Overview of Electrodiagnostic Evaluation of Motor Neuron Disease
Motor neuron disorders are a group of diseases that affect the nerve cells in your body that control your muscles. They are quite varied, influencing different nerve cell types. Some popular motor neuron diseases include ALS (which affects both upper and lower motor neurons), primary lateral sclerosis (only impacts upper motor neurons), and diseases like progressive muscular atrophy, progressive bulbar palsy, spinal muscular atrophy, and post-polio syndrome (all of which affect lower motor neurons). You might often hear “motor neuron disease” and “ALS” used interchangeably, as ALS is the most typical version of this disease in adults.
ALS is an illness that gradually causes weakness in the muscles responsible for swallowing, breathing, and moving your arms, legs, and body. This weakness happens because specific nerve cells are dying off. Unfortunately, it is typically a fast-progressing disease, with most people passing away from breathing complications 2 to 5 years after diagnosis. Only a small portion of ALS cases is hereditary (about 10%), while the remainder appears randomly without any connection to family history. According to data, in 2014, 5 in every 100,000 people in the US had ALS.
The presentation of ALS can vary a bit from patient to patient, but the vast majority start showing symptoms of the disease through weakness in one limb (80% of patients) or difficulty speaking or swallowing (20% of patients). As the illness progresses, it spreads to other parts of the body, leading to tightened muscles, overactive reflexes, muscle wasting, and a lack of reflexes.
Many patients also experience changes in their behavior due to dysfunction in the frontal and temporal lobes of the brain; 15% of patients even develop a type of dementia called frontotemporal dementia. Some might show Pseudobulbar affect, showing involuntary and sudden bouts of laughing or crying. This condition isn’t exclusive to ALS, though, as it also occurs with other neurological diseases like strokes, Alzheimer’s disease or multiple sclerosis.
When ALS is suspected, a specific test is needed called electrodiagnostic testing. This is an important tool to examine the health of the muscle-controlling nerve cells (lower motor neurons), especially as other standard lab and imaging tests usually come back normal. Special procedures called Nerve conduction studies (NCS) and needle electromyography (EMG) help to confirm an ALS diagnosis and eliminate other diseases that may mimic ALS symptoms. By ruling out these other conditions, doctors can ensure the correct treatment course and care plan are chosen, as ALS has limited treatment options and poor prognosis.
Anatomy and Physiology of Electrodiagnostic Evaluation of Motor Neuron Disease
ALS, also known as Lou Gehrig’s disease, impacts specific nerve cells in the brain and spinal cord. These specific nerve cells, known as motor neurons, are vital. They help control our body’s voluntary muscles, which enable us to move. An important distinction is that you have two groups of these: lower motor neurons that live in the spinal cord and some parts of the brain, and upper motor neurons that exist in a part of the brain called the cerebral cortex.
Interestingly, a specific gene mutation – C9ORF72 – is responsible for around 40% of inherited (or familial) cases of ALS.
One key thing that happens in the disease is an accumulation of a protein called TDP-43. This protein normally has a major role in managing RNA, which is like a blueprint for producing our body’s proteins. It is also found in patients suffering from another nervous system disease known as frontotemporal dementia. These protein clusters are primarily found in nerve cells of parts like the hippocampus and cerebellum, which contribute to memory and coordination.
However, ALS does not seem to impact senses like touch, taste, sight, etc., as it focuses on the motor neurons. Also, a person’s ability to think or cognitive abilities are usually not affected unless concurrent frontotemporal dementia occurs, which happens in up to half of ALS cases.
Why do People Need Electrodiagnostic Evaluation of Motor Neuron Disease
Testing that measures the electrical activity of muscles and nerves, called electrodiagnostic testing, is crucial to diagnose ALS (Amyotrophic Lateral Sclerosis, a type of motor neuron disease leads to muscle weakness and impacts physical function). This is because it can identify issues with the lower motor neurons, which are cells in the brain and spinal cord that control muscle activity. You might be advised to have nerve conduction studies (NCS) and needle electromyography (EMG) if your doctor suspects you might have a motor neuron disease. These tests are an extension of the usual neurological exam.
Diagnosing someone with ALS is a serious matter because it’s a severe illness with significant implications. Therefore it’s crucial that other health conditions that look similar to ALS are ruled out. A health condition called multifocal motor neuropathy with conduction block (MMNCB) is an example of a disorder that can look a lot like ALS, and it must be effectively ruled out to ensure the correct diagnosis.
Like ALS, MMNCB usually shows up as weakness that worsens over time and is not the same on both sides of the body, and it typically doesn’t affect the sense of touch. Usually, it affects more than one motor nerve. Symptoms of MMNCB can include significant muscle weakness compared to muscle shrinkage, a lack of symptoms indicating an issue with the upper motor neurons, and more involvement of the upper arms and lack of bulbar findings, which are symptoms affecting speech and swallowing. The results of electrodiagnostic tests also appear different between these two conditions.
