Head and neck surgery causes speech changes by affecting the structures, muscles, and nerves essential for voice and speech production. Surgery may affect or remove parts of the tongue, larynx, throat, or facial muscles needed for clear articulation and voice control. Post-surgical swelling, scar tissue and nerve damage further reduce mobility, coordination, and normal airflow patterns required for speech. The severity depends on the surgical site and extent of tissue affected, but speech therapy can help patients adapt and improve their communication abilities.