ALS Medical Classification

Making a proper diagnosis in ALS is complicated because symptoms can vary in each patient. For greater accuracy, physicians have classified every known form.

Classical ALS

A progressive neurological disease characterized by a deterioration of upper (nerve cells leading from the brain to the spinal cord) and lower motor neurons (nerve cells from the spinal cord to muscles). Classical ALS affects more than two-thirds of those with the disease.

Primary Lateral Sclerosis (PLS)

A progressive neurological disease in which the upper motor neurons (nerve cells) deteriorate. If the lower motor neurons are not affected within two years, the disease usually remains a pure upper motor neuron disease. This is the rarest form of ALS.

Progressive Bulbar Palsy (PBP)

An ongoing condition that begins with difficulties in speaking, chewing and swallowing due to lower motor neuron (nerve cells from the spinal cord to muscles) deterioration. This disorder affects about 25 percent of those with ALS.

Progressive Muscular Atrophy (PMA)

A progressive neurological disease in which the lower motor neurons deteriorate. If the upper motor neurons are unaffected within two years, the disease usually remains a pure lower motor neuron disease.

Familial ALS

A progressive neurological disease that affects more than one member of the same family and that’s due to a known gene mutation. This type of ALS accounts for a very small number of people with ALS in the United States (between 5 and 10 percent).