Acoustic reflex abnormalities in cranial-cervical dystonia.

Previous anatomic and physiologic studies suggest brainstem dysfunction in cranial-cervical dystonia. To further explore this, we studied suprathreshold acoustic reflex waveforms in 15 such patients. A unique feature of this technique is its ability to reject movement artifacts before averaging the acoustic reflex waveforms. Thirteen patients (87%) showed some abnormality in reflex waveform morphology. There were both amplitude and latency abnormalities. These findings support the hypothesis that cranial-cervical dystonia reflects dysfunction of the brainstem.