What can mimic ALS?
Sophia Vance
Updated on April 02, 2026
A number of disorders may mimic ALS; examples include:
- Myasthenia gravis.
- Lambert-Eaton myasthenic syndrome.
- Lyme disease.
- Poliomyelitis and post-poliomyelitis.
- Heavy metal intoxication.
- Kennedy syndrome.
- Adult-onset Tay-Sachs disease.
- Hereditary spastic paraplegia.
Can ALS be mistaken for something else?
ALS is commonly misdiagnosed as cerebrovascular disease, cervical myelopathy, vertebral disc herniation, radiculopathy, neuropathy, and myasthenia gravis. Misdiagnosed patients may endure surgery or treatment for the wrong diagnosis that can lead to unnecessary harm.How many times is ALS misdiagnosed?
How often the first diagnosis of ALS wrong and the problem turns out to be something else? In up to about 10 to 15% of the cases, patients get what we call a false-positive. That means they are told they have ALS, but, in the end, another disease or condition is discovered to be the real problem.What can mimic ALS on EMG?
Multifocal motor neuropathy with conduction block is another mimic of ALS. It presents by onset of focal motor weakness, usually in a distal upper extremity, accompanied commonly by fasciculations and cramps.Can you have ALS and not know it?
The initial symptoms of ALS can vary from person to person. For many, the onset of the disease is so subtle that the symptoms are often overlooked. However, as symptoms begin to develop into more obvious muscle weaknesses and/or atrophy, physicians are more likely to suspect ALS in their patients.How to Give Less Bad News: A Guide to ALS Mimics - David Ivanick, MD
How do you rule out ALS?
How is ALS diagnosed?
- Electromyography (EMG) is a recording technique that detects electrical activity of muscle fibers and can help diagnose ALS.
- A nerve conduction study (NCS) measures the electrical activity of the nerves and muscles by assessing the nerve's ability to send a signal along the nerve or to the muscle.
Does ALS start abruptly?
As I have mentioned before, ALS does not start abruptly. Consider Lou Gehrig. At first he never dreamed he had a disease. That's the same problem all of our patients face.Can an EMG rule out ALS?
Nerve conduction studies and needle electromyography (EMG) are useful for confirming the diagnosis of ALS and for excluding peripheral conditions that resemble ALS. Laboratory tests are performed primarily to rule out other disease processes; results generally are normal in ALS.How accurate are EMG for ALS?
The technique appears to identify people with ALS at about 96% accuracy. And, rule out ALS, 84%. Now, a growing number of neurophysiologists are using combined methods to identify people with ALS. The strategy reduces the number of muscles that need to be checked using electrophysiological methods – including EMG.Does abnormal EMG always mean ALS?
A normal EMG result will often result in a diagnosis of primary lateral sclerosis (PLS), but does not rule out the possibility of ALS developing later.What disease has the same symptoms as ALS?
Primary Lateral Sclerosis (PLS)PLS is similar to ALS, but it affects only upper motor neurons. It causes weakness and stiffness in the arms and legs, a slowed walk, and poor coordination and balance. Speech also becomes slow and slurred. Like ALS, it usually starts in people 40 to 60 years old.