Dropped head presentation of mitochondrial myopathy.

Dropped head secondary to weakness of the neck extensors has been reported in a wide assortment of neuromuscular disorders. Infrequently, dropped head can be the first sign of disease. We describe two patients with dropped head as the presenting manifestation of mitochondrial myopathy. In both patients, serum lactate was elevated and muscle biopsy showed mitochondrial proliferation. Mitochondrial myopathy should be considered in the differential diagnosis of dropped head syndrome, particularly when other, more common causes such as myasthenia gravis, polymyositis, and amyotrophic lateral sclerosis have been excluded by appropriate laboratory and electrophysiological studies.