalised muscle weakness)Muscle pseudohypertrophy (enlargement)Pelvic girdle muscle impairmentDifficulty standing up (Gowers sign)Severe lumbar lordosis and peculiar gait (‘duck‐like’)Confined to wheelchair before pubertyCardiomyopathyRespiratory impairmentIn some cases, intellectual impairment may be presentDeath in the first years of the adult stage
Diagnosis
The initial diagnosis is based on clinical findings (e.g. generalised muscle weakness)Table 1.3.2 Classification and characteristics of muscular dystrophy.TypeSex Age at onsetMuscles involvedAssociated complicationsLife expectancyDuchenne muscular dystrophyMales3–5 yearsAllCardiomyopathy Intellectual disabilityDie at the end of adolescenceBecker muscular dystrophyMales10–20 yearsAllCardiomyopathy (uncommon)NormalEmery–Dreifuss muscular dystrophyMales<10 yearsAllCardiomyopathy (severe)Die at 30–50 yearsLimb‐girdle muscular dystrophyBoth sexes15–20 yearsPelvic girdle and shouldersCardiomyopathyVariableFacioscapulohumeral muscular dystrophyBoth sexes15–20 yearsFace and shouldersCardiomyopathy (uncommon)NormalMyotonic muscular dystrophy – types 1 and 2Both sexes20–30 yearsAllCardiomyopathy Cutaneous dystrophy Ocular disorders Intellectual disabilityDie at 30–50 years (earlier for type 1)Congenital muscular dystrophyBoth sexesBirthAllRespiratory distress Intellectual disabilityVariableOculopharyngeal muscular dystrophyBoth sexes40–50 yearsUpper eyelids, pharynx, tongueVision problems Dysphagia CardiomyopathyNormalDistal muscular dystrophyBoth sexes40–60 yearsDistalRespiratory distress (in advanced phases)Normal
Blood tests: serum levels of creatine phosphokinase (CPK), aspartate transaminase (AST) and lactate dehydrogenase (LDH)
Electromyography
Muscle biopsy (histopathological and immunological analysis of the muscle) (Figure 1.3.5)
In some types of muscular dystrophy, genetic analysis may be of valueFigure 1.3.5 Diagnostic muscle biopsy showing random variation in fibre size, increase in fibrosis and degeneration of muscle fibres (Masson trichrome staining, ×20).
Management
Physical therapy
Occasionally orthopaedic surgery to help correct the shortening of muscles or to improve scoliosis (Figure 1.3.6)Figure 1.3.6 Orthopaedic surgery to improve scoliosis.
Additionally, cardiac surgery and/or surgery to repair cataracts may be required
Corticosteroids, cardioprotective agents, antidepressants, ventilation with positive non‐invasive pressure
Although there is no known cure, there has been notable progress in correcting the underlying genetic mutations
Prognosis
The prognosis for muscular dystrophy depends on the type and severity of symptoms
However, most individuals do lose the ability to walk and eventually require a wheelchair
Life expectancy is reduced if there is pulmonary dysfunction and/or cardiac involvement
In most cases, the patients die at the end of adolescence or at the start of adulthood, as the consequence of pneumonia or cardiopulmonary failure
A World/Transcultural View
There are major differences between countries in terms of the prevalence of muscular dystrophy. For example, the rate of Duchenne muscular dystrophy in South Africa is estimated at 1 case/100 000 males compared with approximately 17 cases/100 000 males in Sweden
The survival of individuals with some varieties of muscular dystrophy has increased significantly in countries with access to corticotherapy, cardiac medical treatment and mechanical ventilation
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