1. Epidemiology.- 2. Natural History.- 3. Novel Classifications in HFS.- 4. Pathogenesis.- 5. Clinical Diagnosis.- 6. Electrophysiological Diagnosis.- 7. Radiological Diagnosis.- 8. Differential Diagnosis.- 9. Surgical Principles.- 10. Technical Difficulties.- 11. Intraoperative Monitoring.- 12. Anesthesia.- 13. Medical Treatment.- 14. Botulinum Toxin Injection.- 15. Complications.- 16. Prognosis.- 17. Redo Surgery.