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Symmetrical predominantly proximal weakness in the legs
Last reviewed: 04.07.2025
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[ Causes of symmetrical predominantly proximal weakness in the legs:
- Motor neuron diseases.
- Myopathies.
- Polyneuropathies.
Motor neuron diseases, such as juvenile spinal muscular atrophies, especially the proximal forms, and less commonly the initially symmetrical form of amyotrophic lateral sclerosis, may lead, depending on the stage of the process, to general weakness or more isolated paralysis in the proximal parts of the legs with fasciculations and marked increase in reflexes or pyramidal signs. But these diseases most often affect the upper limbs; involvement of the lower limbs is usually observed against the background of more generalized motor neuron and muscle disease.
Myopathies in which only or mainly the pelvic girdle and upper thighs are initially affected. These are progressive muscular dystrophy (type II) with pelvic girdle involvement, Duchenne dystrophy (type III), dermatomyositis, etc. Such localization of muscle weakness is rarely observed in myasthenia. Muscle involvement in other diseases accompanied by myopathy is most often noted in the pelvic girdle (as in hyperthyroidism, Cushing's disease, hyperparathyroidism, as well as in the picture of uremia).
Polyneuropathies sometimes occur with proximal accentuation of flaccid paralysis. Such a picture is described in Guillain-Barré syndrome, toxic polyneuropathy in gold and vincristine intoxication, as well as in polyneuropathies against the background of hyperthyroidism, giant cell arteritis, porphyria.