title: Amyotrophic lateral sclerosis mimic syndromes: a population-based study.
abstract: BACKGROUND
  The Irish ALS Register is a population-based register of the epidemiological characteristics of amyotrophic lateral sclerosis (ALS) in the republic of Ireland.
  
  
  OBJECTIVE
  To describe the clinical and demographic details of those patients included in the Irish ALS Register who were incorrectly diagnosed as having ALS (patients who were ultimately rediagnosed as having an "ALS mimic syndrome").
  
  
  METHODS
  The medical records of each patient referred to the register are routinely reviewed and, where possible, patients are examined by our group during their illness.
  
  
  RESULTS
  Between January 1, 1993, and December 31, 1997, 32 patients (representing 7.3% of 437 referrals) were rediagnosed as having a condition other than ALS. The median age at onset for these 32 patients was 56.0 years (range, 19.5-85.8 years) for men and 53.5 years (range, 39.5-70.4 years) for women. Twenty-nine patients (91%) presented with symptoms referable to the limbs, and the remainder presented with symptoms involving the bulbar musculature. Multifocal motor neuropathy was the most common condition mistaken for ALS, accounting for 7 cases (22%), followed closely by Kennedy disease (4 cases [13%]). Factors leading to diagnostic revision included evolution of atypical symptoms, results of specific investigations, and failure of symptoms to progress. Twenty-seven (84%) of the patients with an ALS mimic syndrome fulfilled the El Escorial criteria for either "suspected" or "possible" ALS, 4 (13%) met the criteria for probable ALS, and 1 (3%) had definite ALS.
  
  
  CONCLUSIONS
  The application of the El Escorial diagnostic criteria may facilitate early recognition of non-ALS cases. Misdiagnosis of ALS remains a common clinical problem despite the increased availability of investigations and a greater awareness among neurologists of potential diagnostic pitfalls.
authors.affiliation: Department of Neurology, Beaumont Hospital, Dublin, Ireland.
authors.forename: B J
authors.initials: BJ
authors.lastname: Traynor
authors.forename: M B
authors.initials: MB
authors.lastname: Codd
authors.forename: B
authors.initials: B
authors.lastname: Corr
authors.forename: C
authors.initials: C
authors.lastname: Forde
authors.forename: E
authors.initials: E
authors.lastname: Frost
authors.forename: O
authors.initials: O
authors.lastname: Hardiman
mesh_terms: D000328:Adult; D017668:Age of Onset; D000368:Aged; D000369:Aged, 80 and over; D000690:Amyotrophic Lateral Sclerosis / Q000175:diagnosis* / Q000453:epidemiology*; D002493:Central Nervous System Diseases / Q000175:diagnosis; D003937:Diagnosis, Differential; D005260:Female; D006801:Humans; D007494:Ireland / Q000453:epidemiology; D008297:Male; D008875:Middle Aged; D012042:Registries / Q000706:statistics & numerical data*