“We no longer use the term dementia, which has a negative connotation. We are talking about cognitive disorders mild, moderate or major”, recalls in the preamble Dr Camille Heitz, neurologist. “Dementia” is characterized by a progressive decline in cognitive functions (memory, language, orientation, gestures,) for at least 6 months. “More precisely, the term ‘dementia’ is equivalent to the term ‘major cognitive disorders’ and necessarily implies a Autonomy loss. People are no longer able to manage their daily lives alone. It starts with financial and administrative management, up to the loss of autonomy for shopping, cooking, washing, etc.”, explains the neurologist.
What are the different causes of “dementia”?
It is first necessary to have ruled out a medicinal or psychiatric origin or even a head trauma. We can then classify “dementias” according to two main causes: neurodegenerative causes and vascular causes.
Degenerative “dementias”
Among the degenerative “dementias”, we find there Alzheimer’s disease which is by far the most common (around 80% of causes of dementia). “It is mainly manifested by memory problems recent memories”, recalls the neurologist. But there are also other neurodegenerative “dementias”: the DFT (Frontotemporal degeneration) which affects younger people and mainly leads to behavioral problems, there Lewy body disease which is similar to Parkinson’s disease and can also cause visual hallucinations.
Vascular causes
“‘Vascular dementias’ are linked to blood circulation problems in the brain. There may be vessels that become blocked or bleed, these are generally microscopic vessels and these phenomena go unnoticed but over time the lesions accumulate and can cause dementia.”, explains Dr. Heitz. The main cause is high blood pressure.
In addition to these two main causes, there are many others, particularly following alcoholism or certain infectious diseases (HIV, syphilis For example).
Dementia: how to distinguish the different forms of major neurocognitive disorders?
“Until now, we had few tools to know the cause of dementia during the patient’s lifetime. All descriptions of these diseases were therefore based on symptoms and the diagnostic criteria remained purely clinical for a long time (questioning and examination by the doctor).”, explains Dr. Heitz. The latter, however, specifies that thanks to the evolution of medicine, it is now possible to be more precise in diagnoses. This made it possible to realize that different diseases shared the same symptoms. “For example, the first drug trials in Alzheimer’s disease were carried out using clinical criteria. We realized a few years later that nearly 25% of the patients included did not actually have Alzheimer’s disease! This probably contributed to the failure of this type of test.”, explains the neurologist.
Distinguish these diseases based on the protein involved
Rather than relying on a purely clinical diagnosis, it would therefore be fairer to distinguish these diseases according to their cause, that is to say the protein involved. “We distinguish 3 main types of diseases according to this classification: amyloidopathies linked to amyloid protein (of which Alzheimer’s disease is a part), taupathies linked to the Tau protein (of which the DFT is a part) and synucleinopathies linked to the alpha-synuclein protein (of which Parkinson’s disease is a part)”, explains Dr. Heitz. “This classification has the merit of knowing which protein we are trying to treat to cure patients. Current research therefore seeks to identify these proteins in patients with blood tests or lumbar puncture”, she adds.
Thanks to Dr Camille Heitz, neurologist (ICT, Trocadéro Brain Institute, Paris)