ALS vs Polio and spinal muscular atrophy
How to tell ALS and Polio and spinal muscular atrophy apart when a board question makes them look alike.
ALS is adult mixed UMN/LMN motor degeneration; polio is infectious LMN paralysis; SMA is infant genetic anterior horn disease.
Side by side
ALS causes progressive combined upper and lower motor neuron signs, fasciculations, weakness, hyperreflexia, spasticity, and usually preserved sensation and cognition early.
Polio causes asymmetric lower motor neuron paralysis after poliovirus infection; Werdnig-Hoffmann spinal muscular atrophy causes infantile hypotonia, tongue fasciculations, and anterior horn cell degeneration from SMN1 mutation.
Degeneration of corticospinal upper motor neurons and anterior horn lower motor neurons produces mixed motor signs.
Poliovirus destroys anterior horn cells; SMA causes genetic anterior horn cell loss from impaired SMN protein.
Mixed UMN/LMN signs in multiple regions with normal sensory exam support ALS.
Post-infectious asymmetric flaccid paralysis supports polio; infantile hypotonia with SMN1 deletion supports SMA.
The trap
Fasciculations and weakness overlap, so UMN signs, age, infection, and genetics separate them.
The repair move
For motor neuron disease, ask whether upper motor neuron signs are present and whether the setting is adult, infectious, or infantile genetic.
Try a free question
CoreAn adult has progressive hand weakness, fasciculations, muscle atrophy, hyperreflexia, spasticity, and preserved sensation. Which diagnosis is most likely?
Show answer and explanation
Answer: A. ALS. Progressive mixed UMN and LMN signs with preserved sensation support ALS.
Why the other choices are tempting
- B. Polio causes infectious lower motor neuron paralysis without UMN signs.
- C. SMA type 1 presents in infancy with hypotonia and tongue fasciculations.
- D. GBS causes acute ascending weakness with sensory/autonomic features and areflexia.
- E. MS causes CNS demyelinating episodes with sensory and other CNS signs.
Flashcards
Tap a card to flip it.
What motor sign combination points to ALS?
Combined upper and lower motor neuron signs point to ALS.
What sensory pattern supports ALS?
Preserved sensation supports ALS as a motor neuron disease.
Quick answers
What is the fastest way to tell ALS from Polio and spinal muscular atrophy?
ALS is adult mixed UMN/LMN motor degeneration; polio is infectious LMN paralysis; SMA is infant genetic anterior horn disease.
What is the key clue for ALS?
ALS causes progressive combined upper and lower motor neuron signs, fasciculations, weakness, hyperreflexia, spasticity, and usually preserved sensation and cognition early.
What is the key clue for Polio and spinal muscular atrophy?
Polio causes asymmetric lower motor neuron paralysis after poliovirus infection; Werdnig-Hoffmann spinal muscular atrophy causes infantile hypotonia, tongue fasciculations, and anterior horn cell degeneration from SMN1 mutation.
What is the common trap with ALS vs Polio and spinal muscular atrophy?
Fasciculations and weakness overlap, so UMN signs, age, infection, and genetics separate them.