1Romagna E.Incidence of myasthenia gravis in the Emilia-Romagna region:a prospective multicenter study.Neurology,1998,51:225-258.
2Aragones JM,Bolibar I,Bonfill X,et al.Myasthenia gravis:a higher than expected incidence in the elderly.Neurology,2003,60:1026-1029.
3Gourie-Devi M,Nalini A,Sandhya S.Early or late appearance of "dropped head syndrome"in amyotrophic lateral sclerosis.J Neurol Neurosurg Psychiatry,2003,74:683-686.
4Goh KJ,Wong KT,Tan CT.Myopathic dropped head syndrome:a syndrome of mixed etiology.J Clin Neurosci,2000,7:334-336.
