**3. Measuring the disease**

The use of ALS assessment techniques such as rating scales is to monitor disease progression , to make outcome parameters in clinical trials comparable; and to predict efficacy of therapeutic strategies (Cudkowicz et al., 2004).

Typical ALS assessment techniques comprehend (i) global scales which are based on clinical observation, (ii) measuring of the muscular strength, (iii) electrophysiological testing, and (iv) the assessment of the quality of life.

### **3.1 Clinical assessment scales**

Global scales subsume (i) scores based on subjective or historic data, such as the ALS functional rating scale (ALSFRS) (Cedarbaum & Stambler, 1997; The ALS CNTF treatment study (ACTS) phase I-II Study Group, 1996), and the ALS severity scale (ALSSS) (Hillel et al., 1989), (ii) scores based on clinical tests such as the Norris scale (Norris et al., 1974), or the Appel scale (Appel et al., 1987), and (iii) scales used both for ALS and other diseases such as the Schwab and England global rating scale (Schwab & England, 1969), or the modified Ashworth spasticity scale (Bohannon & Smith, 1987).

### **3.2 Muscular function testing**

Measuring of the muscular strength includes quantitative tests, maximum voluntary isometric contraction, handheld dynamometry, Jamar grip strength, manual muscle testing. Moreover, the spirometric measurement of the forced vital capacity and maximum voluntary ventilation can also be included in muscle tests.

### **3.3 Electrophysiological measurements**

Electrophysiological testing includes compound muscle action potentials (CMAPs) and motor unit number estimate (MUNE) (Shefner et al., 2011) or the motor unit number index (MUNIX) (Nandedkar et al., 2010; Neuwirth et al., 2011).

A consensus conference has defined electrophysiological criteria for the diagnosis of ALS (de Carvalho et al., 2008).
