Proximal limb-girdle palsies presenting as inability to raise the arms or to arise from a squatting, kneeling, or sitting position This is the common pattern of a number of myopathies. Polymyositis, IBM, dermatomyositis, and the muscular dystrophies most often manifest themselves in this fashion. The endocrine and the acquired metabolic myopathies (e.g., Cushing disease, hyperthyroidism, and steroid or statin administration) are other typical causes. Proximal limb weakness is a feature of myasthenia but almost always after the development of ocular or pharyngeal involvement. The childhood Duchenne, Becker, and limb-girdle types of dystrophies tend first to affect the muscles of the pelvic girdle, gluteal region, and thighs, resulting in a lumbar lordosis and protuberant abdomen, a waddling gait, and difficulty in arising from the floor and climbing stairs without the assistance of the arms. Climbing up by placing the hands on the thighs (Gower sign) is particularly characteristic of the dystrophies. Facioscapulohumeral dystrophy affects the muscles of the face and shoulder girdles foremost, and it is manifest by incomplete eye closure, inability to whistle and to raise the arms above the head, winging of the scapulae, and thinness of the upper arms with preserved forearm bulk (“Popeye” effect). Certain early or mild forms of dystrophy may selectively involve only the peroneal and scapular muscles. In milder forms of polymyositis, weakness may be limited to the neck muscles or to the shoulder or pelvic girdles.
A number of other diseases of muscle may express themselves by a disproportionate weakness of girdle and proximal limb musculature. An intrinsic metabolic myopathy, such as the adult form of acid maltase deficiency and the familial types of periodic paralysis, may affect only this region. The congenital myopathies (central core, nemaline, myotubular) cause a relatively nonprogressive weakness of girdle muscles more than distal ones. Proximal muscles are occasionally implicated in spinal muscular atrophy or late onset type and in Kennedy bulbospinal atrophy.
Bicrural palsy presenting as lower leg weakness with inability to walk on the heels and toes, or as paralysis of all leg muscles With the exception of certain distinctive distal types of muscular dystrophies, this pattern, usually due to weakness of peroneal, anterior tibial, and thigh muscles, is usually not a result of myopathy. Symmetrical weakness of the lower legs is more often caused by polyneuropathy. In cases of total leg and thigh weakness, one first considers a spinal cord disease. Motor neuron disease may begin in the legs, asymmetrically and distally as a rule, and affect them disproportionately to other parts of the body. Thus the differential diagnosis of distal or generalized leg weakness involves more diseases than are involved in the restricted paralyses of other parts of the body.
Isolated quadriceps femoris weakness Isolated quadriceps femoris weakness may be the expression of several diseases. In adults, the most common cause is IBM (where it may be unilateral or asymmetrical) or, a restricted form of Becker muscular dystrophy. In thyrotoxic and steroid myopathies, the major effects are on the quadriceps muscles. If unilateral or bilateral with loss of patellar reflex and sensation over the inner leg, this condition is most often the result of a femoral neuropathy, as occurs from diabetes, or of an upper lumbosacral plexus lesion. Injuries to the hip and knee cause rapid disuse atrophy of the quadriceps muscles. A painful condition of infarction of the muscle on 1 side is seen in diabetic patients.