Differences Between Myasthenia Gravis And ALS
Amyotrophic Lateral Sclerosis (ALS) and Myasthenia Gravis (MG) are two distinct neurological disorders. Although both lead to muscle weakness, their causes, progression, and symptoms are different. While ALS is considered a neurodegenerative disease, MG is referred to as autoimmune. Myasthenia Gravis affects the communication between nerves and muscles, leading to muscle weakness, while ALS is a progressive disease that destroys nerve cells, causing disability.
What Is Myasthenia Gravis?
Myasthenia gravis (MG) is a neuromuscular disorder [1].
It is characterized by disruptions of the neuromuscular junctions in the peripheral nervous system [1, 2]. These disruptions are caused by the body’s antibodies which are directly targeting proteins on the neuromuscular junction like AchR, MuSK, or others. This in turn then leads to disruption of the communication between nerves and muscles [1, 2].
Clinically, the core symptom of MG is muscle weakness or excessive fatigue of skeletal muscles [1, 2]. However, other clinical manifestations of the disease have been observed and can vary in severity and location among patients. These include problems with walking, breathing, droopy eyelids, or double vision [1, 2].
Interestingly around 80% of all the patients with MG have reported droopy eyes and double vision as one of their first symptoms. Only after this, they reported the clinical symptoms extending into other muscles [3].
What Is Amyotrophic Lateral Sclerosis?
Amyotrophic Lateral Sclerosis (ALS) is a neurodegenerative disease affecting motor neurons.
It is progressively worsening and is characterized by the loss of motor neurons in the spinal cord, brain stem, and motor cortex [4, 5, 6]. The loss of neurons is caused by a buildup of proteins such as TDP-43, FUS, or SOD1 protein which form inclusions in the aforementioned brain areas.
ALS symptoms show muscle weakness and disability. Affected individuals lose the ability to walk independently, and they often have problems swallowing and breathing, which leads to a complete dependency. Learn more about the 7 stages of ALS.
What Is The Difference In The Prevalence Of ALS vs MG?
The prevalence of ALS is 2-4 per 100,000 and interestingly ALS is more common in men than in women [6, 7]. The risk of developing ALS is therefore higher for men than women and also higher for those who have served in the military [6].
Genetics of MG and ALS
Similarly to MG, most cases of ALS are sporadic and occur without a clear familial link. However, around 5-10% of all ALS cases are familial and have been inherited [8].
What Is The Diagnosis Of ALS vs MG?
Amyotrophic lateral sclerosis (ALS) and Myasthenia Gravis (MG) are two distinct neurological disorders, each with its own unique diagnostic criteria. However, their coexistence in a patient can present a diagnostic challenge due to overlapping symptoms.
Although there is a slight overlap of the clinical symptoms of ALS and MG, both have their own unique diagnostic criteria.
ALS is usually diagnosed based on both clinical and neurophysiological findings. This includes upper motor neuron signs in the lumbar region,
For instance, electromyoneurography is used as a technique to determine active and chronic denervation of the cervical and lumbosacral regions [9].
On the contrary, MG is usually diagnosed based on the presence of specific antibodies (e.g., anti-AchR antibody). This can be either done from blood testing by isolating and analyzing the serum, or an edrophonium test [1].
Further, electrodiagnostic testing may be performed in order to measure the delays in nerve conduction to the neuromuscular junction [1].
In some cases, MG can mimic ALS, or these two conditions can also coexist [2]. This is usually when it involves the bulbar muscles and causes muscle atrophy. However, there are diagnostic criteria that can distinguish these two such as the speed of progression of the disease, clinical improvement, development of double vision, or the absence of signs of upper motor neuron involvement [2].
In rare cases, patients may be diagnosed with both ALS and MG. In these cases, the onset of the two conditions can vary, with some patients developing MG first and others developing ALS first. The co-occurrence of these two diseases is rare and requires careful interpretation of clinical symptoms [6, 7].
Treatment Options For ALS And MG
There is no cure for ALS and as the disease progresses death occurs usually death due to respiratory failure. This happens usually 2-5 years after the disease onset [9] that occurs typically 2-5 years after the disease onset [9].
However, what can be offered to the patient are symptoms-modifying treatments in the forms of physical rehabilitation, speech therapy, or medical drugs like Tofersen, Riluzole, or Edaravone [10].
Similarly to ALS, the current treatment for Myasthenia gravis is focused on managing the symptoms and improving the quality of life of the patients.
The first line of treatment for MG includes acetylcholinesterase inhibitors (e.g., pyridostigmine), which improve communication between nerves and muscles [11, 12, 13, 14]. Overall acetylcholinesterase inhibitors can help to alleviate muscle weakness.
Further, immunosuppressive drugs like corticosteroids and azathioprine are also used to reduce the production of antibodies that are causing the symptoms of MG [11, 12, 13, 14].
In some patients, a surgical procedure called thymectomy can help to improve symptoms in some patients. It consists of the removal of the thymus gland, which often is enlarged in patients affected by MG [11, 12, 13, 15].
Patients with severe symptoms can get recommended therapies like intravenous immunoglobulin or plasmapheresis. These can help to remove the harmful antibodies from the bloodstream [3, 12, 13].
Recently, new treatments that can target specific components of the immune system like B, T cells, cytokines, and the complement cascade have been developed and can potentially serve as a new line of treatment for MG [4, 15].
While these treatments can help with symptom management, they do not cure MG. The choice of treatment should be individualized considering other diseases, disease severity, and antibody status [11].
Conclusion
ALS and MG are two different conditions both involving the nervous system. However, although some of the symptoms overlap, the cause, treatment and clinical manifestation differ [16].
MG is caused by impaired communication between nerves and muscles which is a result of increased activity of autoantibodies on proteins involved in the neuromuscular junction. It mainly involves the junctions in the peripheral nervous system and is also considered an autoimmune disease.
On the other hand, ALS is a neurodegenerative disease acting on the central nervous system. It is caused by the buildup of protein inclusions.
Both diseases present with muscle weakness, however, the symptoms in ALS often start in the limbs (this is not true for Bulbar onset ALS) while in MG the initial symptoms can be ocular, generalized, or bulbar [1, 17].
These two conditions differ in the speed of their progression as well. ALS is usually more rapid and aggressive compared to MG [1, 18, 19].