WORKUP	Section 5 of 10
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Lab Studies:

• Chronic (classic) steroid myopathy

• Serum levels of creatinine kinase typically are within the reference range.

• Creatinine excretion in the urine increases dramatically and can precede the clinical appearance of myopathy by several days.

• Myoglobinuria and rhabdomyolysis are absent.

• Acute steroid myopathy: In most cases, high levels of serum creatine kinase are found, as well as associated myoglobinuria.

Other Tests:

• Muscle biopsy in chronic (classic) steroid myopathy

• Muscle biopsy shows preferential atrophy of type II fibers, particularly the fast-twitch glycolytic fibers (type IIB).

• Some atrophy of other type II fibers and, to a small degree, type I muscle fibers can occur.

• Increased variation in diameter of muscle fibers occurs.

• Lack of evidence of muscle fiber inflammation is reported.

• A distinct lack of necrosis or regeneration of muscle is present.

• Less active muscles appear to be affected preferentially.

• Muscle biopsy in acute steroid myopathy: Muscle biopsy shows focal and diffuse necrosis of all fiber types, without predilection for type II fibers.

• Electromyography (EMG) and nerve conduction studies (NCSs) in chronic (classic) steroid myopathy

• Motor and sensory NCS results typically are normal.

• Repetitive stimulation studies do not reveal significant decrement or increment.

• EMG studies reveal normal insertional activity with little abnormal spontaneous activity (positive sharp waves and fibrillation potentials).

• EMG may reveal mild decrease in motor unit action potential amplitude during maximal recruitment.

• In moderate-to-severe cases, studies may show an early recruitment pattern.

• EMG and NCS in acute steroid myopathy: Some case reports have indicated abnormal EMG findings, including abnormal spontaneous activity (positive sharp waves and fibrillation potentials), small polyphasic motor units, and early recruitment, as well as findings suggestive of associated neuropathy following high-dose corticosteroid treatment.

	TREATMENT	Section 6 of 10
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Rehabilitation Program:

• Physical Therapy: Some literature suggests that aerobic exercises and resistance training may help prevent or reduce severity of weakness. Although there are no definitive recommendations regarding therapy for steroid myopathy, it would seem reasonable to direct therapy to address the weakness and resulting impaired mobility. Range-of-motion exercises, either passive, active-assisted, or active, depending on degree of weakness, and stretching exercises should be performed to prevent joint contractures. As a general rule, resistance exercises should be limited to muscles with greater than antigravity strength. Bed mobility, balance activities, transfer training, and gait training should be included to address decreased mobility.

• Occupational Therapy: Occupational therapy may focus on maximizing independence for performance of activities of daily living. Training may include the use of assistive devices to enhance the patient's ability to perform self-care tasks, such as a balanced forearm orthosis to allow positioning of the upper arm to allow for more independent feeding. Other adaptive equipment may include a raised toilet seat and similar equipment that allow easier standing from sitting and/or a motorized lift for ascending stairs.

Consultations: Any adjustments of the patient's corticosteroid medications should be coordinated with the physician who has been prescribing those medications for the patient. Given reports of respiratory muscle weakness causing respiratory impairments, consider consultation with a pulmonologist. Consultation with a neurologist can be considered for assisting with diagnosis and for excluding other potential causes of weakness. Consultation with a physiatrist can also be included for assistance with diagnosis and management of a therapy program.

Other Treatment (injection, manipulation, etc.):

• In cases of myopathy due to long-term corticosteroid use, decreasing the corticosteroid dose below a threshold of 30 mg/d may result in resolution of muscle weakness. In cases due to a short course of high-dose corticosteroid use, partial or complete recovery has been reported following discontinuation of steroid administration.

	MEDICATION	Section 7 of 10
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Various medications, including potassium supplements, phenytoin, vitamin E, and anabolic steroids, have been tried as potential treatments for steroid myopathy. None have been shown clearly to demonstrate prevention or reversal of the muscle weakness induced by steroid myopathy. The main treatment recommendations are to decrease the dose of steroid to below a threshold level or to discontinue use of the corticosteroid. Alternate-day dosing could also be considered. Another recommendation is to change the steroid used to one that is not fluorinated.

	MISCELLANEOUS	Section 9 of 10
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Medical/Legal Pitfalls:

• The main potential pitfall in diagnosing steroid myopathy is in patients with polymyositis/dermatomyositis, which typically is treated with corticosteroids. The main symptom of polymyositis/dermatomyositis is proximal upper and lower extremity weakness. When these patients, while treated on corticosteroids, develop increasing weakness, it can be difficult to determine whether the weakness is secondary to the polymyositis or to steroid myopathy.

• Laboratory studies can aid in differentiating between the two. Creatine kinase typically is elevated significantly in polymyositis/dermatomyositis. In steroid myopathy, it typically has been described that, although there is elevated urinary creatinine excretion, the serum creatine kinase is not elevated significantly. However, some studies have reported elevations of creatine kinase in some cases of the previously described acute form of steroid myopathy.

• On electrodiagnostic study, polymyositis typically demonstrates normal NCS results, as also is found typically with steroid myopathy. However, on EMG study, polymyositis demonstrates abnormal spontaneous activity and increased polyphasic waveforms with short durations. The classic form of steroid myopathy has been described as not demonstrating significant abnormal EMG findings. Again, some studies have described an acute form of steroid myopathy that can demonstrate abnormal spontaneous activity, small polyphasic waveforms, and early recruitment pattern.

• Initial recommendation is to decrease or discontinue the use of the corticosteroid. If the weakness improves, then steroid myopathy is the most likely diagnosis. If the weakness persists or worsens, then the most likely diagnosis is worsening of the polymyositis.