Corticosteroid Myopathy

00:00 So now let’s shift gears and talk about steroid myopathy. This is a really important cause of myopathy. It’s common. You’ll see it in patients. It’ll be tested on exams. And it’s something we need to understand because there are some nuances and complexity when evaluating these patients. So let’s break that down over the next few slides. First of all, statin myopathy develops usually several weeks to months after the initiation of steroid use. The typical presentation is what you would expect for a myopathy. There is a proximal pattern of weakness, absence of sensory findings, and normal reflexes. The proximal predominance is a prominent feature and, interestingly, this myopathy presents with a lower extremity pattern of weakness. Patients get weak in their legs, really more so than their arms. They have difficulty rising up out of chairs, difficulty walking upstairs, really with a paucity of arm symptoms. And that pattern should tip you off in a patient who’s on steroids for a steroid myopathy and you can see that here in the diagram. This can occur at any dose of corticosteroids, but we do see a dose dependent effect or a biologic gradient. The higher the dose of the steroids, the more likely this is to occur. There are several forms that we can see.

01:20 There’s an acute form which is extremely uncommon. It’s associated with rhabdomyolysis, but when that’s seen the steroids should be withdrawn rapidly and patients should be supported quickly. The more common form of steroid myopathy and what you’re likely to see is this chronic form, where excessive steroid intake over time at higher doses results in progressive myopathy present in the legs and not as much so in the arms. And again, a key finding with steroid myopathy is this biologic gradient. The higher the dose, the more likely this is to occur. For prednisone, we tend to think that a dose over 20 mg per day starts to be immunosuppressive and a dose higher than 40 really increases the risk of steroid myopathy dramatically. What’s the workup? What do we see? Well, one of the most important things is we don’t see an elevation in CK. And we’ll talk in a minute about how that’s important. EMG and nerve conduction studies are also often performed and the EMG should show myopathic changes; again, short motor units that are short in duration and spontaneous activity which we often see. There’s a lack of increase in CK and this really differs from some of the immune mediated myopathies like polymyositis and dermatomyositis. And this is a common clinical scenario. A patient has poly- or dermatomyositis or necrotizing myopathy and is put on prednisone. They’re put on high doses of prednisone for a long period of time and they improve. And then gradually over the course of several months, they get worse again. We check the CK and if the CK is elevated, their disease, their immune-mediated myopathy must be worsening. If we check the CK and it’s normal, then we worry that the myopathy may be from the steroids and not from the underlying immune condition. So what’s the management? Well, we’re going to stop the steroids. And sometimes they need to be tapered or tapered rapidly, and the ultimate goal is to stop the steroids. For as long as the steroids were on board, it will take even longer for the muscle weakness to improve after their discontinuation. And the second most important management for these patients is aggressive physical therapy. Withdrawal of the steroids will prevent further muscle damage, but in order to get the patient stronger, they've got to move and aggressive physical therapy is of critical importance for these patients.