What is the difference between multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS)?

MS has several similarities to ALS (amyotrophic lateral sclerosis) and as such, the two conditions are often confused with one another. But there are some key differences between the two which determine the course of treatment and the affected person’s prognosis.

Some of the similarities between MS and ALS are:

• Both conditions are neurogenerative diseases, meaning they attack and damage the person’s CNS (central nervous system), affecting the muscles and nerves and in turn, impacting an individual’s ability to walk and move around, although MS may affect an individual to a far lesser degree than ALS would.
• Both disorders lead to issues with cognitive impairments and memory and neither of the conditions has a cure.
• ALS and MS both result in the hardening or scarring of the protective sheath of the nerve cells, this is known as sclerosis, however, there are differences that exist in the way that the sclerosis occurs. 
• During the early stages of MS and ALS, the conditions may appear to be similar due to shared symptoms such as muscle spasms, muscle stiffness, fatigue and difficulty walking. But as the individual conditions progress, their differences become more apparent.

Some of the differences between MS and ALS are:

Etiology

MS (multiple sclerosis) is an autoimmune disease that results in the body attacking the protective sheath (myelin sheath) surrounding the nerve cell fibres, affecting the spinal cord and brain.

On the other hand, ALS (amyotrophic lateral sclerosis) is a motor neuron disease (MND) that affects the motor neuron cells of the spinal cord and brain. A motor neuron is a nerve cell that forms a vital part of the pathway that transmits impulses that pass between the spinal cord or brain to a gland or muscle.

What does sclerosis mean?

As previously mentioned, the term ‘sclerosis’ is derived from the Greek word meaning ‘scar’. Both MS and ALS result in scarring and damage to the myelin sheath, however, the difference lies in how this damage occurs.

The nerve cells in the body are covered by thin myelin sheaths that protect the cells and insulate them. Sclerosis that occurs in MS is a result of deterioration in myelin. This breakdown is known as demyelination, and when this occurs, the signs that are sent from the brain to other parts of the body are interfered with and interrupted.

In amyotrophic lateral sclerosis (ALS), sclerosis damages the motor neurons which results in the hardening of the myelin sheath and leads to a loss of motor control and functioning, as well as muscle wasting.

Disease course

MS is an unpredictable condition and will often vary between sufferers with progression rates, specific symptoms and a number of other variables remaining unpredictable even after a diagnosis is made.

ALS is, however, more predictable with the disease following a more definite course of progression.

Late stages

Mobility is mostly affected in a patient during the late stages of multiple sclerosis, however, sufferers are not commonly left completely debilitated. During the later stages of ALS however, the affected person is generally completely paralysed and debilitated.

Affected functions

MS can affect the nerves that control a person’s senses, namely smell, taste, sight and touch. In addition, other areas of the body, such as the bladder may also be affected and the person may also become sensitive to temperature changes.  The emotional and mental health of the sufferer is also greatly influenced.

In contrast, ALS only affects the nerves that are involved in movement. ALS patients tend to experience more physical disabilities whereas MS will typically impact the cognitive abilities more.