Muscle Weakness
CASE
A 43-year-old man has a 6-week history of difficulty getting out of bed, arising from a chair, combing his hair, and going up stairs. He has noticed an unusual rash on his knuckles and around his eyelids. He has lost some weight and feels generally fatigued. His examination shows proximal muscle weakness and a rash on his hands and face. His creatine kinase is four times the upper limit of normal.
Diagnosis
Dermatomyositis.
When confronted with a patient who has muscle weakness (Table 11.1), the physician must establish if the weakness is:
Myopathic.
Due to a neuromuscular junction disorder.
Patients with myopathy tend to have stable weakness. It tends to be proximal, affecting hip and shoulder girdle muscles; except in certain dystrophies, which affect more distal muscles. Patients with neuromuscular junction disorders have proximal muscle weakness that is fatigable, as well as ocular, facial, respiratory, and gustatory muscle weakness. Patients with more proximal problems have the associated features of that neurologic structure (see Chapter 1).
HISTORY
In patients with muscle weakness caused by a myopathy, the following occurs:
Weakness is usually symmetric and proximal, with the shoulder and pelvic girdle muscles most severely affected. Climbing stairs, squatting, arising from a chair, and combing the hair are particularly difficult for the myopathic patient.
There are no sensory symptoms (i.e., no “pins-and-needles” sensations or loss of sensation), which are common in neuropathies.
Bowel and bladder function are spared.
Weakness is usually painless.
Cramps may be present, but spasticity is not a feature of the weakness. (Spasticity suggests an upper motor neuron problem.)
TABLE 11.1. Myopathies and Related Disorders | ||||||||||||||||||||||||||||||||||
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In patients with neuromuscular junction disorders, the following occurs:
Weakness tends to be fluctuating, and worse after exercise or later in the day.
Weakness is symmetric and proximal.Related posts:
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