Q 4 WRITE A NOTE ON PATTERN RECOGNITIONS AND SIGNS IN CLINICAL EVALUATION OF A MYOPATHY ?
A 4 INTRODUCTION
1 Myopathies are disorders affecting either the channel, structure or metabolism of skeletal muscle.
2 Myopathies can be distinguished from other disorders of the motor unit, including the neuromuscular junction, peripheral nerve, or motor neuron, by characteristic clinical and laboratory features.
3 Therefore, the first goal in approaching a patient with a suspected muscle disease is to determine the correct site of the lesion.
4 Once the lesion is localized to the muscle, the next step is to identify whether the myopathy is due to a defect in the muscle channel, muscle structure, or a dysfunction in muscle metabolism.
5 The second goal is to determine the cause of the myopathy.
6 In general, myopathies can be classified into acquired or hereditary disorders
7 Finally, the third goal in the approach is to determine if there is a specific treatment, and if not, to optimally manage the patient’s symptoms in order to maximize their functional abilities and enhance their quality of life.
COMPONENTS
A ) The most important component of evaluating a patient with a suspected myopathy is obtaining a comprehensive medical history.
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B ) Which “negative” and/or “positive” symptoms does the patient demonstrate?
1 Symptoms of muscle disease can be divided into 2 -
A ) “negative” complaints such as exercise intolerance, fatigue, muscle atrophy and weakness
B ) “positive” complaints such as contractures, cramps, myalgias, muscle stiffness and myoglobinuria.
C ) Weakness is by far the most common “negative” symptom reported by a patient with muscle disease When the upper extremities are involved, patients notice trouble brushing their teeth, combing their hair or lifting objects overhead.
D ) If the weakness involves the lower extremities, patients will complain of difficulty arising from a low chair or toilet, getting up from a squatted position, or climbing stairs.
1 These symptoms in the arms and legs indicate proximal muscle weakness, which is probably the most common distribution of weakness in a myopathic disorder
E ) Many patients who complain of generalized weakness or fatigue do not have a myopathy, particularly if the neurologic examination is normal. On the other hand, it is important to define the intensity and duration of exercise that provokes the fatigue since metabolic and mitochondrial myopathies can cause abnormal fatigability after exercise
F ) Muscle cramps are a specific type of muscle pain.
1 They are typically benign, occurring frequently in normal individuals, and are seldom a feature of a primary myopathy.
2 Cramps commonly occur due to dehydration, hyponatremia, azotemia, myxedema and disorders of the nerve or motor neuron (especially amyotrophic lateral sclerosis), or most often are benign and not related to an underlying disease process.
3 Cramps may last from seconds to minutes and are usually localized to a particular muscle region, typically the calves.
4 Cramps are characterized by rapidly firing motor unit discharges on needle electromyography.
G ) Muscle contractures are uncommon but can superficially resemble a cramp.
1 They are typically provoked by exercise in patients with glycolytic enzyme defects.
2 Contractures differ from cramps in that they usually last longer and are electrically silent with needle electromyography.
3 Muscle contractures should not be confused with fixed tendon contractures