When a Person Should Avoid Electrodiagnostic Evaluation of Motor Neuron Disease
Doctors always need to think about the possible risks versus the benefits before doing any medical procedure. Typically, electrodiagnostic tests, which are tests that measure the electrical activity of your muscles and nerves, have very little risk. However, there are certain situations where these tests, specifically Nerve Conduction Studies (NCS) and a needle Electromyography (EMG), should not be done. These cases include severe bleeding disorders or the presence of an automatic device that helps control irregular heartbeats, known as a cardiac defibrillator.
Areas on the body where there is an active infection should not have needles inserted into them. Patients with pacemakers, a device that helps regulate the heart’s rhythm, should avoid these tests over the area where the pacemaker is located. This is because the test can be confused for an abnormal heart rhythm. It’s also important to be careful with patients who have lymphedema, a condition where excess fluid collects in tissues causing swelling, as there can be a potential risk for infection.
How is Electrodiagnostic Evaluation of Motor Neuron Disease performed
ALS, also known as Lou Gehrig’s disease, is a condition that can be hard to spot in its early stages. Often, it gets confused with other conditions. Medical professionals use a variety of techniques and tests for diagnosis, including NCS and needle EMG, which are types of nerve and muscle tests. But before they suggest these tests, doctors will usually ask about your medical history and give you a thorough physical exam. They may also recommend imaging tests such as MRI scan, and lab tests to rule out other possible conditions like brain or spinal cord tumors, multiple sclerosis, and myasthenia gravis, as they can mimic ALS.
It’s important for doctors to inform patients about these tests, especially the needle EMG which could be a bit uncomfortable. It’s equally important to keep the body warm during these tests, as having a lower body temperature could affect the results, causing inaccurate findings.
NCS, or nerve conduction study, includes tests for both sensation and motor skills. In this test, doctors attach electrodes to your skin and send small electrical shocks to the nerve that controls that area. This helps them examine any irregular nerve activity. The needle EMG, on the other hand, involves inserting a needle into your muscle to measure its electrical activity. For ALS, doctors usually test at least one upper and one lower area of your body with these studies.
When using the needle EMG, doctors look closely at areas showing signs of lower motor neuron damage, like muscle wasting and weakness, and absent reflexes. They normally examine muscles in a minimum of three limbs, choosing muscles that are controlled by at least two different nerves. They also test at least one muscle in the throat or neck region and two in the areas either side of your spine in your chest region.
Possible Complications of Electrodiagnostic Evaluation of Motor Neuron Disease
Like any medical procedure, introducing something foreign into the body comes with some risk. One of these procedures is called needle EMG, a test that checks the health of your muscles and nerve cells. Thankfully, the risk of getting an infection from this procedure is very low, less than 1 in 10,000. However, there is also a small chance of bleeding. Because of this, it’s typically recommended that patients with serious bleeding disorders avoid this procedure.
What Else Should I Know About Electrodiagnostic Evaluation of Motor Neuron Disease?
Amyotrophic lateral sclerosis (ALS) is a disease that affects nerves in your brain and spinal cord that control muscle movement. This disease is typically diagnosed through a clinical examination and with the help of a special test called an electrodiagnostic evaluation. This test is important as it can identify issues with the ‘motor neurons’ – the nerve cells that control our muscle movement.
The typical signs of ALS include physical symptoms related to motor dysfunction such as weakness in the limbs or difficulty swallowing. This is combined with evidence of upper and lower motor neuron damage. Lower motor neurons are those that send signals from the brain and spinal cord to the muscle, whereas upper motor neurons send signals from the brain to the spinal cord.
In diagnosing ALS, doctors use a standard set of guidelines called the El Escorial criteria. According to these criteria, there should be evidence of both upper and lower motor neuron signs, and the disease should progressively spread from one body area to another. The test also helps to rule out other possible causes for the symptoms. In 2006, the criteria were updated to increase the sensitivity of the evaluation.
Other studies to confirm ALS include motor nerve conduction studies which examine specific muscles and their corresponding nerves to look for abnormalities. Also, sensory nerve conduction studies should be normal in ALS patients as ALS does not typically affect the sensory nerves. If sensory nerves are affected, it usually points to another disease.
An assessment of acute (short-term) denervation and chronic (long-term) reinnervation of nerves using a needle EMG (electromyography) is also performed, which provides evidence of nerve damage. Additionally, they will also perform F-wave studies, which indirectly stimulate motor neurons to understand more about your disease progression.
ALS is a complex disease, and these evaluations represent a collection of tests that doctors use to make an accurate diagnosis. If you are diagnosed with ALS or a similar condition, understanding these tests can be important to talk to your doctor about your disease and its progression.