[Two cases with dropped head syndrome caused by hypokalemic myopathy].

ABSTRACT

We reported two women (78 and 85 years of age) with dropped head syndrome caused by hypokalemic myopathy restricted to the posterior cervical muscles. Both presented with relatively rapid onset of severe neck extensor weakness. Needle EMG demonstrated myogenic changes in the cervical paraspinal muscles and there were high intensity signals in the posterior cervical muscles on the neck MRI. Dropped head syndrome resolved in both patients as potassium normalized. One of the patients relapsed 11 months later with recurrent hypokalemia, but recovered rapidly with supplementation of potassium. Focal myopathy localized in the posterior cervical muscles due to hypokalemia should be considered as one of the possible causes of dropped head syndrome.