Proximal Muscular Dystrophy

At a glance

Inherited symmetric proximal muscular weakness, initially of the lower limbs, with slow progression and associated cardiac anomalies.

Synonyms

Limb-Girdle Muscular Dystrophy; Leyden-Möbius Muscular Dystrophy; Pelvifemoral Muscular Dystrophy; Scapulohumeral Muscular Dystrophy.

History

The earliest description of the proximal muscular dystrophy is described to Leyden and Möbius in 1876 and 1879, respectively. They described adult patients with pelvic and femoral distribution of weakness and atrophy with a benign course. At that time, the differentiation between the spinal muscular atrophies and weakness associated with central nervous system (CNS) disorders and primary muscle disease had not been established.

Incidence

Exact figures are not available. There is no racial predilection and it affects either sex equally.

Genetic inheritance

Limb-Girdle Muscular Dystrophy Type 1 is autosomal dominant and Limb-Girdle Muscular Dystrophy Type 2 is autosomal recessive inherited.

Pathophysiology

The pathophysiology of the proximal muscular dystrophies depends on the specific genetic defect of each associated condition and is discussed with each individually in this book.

Diagnosis

Of the various muscular dystrophies, the dystrophinopathies are the most common, accounting for the majority of male disease and 10% of female patients presenting for muscular dystrophy or persistent high serum creatine kinase.

Clinical aspects

Limb-Girdle Muscular Dystrophy Type 1 is characterized by adult onset of proximal muscle weakness, beginning in the hip girdle region and later progressing to the shoulder girdle region. In Limb-Girdle Muscular Dystrophy Type 2 the symmetric muscular weakness starts proximal in the lower extremities usually before the age of 20 years. Distal muscle weakness may occur later. There is a slow progression over the next 10 to 20 years, which also results in weakness of the upper limb. In contrast to ☞Bethlem Myopathy and ☞Emery-Dreifuss Muscular Dystrophy, contractures of the elbows and the Achilles tendon are absent or subtle. Cardiologic abnormalities (atrioventricular conduction defects with arrhythmias and risk of sudden death) occur in almost two-thirds of these patients. Rarely, dilated cardiomyopathy may be present. In general, neuromuscular symptoms precede cardiac abnormalities. Serum creatine phosphokinase levels are usually elevated.

Anesthetic considerations

Cardiac evaluation with ECG and echocardiography is recommended. If the patient already has a pacemaker, ensure proper function. Although congenital myopathies have been associated with malignant hyperthermia, the evidence supporting this causal relationship is poor for Limb-Girdle Muscular Dystrophies. No case reports of malignant hyperthermia reaction in proximal muscular dystrophy have been published.

Pharmacological implications

If nondepolarizing muscle relaxants are to be used, they should be titrated to effect by using a peripheral nerve stimulator. Cis-atracurium can be used ...