Few people had probably heard of frontotemporal dementia until earlier this year, when the family of actor Bruce Willis announced that the 68-year-old had been diagnosed with the condition.
Frontotemporal dementia is a rare condition – it is estimated to account for only one in 20 cases of dementia. Symptoms usually appear in the late 50s and first affect behavior, personality and language ability. Unlike other forms of dementia, memory is only impaired in the later stages of the disease.
People with frontotemporal dementia usually die within eight years of their diagnosis. While approximately 30% of cases are hereditary, the cause of frontotemporal dementia is largely unknown. This also means that there is no cure or treatment to slow its progression.
But recent research, which I published with colleagues at Lund University, may have taken us a step further in our understanding of how frontotemporal dementia develops and progresses. We found that the way your brain looks can determine your resilience to this disease.
During pregnancy, as the fetal brain develops in the uterus, it develops its distinctive folds while extending into the skull. These brain folds play an important role in our later cognitive function.
The folds that form during early fetal development are found on both sides of the brain in every person. But there is a kink that sometimes develops later in the process. This is called the paracingulate sulcus – and not everyone has it. In those who have it, it may be present either on one side of the brain or on both sides.
The paracingulate sulcus is interesting because its presence can make a significant difference in cognitive abilities. For example, research has shown that people with a left but not right paracingulate sulcus have a cognitive advantage: they perform better on tasks involving control and even memory.
Given the link between the paracingulate sulcus and cognitive function, our research team at Lund University – alongside colleagues in the US and Amsterdam – began investigating the role of this brain fold in dementia.
To truly understand the role the paracingulate sulcus plays, the team decided to focus on a type of dementia in which brain damage occurs in the same region as this brain fold. The obvious choice for this research was frontotemporal dementia. This aggressive form of early dementia primarily attacks the frontal lobes of the brain, particularly the central parts surrounding the paracingulate sulcus.
Our team studied MRI images of the brains of 186 people diagnosed with frontotemporal dementia. We excluded participants with genetically induced frontotemporal dementia. About 57% of participants had a paracingulate sulcus on the right side of their brain.
We found that in participants who had this extra fold on the right side of their brain, their dementia symptoms began on average two and a half years later. This could mean that the paracingulate sulcus may delay the onset of symptoms. These results were statistically significant – demonstrating that they were not due to chance or other factors.
This two and a half year delay in symptom onset may not seem like much, but given the disease’s poor prognosis and symptom burden, it is an extremely significant amount of time for patients and their loved ones. .
That said, once symptoms appeared, patients with this extra brain fold became sicker more quickly and survived shorter than patients without it. So, despite the delay in symptoms, patients with and without this extra brain fold died at the same age.
Although it may seem strange that one factor can both delay symptoms and then accelerate them, this paradox is a key feature of a principle called “brain reserve” in neuroscience. Brain reserve describes a structure in the brain that provides resilience to disease before symptoms develop.
There comes a critical moment when the disease overcomes these protective mechanisms and the patient develops symptoms. After this critical point, people with high brain reserve decline rapidly – more quickly than people with low brain reserve.
For example, high brain reserve explains why Alzheimer’s disease appears later in highly educated people – even though the disease progresses more quickly in them when symptoms appear. According to our research, the paracingulate groove works on a similar principle: it first protects people from symptoms, then progresses quickly when symptoms appear.
Our research is the first to identify a protective structure in the brain that delays the onset of symptoms in people with frontotemporal dementia. If we can now discover a way to preserve this protective quality, it could lead to the development of treatments to keep symptoms – and disease – at bay.
This article is republished from The Conversation under a Creative Commons license. Read the original article.