Posted in Web Understanding Spasmodic Dysphonia – THE VOICE FOUNDATION January 29, 2025 What is spasmodic dysphonia (SD)? Spasmodic dysphonia (SD) is a voice disorder in which abrupt, involuntary movements (spasms) in the voice box cause abnormal voice (dysphonia). https://voicefoundation.org/health-science/voice-disorders/voice-disorders/spasmodic-dysphonia/understanding-spasmodic-dysphonia/