ALS is part of a group of disorders called motor neuron diseases, which also includes other conditions with similar symptoms. Additionally, there are other disorders that exhibit symptoms similar to those of ALS but are not classified as motor neuron diseases.
Areflexia: Absence of reflexes.
Hyperreflexia: Excessively increased reflexes.
Lower motor neurons (LMN): Nerves that directly stimulate muscles.
Upper motor neurons (UMN): Nerves that control and modulate lower motor neurons.
Signs: Observable indicators of a disease detected by a healthcare professional.
| Table: Motor Neuron Diseases | ||||
|---|---|---|---|---|
| Name | Abbreviation | UMN signs | LMN signs | Notes |
| Amyotrophic Lateral Sclerosis | ALS, MND | ✓ | ✓ | -- |
| Monomelic Amyotrophy (Hirayama Disease) | MMA | Caused by nerve compression in cervical spine; most common in Asia | ||
| Primary Lateral Sclerosis | PLS | ✓ | Far slower progression than ALS | |
| Progressive Bulbar Palsy | PBP | ✓ | ✓ | Variant of ALS, affects bulbar region only |
| Progressive Muscular Atrophy | PMA | ✓ | Somewhat slower progression than ALS | |
| Spinal and Bulbar Muscular Atrophy (Kennedy's Disease) | SBMA | ✓ | Rarely affects females | |
| Spinal Muscular Atrophy | SMA | ✓ | ✓ | Typically diagnosed in infants and young children |
| Table: Motor Neuron Disease Symptoms | ||||||
|---|---|---|---|---|---|---|
| Disease Name | Abbreviation | Spasticity | Areflexia | Hyperreflexia | Fasciculations | Muscle weakness and atrophy |
| Amyotrophic Lateral Sclerosis | ALS, MND | ✓ | ✓ | ✓ | ✓ | |
| Monomelic Amyotrophy (Hirayama Disease) | MMA | ✓* | ✓ | ✓ | ||
| Primary Lateral Sclerosis | PLS | ✓ | ✓ | ✓ | ✓ | |
| Progressive Bulbar Palsy | PBP | ✓ | ✓ | ✓ | ✓ | |
| Progressive Muscular Atrophy | PMA | ✓ | ✓ | ✓ | ||
| Spinal and Bulbar Muscular Atrophy (Kennedy's Disease) | SBMA | ✓ | ✓ | |||
| Spinal Muscular Atrophy | SMA | ✓ | ✓ | ✓ | ||
|
*: rarely encountered |
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Primary Lateral Sclerosis (PLS) differs from ALS in that lower motor neurons are not affected, unlike in ALS. Some neurologists consider PLS to be a precursor to ALS; i.e. they consider PLS to be an incomplete initial progression of ALS.
PLS is known to progress significantly lower than ALS.
Most charities and societies that support individuals with ALS and facilitating ALS research often also offer support to individuals with PLS.
Progressive Bulbar Palsy (PBP) is a variant of ALS that only affects the bulbar region. The limbs and respiratory system remain unaffected in PBP.
| Table: disorders whose symptoms and signs mimic motor neuron diseases5 | |
|---|---|
| Name | Description |
| Adrenoleukodystrophy | Genetic condition that causes demyelination |
| Central nervous system tumors | Abnormal cell formation in the brain and/or spinal cord which affects the central nervous system |
| Cervical and lumbar myelopathy | Spinal cord injuries that affect the nerves |
| Chronic inflammatory demyelinating polyradiculoneuropathy | Autoimmune disorder where the myelin sheath of nerves is attacked |
| Human Immunodeficiency Virus (HIV) | Virus, causing failure of the immune system; infections become able to thrive, causing harm |
| Inflammatory myopathies | A group of diseases that can cause pain, weakness, and inflammation of muscles |
| Lambert-Eaton Syndrome | Autoimmune disorder where the connection between nerves and muscles is attacked |
| Lyme disease | Bacterial infection that can harm the nervous system |
| Multifocal motor neuropathy with conduction block | Autoimmune disorder where the myelin sheath of nerves is attacked |
| Multiple Sclerosis | Autoimmune disorder where the myelin protecting nerves in the brain and spinal cord is attacked |
| Myasthenia gravis | Autoimmune disorder where the signals from the brain to the muscles are disrupted |
| Polyradiculopathy | A group of peripheral nervous system disorders where motor, sensory, and reflexes can be affected |
| Syringomyelia | Neurological disorder where a cyst forms in the spinal cord |