Amyotrophic Lateral Sclerosis (ALS) or ‘Charcot's Disease’ is a progressive and fatal neuromuscular pathology characterised by the progressive death of motor neurons, the neurons that control walking, speech, swallowing and breathing, among other things. This loss of motor neurons leads to muscular atrophy and progressive paralysis in patients.
Charcot's disease (ALS) is the most common motor neurone disease in adults.
There are two types of motor neuron:
- Central motor neurons, located in a specific region of our brain, the motor cortex, transmit contraction commands to the spinal cord.
Peripheral motor neurons, motor neurons located in the spinal cord, transmit motor information to the muscles. - The degeneration of these 2 types of motor neuron in ALS leads to the loss of information transmission between the brain and the voluntary muscles, which are therefore no longer solicited, do not contract and atrophy.
Motor neuron damage can sometimes be associated with a characteristic loss of neurons in the frontal and temporal regions of the brain, leading to cognitive and behavioural disorders of varying intensity. In its most severe form, this leads to fronto-temporal dementia (FTD): 15% of patients with Charcot disease also have FTD. The dementia in FTD is not characterised, as in Alzheimer's disease, by memory problems, but by behavioural changes which are at the forefront. This is reflected in changes in patients' social behaviour and personality.
The causes of Charcot's disease - is it hereditary?
For 1 in 10 patients, the origin of the disease is due to hereditary genetic mutations, known as familial cases.
The biological mechanisms of Charcot's disease
Charcot's disease or amyotrophic lateral sclerosis (ALS) is a disease affecting motor neurons, the nerve cells that control voluntary movement. These motor neurons gradually degenerate, although the precise mechanisms leading to neuronal death are not yet known. This neurodegenerative disease progresses in a few years to the point of complete paralysis.
The symptoms, progression and life expectancy of Charcot disease
The symptoms of amyotrophic lateral sclerosis (ALS), also known as Charcot's disease, are characterised by complete paralysis of the muscles of the arms, legs, mouth and tongue, as well as the respiratory muscles. This leads to an inability to use one's arms, walk, eat or speak, and to breathing difficulties that gradually set in. The disease appears in adulthood (average age 59 in France) and progresses, on average in 3 to 5 years, to complete paralysis of the muscles, eventually leading to the patient's death, generally from respiratory failure. Depending on the location of the motor neurons affected (cortical neurons, brain stem neurons and/or spinal cord neurons), the symptoms presented may vary from patient to patient, particularly at the start of the disease.
Treatment and diagnosis of Charcot disease
The diagnosis of the disease is suspected by a neurologist who, on neurological examination and questioning, finds signs and symptoms of progressive damage to the first and second motor neurons. In all cases, this is characterised by a progressive loss of muscle strength, sometimes associated with muscle wasting, or stiffness in the limbs. To make this diagnosis, the neurologist relies on the results of an examination that records the electrical signals between the neurons and the muscles: an electromyogram. This shows the motor denervation of the muscles as a result of the loss of motor neurons. In order to confirm this diagnosis, it is essential for the neurologist to be able to rule out, by means of further tests, all other possible causes of motor neuron suffering, such as mechanical compression, inflammatory attacks on the motor nerves or any other process that may damage the nerves.
In the case of familial forms (10%), the diagnosis is established with certainty when the patient carries one of the known mutations responsible for the disease. There are currently more than 30 known genes, and at least 1/3 of familial cases still have no identified genes (the proportion varies from one region of the world to another).
To date, there is no cure for Charcot's disease. However, the combination of neuroprotective treatment and multidisciplinary care that addresses all aspects of the disease can slow the progression of symptoms.
