Up to half of people with ALS also struggle with mental decline, and up to 15 percent have dementia. Here’s what you should know.
ALS is often characterized as a disease that ravages the body but leaves the mind relatively intact. Look no further for evidence than its longest-lived survivor, theoretical physicist, Stephen Hawking. Since his diagnosis in 1963, Hawking has taught mathematics at Cambridge University, lectured around the world, and written several books — including the bestselling “A Brief History of Time.”
Yet not everyone with ALS is left intellectually unscathed. Although the loss of movement remains the hallmark symptom of ALS, 8 percent to 15 percent of people with this condition also have dementia. Many more exhibit milder problems with thinking, language, and behavior that do not significantly affect daily life.
Researchers have revised their perception that ALS is solely a movement-based disease, and are now recognizing it as a multisystem disorder that damages brain regions critical to both movement and thinking.
The connection between ALS and frontotemporal dementia (FTD)
ALS is linked to a specific type of cognitive loss called frontotemporal dementia (FTD). Both diseases cause neurodegeneration – the rapid death of brain cells. ALS destroys motor neurons, which transmit messages to and from the brain and spinal cord to the muscles. FTD involves damage to neurons in the brain’s frontal lobes (located behind the forehead) and temporal lobes (behind the ears). These areas govern executive functions like problem solving, speaking, and planning. The loss of brain cells in FTD leads to progressively worsening changes in behavior, personality, and language.
The relationship between these diseases goes two ways. Up to half of people with ALS show some damage to their frontal and temporal lobes, although only 15 percent are severe enough to qualify for a FTD diagnosis. Conversely, about 40 percent of people with FTD have movement problems, with 15 percent being severe enough to be diagnosed with ALS.
There is so much overlap between these two conditions that people who have both are said to have a combined syndrome called ALS-FTD. And in many cases, both diseases are inherited.
Researchers have discovered several gene mutations associated with ALS and FTD, particularly changes to the C9orf72 gene. More than one-third of people with ALS have this gene mutation, which is thought disrupt normal RNA and protein production, leading to the formation of damaging protein clumps in the brain that are hallmarks of both diseases.
People with ALS who also have dementia when they’re first diagnosed are more likely to have bulbar-onset ALS — a subtype that starts with symptoms in the head and neck, such as difficulty speaking or swallowing. And those who have both ALS and dementia face a poorer outcome — they don’t survive as long as those without cognitive problems, finds a 2017 study in the Journal of Neurology.
Symptoms of dementia in ALS
Dementia in people with ALS doesn’t always manifest as overtly or dramatically as it does in Alzheimer’s disease. Instead of the severe memory loss and confusion seen in Alzheimer’s, often people with ALS have more subtle cognitive symptoms that only their loved ones notice, such as:
- Inappropriate behaviors
- An inability to respond to other people’s feelings
- Repetitive actions
- Loss of motivation — apathy
- Poor hygiene
- Gradual loss of language
Treating ALS and FTD
No cure exists for either ALS or FTD. Because of the close relationship between these two conditions, it’s likely that any treatment that’s eventually developed to be effective against one disease will also work against the other.
One avenue of research focuses on the C9orf72 gene mutation. Scientists are looking at potential drugs that can block RNA damage caused by this mutation. They’re also investigating ways to halt the protein clumping that leads to nerve cell damage in both diseases.
For now, treatments for movement and cognitive loss are mainly supportive. Physical therapy can lead to some improvements in muscle weakness, while speech and language therapy can help people communicate more clearly.
March 16, 2020
Christopher Nystuen, MD, MBA