The dropped head sign in parkinsonism.

We describe seven patients who exhibited the dropped head sign in parkinsonism. These included six females and one male between the ages of 53 and 74. Three patients were clinically diagnosed as probable Parkinson's disease and four were diagnosed with probable multiple system atrophy. None had weakness in the posterior neck muscles or spasms in the anterior neck muscles. When the patients attempted to extend the head voluntarily or passively muscle contraction that was not seen in the dropped-head condition appeared. Surface electromyography of the neck indicated that the anterior neck muscles had rigidity. A gamma-block of the SCM muscles reduced the muscle activity when the head was elevated and improved the dropped-head condition slightly. These findings seem to indicate that the dropped head sign in parkinsonism could be associated with anterior neck muscle rigidity. Although the severity of the dropped head condition was affected by medication or by the clinical course in three patients, there was no clear relationship between the severity of the dropped head condition and the parkinsonism. We suspected that unbalanced muscle rigidity between the anterior and the posterior neck muscles could cause the dropped head sign.