ReferencesDanek A. Geniospasm: hereditary chin trembling. Mov Disord 1993;8:335-8. Laurance BM, Matthews WB, Diggle JH. Hereditary quivering of the chin. Arch Dis Child 1968;43:249-51. Alsager DE, Bowen P, Bamforth JS. Trembling chin-a report of this inheritable dominant character in a fourgeneration Canadian family. Clin Genet 1991 ;40: 186-9. Gordon K, Cadera W, Hinton G . Successful treatment of hereditary trembling chin with botulinum toxin. J Child Neurol 1993;8: 154-6. Grossman BJ. Trembling of the chin: an inheritable dominant character. Pediatrics 1957; 19:453-5. Johnson LF, Kinsbourne M, Renuart AW. Hereditary chintrembling with nocturnal myoclonus and tongue-biting in dizygous twins. Dev Med Child Neurol 1971;13:72&9. Wadlington WB. Familial trembling of the chin. J Pediatr 19% ;53 : 3 162 1. Rosenberg ML, Clark JB. Familial trembling of the chin. Neurology 1987;37(suppl 1 ) : 190. Blaw ME, Leroy RF, Steinberg JB, Herman J. Hereditary quivering chin and REM behavioral disorder. Ann Neurol 1989;26:471. Stocks P. Facial spasm inherited through four generations. Biometrika 1922123; 14:3 1 1-5. Goldsmith JB. The inheritance of "facial spasm." J Hered 1927; 18: 185-7. Biary N, Koller WC. Essential tongue tremor. Mov Disord 1987;2:25-9. Rapoport A, Lampel Y, Sarova I. Clinical and epidemiological features of essential tremor of the jaw. Mov Disord 1991 ; 6:276. Koller WC, Glatt S, Biary N, Rubino FA. Essential tremor variants: effect of treatment. Clin Neuropharmacol 1987;4: Bain PG, Findley LJ, Thompson PD, et al. A study of hereditary essential tremor. Brain 1994;117:805-34. Jedynak CP, Bonnet AM, Agid Y. Tremor and idiopathic dystonia. Mov Disord 1991 ;6:230-6. Elble RJ, Moody C, Higgins C. Primary writing tremor. A form of focal dystonia? Mov Disord 1990;5: 118-26. Rivest J, Marsden CD. Trunk and head tremor as isolated Videotape segments accompany this article.