Reflexes are symmetric and normal. No ataxia is noted. The patient has good hand grip strength, but is unable to get out of a chair without assistance. This patient's presentation is consistent with a toxic myopathy. As in this case, there is usually diffuse and symmetric involvement.
Myopathic weakness is noted more in the proximal muscles and sensory findings are lacking.
Deep tendon reflexes are preserved until the myopathy is quite advanced. Lithium is one etiology of myopathy. Another cause of myopathy is hypokalemia. Hypokalemia due to diuretic use or chronic inhalant exposure has been noted to cause this type of myopathy. Abuse of licorice, which contains glycyrrhizic acid, can also cause such a myopathy by its aldosterone-like effect and associated hypokalemia.