Clinical approach to the diagnostic evaluation of hereditary and acquired neuromuscular diseases

Abstract

For diagnostic evaluation of a neuromuscular disease, the clinician must be able to obtain a relevant patient and family history and perform focused general, musculoskeletal, neurologic, and functional physical examinations to direct further diagnostic evaluations. Laboratory studies for hereditary neuromuscular diseases include the relevant molecular genetic studies. The electromyogram and nerve-conduction studies remain an extension of the physical examination, and help to guide further diagnostic studies such as molecular genetics and muscle and nerve biopsies. All diagnostic information needs are to be interpreted within the context of relevant historical information, family history, physical examination, laboratory data, electrophysiology, pathology, and molecular genetics.

Figure 1

Child with Duchenne muscular dystrophy; note the calf hypertrophy, mild equinus posturing at the ankles, shoulder retraction, and mild scapular winging.

Figure 2

Pseudohypertrophy of the posterior deltoid muscle and posterior axillary depression sign in Duchenne muscular dystrophy.

Figure 3

a) adult with characteristic facial characteristics associated with myotonic muscular dystrophy (DM1). Note the long drawn face, temporal wasting, and male pattern baldness. B) Four year old child with congenital myotonic muscular dystrophy (DM1). Note the triangular or “tent-shaped” mouth and slight temporal wasting.

Figure 4

Young adult with Facioscapulohumeral Muscular Dystrophy (FSHD). Note the posterior and lateral scapular winging, the high riding appearance of the scapula, and the asymmetry of winging in the photo on the right.

Figure 5

Hyperkeratosis pilaris (is a fine erythematous popular rash on the back and extensor surface of the upper arm) on the left (A) and distal joint hyperlaxity on the right (B) in a patient with Ullrich congenital muscular dystrophy

Figure 6

Facial weakness of orbicularis oculi in Facioscapulohumeral Muscular Dystrophy (FSHD). Eye closure is weak and weakness of orbicularis oris produces difficulty smiling, puffing out the cheeks, and pursing the lips.

Figure 7

Child with severe SMA II, with hypotonia and chest wall wasting creating a bell-shaped chest.

Figure 8

Examination for neck flexor weakness in Duchenne muscular dystrophy.

Figure 9

Percussion myotonia in myotonic muscular dystrophy (DM1).

Figure 10

Gower’s sign in a seven-year-old boy with Duchenne muscular dystrophy

Figure 11

Myopathic gait pattern in Duchenne muscular dystrophy due to pelvic girdle and knee extension weakness; a) lumbar lordosis to keep center of mass posterior to hip joint; anterior pelvic tilt due to hip extensor weakness; weight line/center of mass maintained anterior to an extended knee; and forefoot ground contact with stance phase plantar flexion (toe walking) to maintain a knee extension moment and knee stability; b) trendelenberg or “gluteus medius gait” with lateral lean over the stance side due to hip abductor weakness; ankle dorsiflexion weakness necessitates swing phase circumduction for clearance.

Figure 12

Four individuals with myotonic muscular dystrophy. The mother on the left (a) has 75 CTG repeats in the DM protein kinase (DMPK) gene loci on chromosome 19q13.3 and her daughter has 2538 CTG repeats. The mother on the right (a) is more symptomatic and has 450 CTG repeats and her daughter has 1650 repeats. This is an example of genetic anticipation with greater severity occurring in successive generations.