Underappreciated Statin-Induced Myopathic Weakness Causes Disability
Bruce H. Dobkin
University of California Los Angeles, Reed Neurologic Research Center,
bdob...@mednet.ucla.edu

Introduction. Myopathic syndromes induced by 3-hydroxy-3-methylglutaryl

coenzyme A (HMG-CoA) reductase inhibitors (statins) include muscle
complaints, myalgia, myositis, and rhabdomyolysis. No prospective study

of statins, however, included tests of strength, so the incidence of
weakness, with or without muscle symptoms and elevated enzymes, is
unknown, and perhaps overlooked. Methods. From a convenience sample of
patients referred to an outpatient neurorehabilitation clinic over the
course of 1 year, 8 patients with hemiparetic stroke and 10 patients
with other presumed neurologic diseases presented with new difficulty
walking by 3 to 12 months after starting one of 3 statins. They
reported no myalgias, exercise-induced aches, or weakness. Examination
revealed proximal paresis graded 4/5 on the unaffected side in the
hemiparetic patients and symmetrical bilateral proximal limb and neck
flexor weakness graded 4/5 in the others. They stood up with difficulty

and walked with bilateral hip drop and imbalance on turns. Results.
Laboratory tests did not reveal myositis or other causes for paresis.
No improvement in strength or mobility was found 6 weeks after
initiating resistance exercises. The statin agent was stopped. By 3
months off statin, all recovered 5/5 proximal strength. Walking
improved, and they arose from a chair without pushing off with their
arms. Discussion. Serial manual muscle testing after initiating a
statin may detect a reversible cause of disability. A genetic
predisposition to statin-induced myopathic proximal weakness with
normal creatine kinase is consistent with a continuum of previously
reported symptoms and signs but may be underappreciated.

(in the discussion, the author notes that while single-subject,
double-blinded statins vs placebo studies would make the causal
relationship between disabling myopathy more apparent, he notes
recurrences in his patients' symptoms when the investigator was unaware

that several of the subjects had been placed back on the statin by
their primary physicians. p. 261)