Table 1.

Revised El Escorial criteria for clinical diagnosis of ALS (Brooks et al, 2000).

Clinical Grade	Description
Clinically Definite ALS	Clinical evidence of UMN, as well as LMN signs, in three regions.
Clinically Probable ALS	Clinical evidence of UMN and LMN signs in at least two regions with some UMN signs necessarily rostral to (above) the LMN signs.
Clinically Probable - Laboratory-Supported ALS	Clinical signs of UMN and LMN dysfunction in only one region, or UMN signs in one region, and LMN signs defined by EMG criteria in at least two limbs, with neuroimaging and clinical laboratory investigations to exclude other causes.
Clinically Possible ALS	Clinical signs of both UMN and LMN dysfunction in only one region or UMN signs alone in two or more regions; or LMN signs 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 be excluded to accept a diagnosis of Clinically possible ALS.
Clinically Suspected ALS	Is a pure LMN syndrome, where the diagnosis of ALS could not be regarded as sufficiently certain to include the patient in a research study.

^*The body is divided into four regions: cranial, cervical, thoracic and lumbosacral.