Spinal Amyotrophic Lateral Sclerosis
Overview
Spinal amyotrophic lateral sclerosis (spinal ALS), also known as classic ALS or Charcot's disease, is the most common form of ALS, representing approximately 65-70% of all cases. This variant initially affects the limbs, particularly the upper extremities, with involvement of both upper motor [neurons](/entities/neurons) (corticospinal tract) and lower motor neurons (anterior horn cells). [^1]
Epidemiology
- Prevalence: 4-6 per 100,000 population
- Incidence: 1-2 per 100,000 annually
- Age of onset: Typically 55-60 years (younger than bulbar onset)
- Gender distribution: Male predominance (1.5-2:1)
- Geographic variation: Higher incidence in some populations (e.g., Guam, Kii Peninsula)
Genetics
Familial ALS (~5-10% of cases)
| Gene | Inheritance | Frequency | Phenotype | [^2]
|------|-------------|-----------|-----------| [^3]
| [C9orf72](/entities/c9orf72) | Autosomal dominant | ~40% of familial | Earlier onset, bulbar involvement | [^4]
| SOD1 | Autosomal dominant | ~15-20% | Aggressive, limb onset | [^5]
| TARDBP | Autosomal dominant | ~5% | Variable | [^6]
| FUS | Autosomal dominant | ~5% | Younger onset | [^7]
| ANG | Autosomal dominant | Rare | Variable | [^8]
Sporadic ALS (~90-95% of cases)
- No clear family history
- Similar genetic susceptibility factors
- Environmental factors may play a role
- De novo mutations possible
Pathophysiology
Core Pathological Mechanisms
...Spinal Amyotrophic Lateral Sclerosis
Overview
Spinal amyotrophic lateral sclerosis (spinal ALS), also known as classic ALS or Charcot's disease, is the most common form of ALS, representing approximately 65-70% of all cases. This variant initially affects the limbs, particularly the upper extremities, with involvement of both upper motor [neurons](/entities/neurons) (corticospinal tract) and lower motor neurons (anterior horn cells). [^1]
Epidemiology
- Prevalence: 4-6 per 100,000 population
- Incidence: 1-2 per 100,000 annually
- Age of onset: Typically 55-60 years (younger than bulbar onset)
- Gender distribution: Male predominance (1.5-2:1)
- Geographic variation: Higher incidence in some populations (e.g., Guam, Kii Peninsula)
Genetics
Familial ALS (~5-10% of cases)
| Gene | Inheritance | Frequency | Phenotype | [^2]
|------|-------------|-----------|-----------| [^3]
| [C9orf72](/entities/c9orf72) | Autosomal dominant | ~40% of familial | Earlier onset, bulbar involvement | [^4]
| SOD1 | Autosomal dominant | ~15-20% | Aggressive, limb onset | [^5]
| TARDBP | Autosomal dominant | ~5% | Variable | [^6]
| FUS | Autosomal dominant | ~5% | Younger onset | [^7]
| ANG | Autosomal dominant | Rare | Variable | [^8]
Sporadic ALS (~90-95% of cases)
- No clear family history
- Similar genetic susceptibility factors
- Environmental factors may play a role
- De novo mutations possible
Pathophysiology
Core Pathological Mechanisms
Mermaid diagram (expand to render)
Molecular Pathology
[TDP-43](/mechanisms/tdp-43-proteinopathy) proteinopathy
- TDP-43 inclusions in ~95% of ALS cases
- Cytoplasmic mislocalization
- Loss of nuclear function
- RNA splicing disruption
RNA metabolism
- Abnormal RNA splicing
- Impaired RNA transport
- Stress granule formation
- Translation dysregulation
Excitotoxicity
- