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Symptoms and Signs of Dementia in ALS

Doctor's Notes on Dementia in Amyotrophic Lateral Sclerosis (Lou Gehrig's Disease)

Amyotrophic lateral sclerosis (ALS, also called Lou Gehrig's disease) is a type of motor neuron disorder that affects the part of the nervous system that controls voluntary movements. The muscles become progressively weaker, and the disease eventually leads to paralysis and death. In most people with ALS cognitive processes (such as thinking, learning, memory, and speech) are not affected. Occasionally, a person with ALS does experience dementia, a severe brain disorder that interferes with a person’s ability to carry out everyday activities.

Symptoms of dementia in amyotrophic lateral sclerosis (Lou Gehrig disease) include apathy (lack of interest, withdrawal), lack of emotion, reduced spontaneity, loss of inhibition, restlessness or overactivity, social inappropriateness, mood swings, memory loss, loss of speech and/or language (partial or complete), or loss of reasoning or problem-solving ability.

Medical Author: John P. Cunha, DO, FACOEP
Medically Reviewed on 3/11/2019

Dementia in Amyotrophic Lateral Sclerosis (Lou Gehrig's Disease) Symptoms

Frontal lobe dementia in ALS usually appears as a change in personality and behavior. The exact nature of this change varies from person to person. The following symptoms are common:

  • Apathy (lack of interest, withdrawal)
  • Lack of emotion
  • Reduced spontaneity
  • Loss of inhibition
  • Restlessness or overactivity
  • Social inappropriateness
  • Mood swings

Cognitive symptoms include the following:

  • Memory loss
  • Loss of speech and/or language, partial or complete
  • Loss of reasoning or problem-solving ability

Some individuals develop repetitive rituals involving hoarding, dressing, wandering, or using the bathroom. Others may overeat or develop strange eating rituals.

The cognitive changes often precede symptoms of ALS. Throughout the course of the dementia, the following typical signs and symptoms of ALS also progress:

  • Limb weakness
  • Swallowing problems
  • Muscle wasting (atrophy)
  • Muscle twitches (fasciculations)
  • Shortness of breath

Dementia in Amyotrophic Lateral Sclerosis (Lou Gehrig's Disease) Causes

We do not know what causes frontal lobe dementia in people with ALS. A few people have a family history of this type of dementia, but we do not understand the connection between this dementia and ALS. More than one cause may be involved.

Dementia, Alzheimer's Disease, and Aging Brains Slideshow

Dementia, Alzheimer's Disease, and Aging Brains Slideshow

In 1906 Auguste Deter, a woman in her early 50s, became the first person diagnosed with Alzheimer's disease, a form of dementia. The disease is named after the doctor who first described it, Alois Alzheimer. The disease is characterized by odd behavior, memory problems, paranoia, disorientation, agitation, and delusions. After Deter’s death, Alzheimer performed a brain autopsy and discovered dramatic shrinkage and abnormal deposits in and around nerve cells.

In 1910 the term “Alzheimer’s Disease” was formally used. In 1974 Congress established the National Institute on Aging (NIA), the primary federal agency supporting Alzheimer’s research.


Kasper, D.L., et al., eds. Harrison's Principles of Internal Medicine, 19th Ed. United States: McGraw-Hill Education, 2015.