The plan for any movement originates in the brain. The major part of the brain involved in the initiation and control of voluntary movement is the primary motor cortex. Motor neurons in the brain are called upper motor neurons (UMNs), whereas motor neurons in the brain stem and spinal cord are called lower motor neurons (LMNs). UMNs are unable to leave the CNS; therefore they must synapse with LMNs whose axons can leave the CNS, which allows them to synapse with muscles throughout the body. Thus, in a normal situation, messages from UMNs are transferred to LMNs, and from there are transferred to specific muscles. UMNs and LMNs are responsible for movements such as walking and chewing, and movement of the arms, legs, chest, and face, respectively. This permits healthy individuals the ability to voluntarily move their muscles with ease.
Amyotrophic Lateral Sclerosis is also referred to as a motor neuron disorder (MND), as it is characterized by the continual degeneration of upper and lower motor neurons. These motor neurons, as previously stated, are responsible for voluntary muscles in the body, and as the neurons degenerate, or die, the neurons are unable to send messages to the muscles. When muscles can no longer receive signals, they become unable to function, and in turn, weaken and waste away. Eventually, the brain loses its ability to start and control voluntary movement, resulting in paralysis.
Since ALS only affects the voluntary motor neurons, the senses (seeing, smelling, tasting, hearing, and tactile sensations) are spared. The involuntary motor neurons are also not affected (for example, the heart and digestive system). Additionally, the individual is often not affected cognitively.
Two major forms of ALS exist: familial and sporadic. Familial is the lesser common of the two, accounting for only 5-10% of cases. The majority of cases (90-95%) are of the sporadic form. When ALS occurs in a family line more than once, it is considered familial ALS. In this case, ALS is a genetically transmitted, and most often has an autosomal-dominant pattern of inheritance. Where familial ALS is genetically transferred, sporadic ALS may affect any one person at any given time (Niebauer & Roth-Kauffman, 2012).
About 75% of ALS patients have limb onset ALS, while the other 25% have bulbar onset ALS. The symptoms of limb onset ALS are first noticed in either of the limbs, and include weakness, twitching (fasciculations), and cramps, and in the later stages, spasms. Whether the weakness began in the arms or the legs, it eventually spreads to the contrasting limbs. Additionally, most patients with limb onset ALS eventually develop bulbar and respiratory symptoms (Wijesekera & Leigh, 2009).
Symptoms of bulbar onset ALS often begin with dysarthria of speech, or difficulty speaking due to weakening of the muscles that aid in speaking. Other symptoms include sialorrhoea, or excessive...