What are the different forms of ALS?

There are two main forms of ALS. They represent the clinical onsets:

Spinal form

The spinal form, which represents two-thirds of cases, generally begins with muscles weakness accompanied by small involuntary muscle contractions or twitches. These are dues to the degeneration of motor neurons in the spinal cord.

Bulbar form

For some people, the muscles used to speak, swallow and/or breathe are the first to be affected. This is referred to as bulbar ALS. However, since the disease tends to evolve in various areas at once, the distinction between these two forms is not always evident at the time of diagnosis.

There are also two forms of ALS:

  • Sporadic ALS
  • Familial ALS

The most common form of ALS is called sporadic ALS, which means that no one in the patient’s immediate and extended family has been affected by the disease.

Conversely, familial ALS is hereditary and affects several members of the same family. Although both forms of the disease are identical, familial ALS represents only 5 to 10% of all cases.

In some ALS literature, two other rare forms of ALS are reported:

  • Juvenile ALS
  • Primary Lateral Sclerosis(PLS)

Juvenile ALS is an extremely rare form of ALS that affects children. As for primary lateral sclerosis, experts believe it is a continuum of ALS and not a distinct affliction. It is considered a more benign expression of ALS, with a very slow progression. PLS may progress over decades and the expected lifespan of a person with PLS may be normal.Some people diagnosed with PLS, at first, may end up getting an ALS diagnosis after a few years if muscle wasting symptoms also occur.

Find out more about Primary Lateral Sclerosis.

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