A 22-year-old man with a strong family history of muscular dystrophy (his father and one brother) complained of difficulty raising his arms. He denied weakness in the legs.
On examination, there was a mildly asymmetric smile and weak orbicularis oculi and oris muscles. Cranial nerves were otherwise normal. There was bilateral atrophy and weakness of the spinati, pectoralis, biceps, and trapezius muscles ( Fig. 85-1 ). The deltoids were not atrophic and were strong when the shoulder was fixed by the examiners; there was prominent winging of the scapulae, as well as weakness of the biceps and triceps muscles. Distal upper extremity and lower extremity strength were normal. Reflexes were normal and symmetrical; coordination was intact; sensation was also normal to all modalities. No fasciculations were seen. There were no Babinski signs, and the rest of the neurologic examination was unremarkable.
Fig. 85-1
Patient showing a mildly asymmetric smile and a trapezius “hump,” as this muscle is atrophic and its apparent prominence is the elevated scapulae.
What is the Differential Diagnosis?
Spinal muscular atrophy is a consideration, but in these patients there is limb weakness and areflexia, and facial weakness is seen only rarely. Myasthenia gravis and myasthenic syndromes can affect facial muscles, but these are fluctuating rather than progressive, and patients usually do not have muscle atrophy. Polymyositis is another consideration, but this disease is not hereditary and only rarely affects the facial muscles. Mitochondrial myopathies can have limb and facial muscle weakness but also ophthalmoplegia, and the inheritance is not autosomal-dominant. Scapuloperoneal syndromes affect the scapulae and distal leg muscles, sparing the face.
The most likely diagnosis is facioscapulohumeral muscular dystrophy (FSHD), based on the positive family history of apparent autosomal-dominant inheritance, with facial as well as scapular and arm weakness and prominent winging of the scapulae.
An EMG Test was Performed
Motor Nerve Studies
Nerve and Site
Latency (ms)
Amplitude (mV)
Conduction Velocity (m/s)
Median Nerve R.
Normal ≤ 4.2
Normal ≥ 6
Normal ≥ 50
Wrist
3.5
16
–
Elbow
7.3
16
57
Ulnar Nerve R.
Normal ≤ 3.6
Normal ≥ 8
Normal ≥ 50
Wrist
3.0
10
–
Below elbow
7.4
10
54
Above elbow
9.4
10
60
Nerve and Site
Latency (ms)
Amplitude (mV)
Conduction Velocity (m/s)
Peroneal Nerve R.
Normal ≤ 5.7
Normal ≥ 3
Normal ≥ 40
Ankle
3.9
8
–
Fibular head
10.6
8
44
Knee
12.8
8
45
F-Wave Studies
Nerve
Latency (ms)
Normal Latency ≤ (ms)
Median nerve R.
26.4
30
Ulnar nerve R.
26.7
30
Peroneal nerve R.
48.9
54
Sensory Nerve Studies
Nerve
Onset Latency (ms)
Normal Onset Latency ≤ (ms)
Peak Latency (ms)
Normal Peak Latency ≤ (ms)
Amp (μV)
Normal Amp ≥ (μV)
Conduction Velocity (m/s)
Normal Conduction Velocity ≥ (m/s)
Median nerve R.
2.4
2.6
2.9
3.1
35
20
54
50
Ulnar nerve R.
2.2
2.6
2.7
3.1
18
13
55
50
Superficial peroneal nerve R.
3.1
3.5
3.6
4.0
16
8–10
45
40
EMG Data
Muscle
Insrt Activity
Fibs
Pos Waves
Fasc
Amp
Dur
Poly
Pattern
Trapezius R.
Norm
None
None
None
Dec
Brief
Many
Full
Infraspinatus R.
Norm
None
None
None
Norm
Norm
None
Full
Deltoid R.
Norm
None
None
None
Norm
Norm
None
Full
Biceps brachii R.
Norm
None
None
None
Dec
Brief
Many
Full
Triceps R.
Norm
None
None
None
Norm
Norm
None
Full
First dorsal interosseous R.
Norm
None
None
None
Norm
Norm
None
Full
Trapezius L.
Norm
None
None
None
Dec
Brief
Many
Full
Biceps brachii L.
Norm
None
None
None
Dec
Brief
Many
Full
Vastus lateralis R.
Norm
None
None
None
Norm
Norm
None
Full
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