Myotonic potentials in statin-induced rhabdomyolysis

Abstract

Lipid lowering drugs are used worldwide to control dyslipidemias. The muscle disorder associated with them are coined cholesterol-lowering agents myopathy (CLAM) 1 . The annual incidence of rhabdomyolysis in patients taking statins is 3.4 per 100000 persons 2 . Between 1987 and 2001 there were 42 deaths +related to statin-induced rhabdomyolysis, resulting in a mortality rate of 0.15 per million of prescriptions 3 . Although myotonic potentials have been described in some drug-related myopathies, they are rarely reported in CLAM. Though there are a few experimental myotonic myopathy associated with statin in rabbits 4-6 , there was only one single report describing 5 patients with this finding in humans 7 .We report a patient with statin-related rhabdomyolysis and profuse myotonic potentials in the needle EMG with clinical and electrophysiological recovery shortly after the statin interruption. CaSeA 68 year-old Asian Brazilian woman was admitted with progressive painless weakness for one week, started on the proximal muscles of the four limbs and neck flexors with rapid progression to inability to walk and elevate the limbs. Urine was redbrown in color. Thirty days before the admission she was put on simvastatin due to hypercholesterolemia. Other medication she was taking was enalapril for mild hypertension. There was no personal or family history of myopathy. On neurological examination, abnormal findings were grade 2 (MRC) strength in the proximal lower limb muscles and grade 3 in the proximal upper limb muscles, grade 4 in the distal muscles and hypoactive deep tendon reflexes. No clinical myotonia was detected.A complete blood count, electrolytes, creatinine, glucose, TSH, and free T4 were all normals. Myoglobin was detected in the urine. CPK was 22.260 U/l on the admission day and 55.000 U/l on the third day. AST and ALT were 790 and 750 U/l, respectively. The nerve conduction studies perfomed in both arms and legs showed normal results in the median, ulnar, superficial radial, tibial, peroneal, superficial peroneal and sural nerves bilaterally. The F wave latencies were normal in the median, ulnar, fibular and tibial nerves bilaterally. The needle EMG perfomed with disposable monopolar needle in cervical paraspinal, supraspinatus, deltoid, triceps, abdutor pollicis brevis and first dorsal interosseus in the upper right limb and tibialis anterior, gastrocnemius, vastus lateralis and iliopsoas in the right lower limb showed rare positive sharp waves and fibrillations in the right supraspinatus muscle, as well as a few small amplitude and short duration (SASD) motor unit potentials (MUP) in the right iliopsoas muscle. On the other hand, the needle study showed profuse amount of myotonic potentials in deltoid, supraspinatus, iliopsoas and cervical paraspinal muscles on the right side (Fig 1).Simvastatin was stopped and vigorous hydration was started to prevent acute renal failure. She was discharged two weeks later with normal strength, renal function and CPK levels. A second needle EMG performed 30 days after...

Diagnostic modelling and therapeutic monitoring of immune-mediated necrotizing myopathy: role of electrical myotonia

“…Because we found statin exposure was most commonly linked to electrical myotonia, this is likely a pathological clue with membrane channel dysfunction, secondary to membrane over-expression of HMGCR or channel dysfunction following an immune response. Previous smaller studies have also provided similar inference ( Meriggioli et al , 2001 ; de Almeida et al , 2008 ; Kassardjian et al , 2015 b ). The administration of simvastatin to rabbits has been shown to produce myotonic discharges in association with elevated CK and necrotic, and/or degenerative muscle fibres on biopsy ( Nakahara et al , 1992 ).…”

Primary Hyperparathyroidism and Hyperthyroidism in a Patient with Myotonic Dystrophy: A Case Report and Review of the Literature

“…Then, it may be hard to distinguish them from myotonia related to MD in the absence of electromyographic study. These myotonic discharges are nonspecific and can be experienced in other various diseases such as Duchenne muscular dystrophy, hypokalemic periodic paralysis, drug induced myotonia, and thyrotoxicosis [ 34 – 36 ]. Our patient had a family history of MD, cataracts, and cardiac disorders and she continued to show clinical evidence of myotonia 2 years after successful medical treatment with benzylthiouracil.…”

Electromyographic and histological features of postpartum hypernatremic rhabdomyolysis

“…[5] Fibrillations positive sharp waves, myopathic potentials and myotonic discharges were demonstrated in patients experiencing statin-induced rhabdomyolysis. [67]…”

“…[2456] Some patients with statin-induced myopathy had myotonic discharges. [67] Among the acquired metabolic causes, hypernatremia is a rare cause for rhabdomyolysis. [138910] To the best of our knowledge, electromyographic findings in patients with hypernatremic rhabdomyolysis have not been reported.…”