Two motor nerve cells are connected in series for muscle excitation. The first motor neuron originates in the brain and is switched to the second motor neuron in the spinal cord at the level where it connects to a peripheral nerve to reach the corresponding muscle. If the second motor neuron (peripheral nerve) is damaged, flaccid paralysis occurs, while damage to the first motor neuron (brain/spinal cord) results in spastic paralysis.
Since both motor neurons are affected, amyotrophic lateral sclerosis is characterised by the joint occurrence of both flaccid and spastic paralysis, which begins so slowly and insidiously that the patient’s impairments are initially dismissed by the latter as “clumsiness”. From gait or gripping problems of the hand due to slackness or stiffness of the muscles, to holding difficulties of the trunk and later also difficult breathing, various limitations can be expected. In most cases, the symptoms of failure begin in the extremities and it is only in the later course of the disease that the trunk and bulbar muscles (swallowing and speaking muscles) are also involved.
However, in about one in three patients the disease begins as a bulbar form with impairment of swallowing and speaking, which leads to clotted speech and increased swallowing. The speech disorder may require communication aids such as alphabet boards, writing boards or the like to enable the patient to make himself understood. Furthermore, a regression of the flaccid paralysed muscles is a typical symptom, which can be easily observed on the hand due to its loss of shape, but also occurs elsewhere on the body.
The musculature of the eyes is never affected. The early symptoms of amyotrophic lateral sclerosis are characterized by the fact that they can take very different forms, just like the actual course of the disease. Often, however, the first symptoms are very unspecific and are often not noticed by those affected.
This often leads to stumbling or problems in holding things, which are usually dismissed by patients as clumsy. With time, however, these circumstances usually increase and slowly the first painless paralysis symptoms on the arms or legs are noticed. From this type of rule one must distinguish the so-called bulbar beginning.
This initially affects nerve cells of the brain stem, which are responsible for swallowing or speech production. The first symptoms are a beginning swallowing disorder or speech disorders. However, this form of the disease is very rare.
One of the most important features of amyotrophic lateral sclerosis is that the increasing paralysis occurs without pain or sensation. It is therefore rather untypical for affected persons to report a pronounced tingling sensation or other forms of paralysis such as itching. The occurrence of speech disorders is very typical for the bulbar course of amyotrophic lateral sclerosis (ALS).
It is peculiar to this disease that it starts in the region of the brain stem. Therefore, the degeneration of the motor nerve cells can lead to speech disorders, but also to swallowing disorders. Therefore, the symptoms mentioned here are at the beginning of the course of the symptoms.
The more frequent course must be distinguished from this, where the first symptoms affect the legs and/or the arms. In this type of course, the continuously increasing course of the disease, after a pre-existing symptomatology in the extremities, leads to an extension of the disease to the brain stem and thus to swallowing and speech disorders. ALS is peculiar in that the increasing paralysis is described by most patients as painless, since the isolated death of the motor nerve cells of the spinal cord does not trigger a pain stimulus.
Despite this fact, some patients report severe pain that increases as the disease progresses. The exact cause of this has not yet been finally clarified. Some patients can develop severe headaches due to the lack of oxygen caused by paralysis of the respiratory muscles.