What is ALS (Amyotrophic Lateral Sclerosis)?
ALS is a fatal, progressive neurodegenerative disease that destroys both upper motor neurons in the brain and lower motor neurons in the brainstem and spinal cord, causing relentless muscle weakness that spreads throughout the body and typically results in death from respiratory failure within 2-5 years of symptom onset. 1
Disease Characteristics
ALS affects approximately 25,000 individuals in the United States and manifests as progressive, painless muscle weakness that begins focally and spreads systematically 1:
- 65% present with limb weakness (hand weakness or foot drop)
- 20-25% present with bulbar symptoms (speech or swallowing problems)
- 5-10% present with axial weakness (bent posture)
The hallmark clinical feature is the combination of upper motor neuron signs (muscle stiffness, spasticity) and lower motor neuron signs (weakness, fasciculations, atrophy, flaccidity) occurring simultaneously 1, 2.
Genetics and Etiology
Approximately 90% of ALS cases are sporadic without known genetic mutations, while 10% are familial 3. Among familial cases:
- 40% have pathogenic variants in C9orf72 gene
- 20% have pathogenic variants in SOD1 gene
- Over 60 genes total have been associated with ALS, most inherited in autosomal dominant patterns 1
The disease mechanism remains incompletely understood, though environmental risk factors and gene-environment interactions likely play complex roles 3.
Clinical Course and Prognosis
There is currently no cure for ALS 3. The disease follows a relentless progressive course with:
- Mean survival of 3-5 years from diagnosis 1
- Death typically from respiratory muscle weakness 1
- Progressive spread of weakness through the musculature
- Sensory, autonomic, and oculomotor neurons remain spared 4
Diagnosis
ALS is diagnosed by exclusion, requiring 2:
- History of slowly progressive motor symptoms
- Both UMN and LMN signs on neurological examination
- Clear spread of symptoms through the body
- Exclusion of other disorders causing similar symptoms
- EMG compatible with LMN loss
Electromyography and nerve conduction studies are key diagnostic tools 5.
Disease Spectrum
ALS forms a clinical continuum with frontotemporal dementia (FTD), with overlapping genetics and pathology 2. Cytoplasmic mislocalization of TDP-43 protein serves as the pathological hallmark for both conditions.
Critical Care Implications
The rapidly progressive nature of ALS with average life expectancy of 2-5 years from onset creates unique challenges 3:
- Traditional reimbursement models based on slower timelines and potential for functional improvement are misaligned with ALS needs
- Delays in equipment approval and delivery can result in catastrophic safety risks rather than simple inconvenience
- Multidisciplinary clinic care is standard and associated with decreased healthcare utilization, prolonged survival (4-7 months), and higher quality of life 1, 3