Unifying Concepts

El Escorial Criteria for the Diagnosis of Amyotrophic Lateral Sclerosis (ALS)

The diagnosis of Amyotrophic Lateral Sclerosis (ALS) requires

A. the presence of:
(A:1) evidence of lower motor neuron (LMN) degeneration by clinical, electrophysiological or neuropathologic examination,
(A:2) evidence of upper motor neuron (UMN) degeneration by clinical examination, and
(A:3) progressive spread of symptoms or signs within a region or to other regions, as determined by history or examination, together with

B. the absence of:
(B:1) electrophysiological and pathological evidence of other disease processes that might explain the signs of LMN and/or UMN degeneration, and
(B:2) neuroimaging evidence of other disease processes that might explain the observed clinical and electrophysiological signs.

Diagnostic Categories

  1. Clinically Definite ALS: is defined on clinical evidence alone by the presence of UMN, as well as LMN signs, in three regions.
  2. Clinically Probable ALS: is defined on clinical evidence alone by UMN and LMN signs in at least two regions with some UMN signs necessarily rostral to (above) the LMN signs.
    The terms Clinically Probable ALS – Laboratory-supported and Clinically Possible ALS are used to describe these categories of clinical certainty on clinical and criteria or only clinical criteria:
  3. Clinically Probable – Laboratory-supported ALS: is defined when clinical signs of UMN and LMN dysfunction are in only one region, or when UMN signs alone are present in one region, and LMN signs defined by EMG criteria are present in at least two limbs, with proper application of neuroimaging and clinical laboratory protocols to exclude other causes.
  4. Clinically Possible ALS: is defined when clinical signs of UMN and LMN dysfunction are found together in only one region or UMN signs are found alone in two or more regions; or LMN signs are found rostral to UMN signs and the diagnosis of Clinically Probable – Laboratory-supported ALS cannot be proven by evidence on clinical grounds in conjunction with electrodiagnostic, neurophysiologic, neuroimaging or clinical laboratory studies. Other diagnoses must have been excluded to accept a diagnosis of Clinically possible ALS.
  5. Clinically Suspected ALS: it is a pure LMN syndrome, wherein the diagnosis of ALS could not be regarded as sufficiently certain to include the patient in a research study. Hence, this category is deleted from the revised El Escorial Criteria for the Diagnosis of ALS.



  1. Brooks BR. El Escorial World Federation of Neurology criteria for the diagnosis of amyotrophic lateral sclerosis. Subcommittee on Motor Neuron Diseases/Amyotrophic Lateral Sclerosis of the World Federation of Neurology Research Group on Neuromuscular Diseases and the El Escorial “Clinical limits of amyotrophic lateral sclerosis” workshop contributors. J Neurol Sci. 1994 Jul;124 Suppl:96-107. [Medline]
  2. Mitsumoto H. Diagnosis and progression of ALS. Neurology 1997; 48(S4):2S-8S.
  3. Ross MA, Miller RG, Berchert L, Parry G, Barohn RJ, Armon C, Bryan WW, Petajan J, Stromatt S, Goodpasture J, McGuire D. Toward earlier diagnosis of amyotrophic lateral sclerosis: revised criteria. rhCNTF ALS Study Group. Neurology. 1998 Mar;50(3):768-72. [Medline]


Created: Jul 13, 2008

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