Motor neuron disease

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at October 2, 2016
Start › Diseases › Motor neuron disease

One of the most debilitating classes of disease with a prevalence of one in 300 (according to the motor neurone disease association) is the class of conditions called motor neuron diseases. These life-changing conditions can be fatal and have a life expectancy of three to five years time. Motor neuron diseases affect the motor neurons and nerves in the central nervous system.

Contents

Definition & Facts

Motor neuron diseases include the following:

Each of these conditions is devastating to patients, and as a rule, many succumb to the disease within very few short years after being diagnosed. These conditions tend to affect neuron groups in the brain. These can include the upper motor neurons (UMN) or lower motor neurons (LMN).

In all cases, the overarching condition causes a shutdown of the motor neurons. These important parts of the central nervous system send nerve impulses from the brain to the muscle groups. In the later stages of the condition, patients will find gripping objects, walking, speaking, swallowing, and breathing increasingly difficult.

Symptoms & Complaints

Motor neuron diseases are progressive. The first symptoms may seem like a loss of coordination or acute clumsiness, but as the condition progresses through its early stages, symptoms will significantly worsen.

This clumsiness typically progresses to a weakened grip and a reduced ability to raise the arms significantly. Eventually, picking up objects will become frustratingly difficult. The majority of these early indicators happens on one side first and moves to the rest of the body over time.

The shoulders will weaken, so that it’ll be difficult to lift the arms at all and patients will eventually have issues lifting their feet when walking, causing a noticeable foot drop. This progresses to leg dragging, and the eventual inability to walk at all.

Slurred speech is also a trait that occurs and which can progress to the point at which speech is eventually nearly impossible.

Causes

The cause of the majority of motor neuron diseases is still unclear. There are some suspected causes or conditions associated with motor neuron degradation. The first suspected cause is the formation of buildups on the motor neurons themselves. These accumulating materials are almost always present on the motor neurons of patients of MND. The clumps of additional protein are thought to be the reason for the hindrance. One particular aggregate protein, TDP-43 is known to be a protein that greatly affects cellular RNA.

Another potential cause of disruption in the motor neurons is a disruption of cellular transport which reduces the neuron’s ability to transport nutrients and waste through its cellular membrane. As a result of this, waste builds up inside the neuron causing weakened functioning.

In 2014, funding was raised for research through a social media campaign called “the ice bucket challenge.” The funding raised by this promotion helped researchers pinpoint a gene called NEK1 that may be a culprit behind some motor neuron diseases like ALS.

Diagnosis & Tests

The diagnostic process will begin with the physician asking about the patient's medical history and family history. A physical examination will be administered as well as a neurological examination that tests motor and sensory responses like reflexes. In addition, a neuropsychiatric evaluation may be conducted which tests a patient for mental disorders.

A series of medical imaging tests may be administered in order to assess the function and structure of the brain and central nervous system. The first of these tests is usually a magnetic resonance imaging (MRI) scan. This test involves a patient being placed in a large, cylindrical machine that uses magnetic resonance to perform a thorough scan of bodily functions. A medical professional may perform this scan to eliminate other possible causes of symptoms.

Other imaging examinations include a computed tomography (CT) scan. An electroencephalogram (EEG) may also be performed which examines the electrical activity of the brain and can detect the location of abnormalities.

Secondly, a doctor may have a blood test administered, which will detect if the body is producing creatine kinase, a bodily compound that is generated when muscles begin to break down. Nerve conduction tests are another way that experts test for this condition. An electrical impulse in conducted through a pad on a patient’s skin and the speed in which this impulse is carried through the body is measured so that specialist can determine if nerve impulse is in some way hindered.

Similarly, the condition can be measured by means of a transcranial magnetic stimulation. This test measures the activity of the upper motor neurons.

Treatment & Therapy

The treatment plan that is used to address these conditions is usually geared towards mitigating symptoms, preserving or prolonging function, and slowing the progression of the disease. Physical therapy, occupational therapy, speech therapy, and the use of assistive devices like assistive canes, walkers, and wheelchairs all may be utilized to improve a patient's quality of life.

Strides have been made that lengthen the lives of some patients. For example, the medication riluzole has been known to add months to the lives of MND patients. In addition to this, there have been some known cases where patients with MND conditions have survived for many decades. Famed astrophysicist Stephen Hawking has had ALS for over 50 years and continues to serve as a professor.

Devices like breathing masks that help a patient compensate for reduced lung function are used. In addition to these, a feeding tube may be necessary for those in the later stages of the disease.

Prevention & Prophylaxis

Since the exact cause of motor neuron degradation is not fully understood, there is no clear way to prevent the condition at this time. Head injury can be a potential indicator for the disease, since several famous football players have gotten the condition after years in the sport. If this is the case, more stringent practices for protecting the head will be needed. 

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