**1. Introduction**

There are several synonyms for Amyotrophic Lateral Sclerosis (ALS) which include Motor Neuron Disease (MND), Charcot's disease, and Lou Gehrig's disease. The latter is named after the American baseball professional Lou Gehrig, who died of ALS in the 1940s (Miller, 2011).

The symptoms of motor neuron disease (MND) have first been described by several neurologists by the mid-19th century. The French neurologist Charcot defined the nosological entity "amyotrophic lateral sclerosis" (ALS) some years later (historic aspects of ALS are reviewed in (Eisen, 2007; Mitsumoto et al., 2006; Oliveira & Pereira, 2009; Rowland, 2001; Wijesekera & Leigh, 2009)).

In the present understanding, MND comprehends a spectrum of different neurodegenerative syndromes which show a common neuropathology, i. e. the progressive degeneration of motor neurons.

These syndromes include the "classical" ALS, progressive bulbar palsy (PBP), progressive muscular atrophy (PMA), primary lateral sclerosis (PLS), flail arm syndrome (Vulpian-Bernhardt syndrome), flail leg syndrome, and ALS with multi-system involvement (e.g., Fronto-Temporal Dementia, FTD) (**Fig. 1**) (reviewed in Lillo & Hodges, 2009; Silani et al., 2011).
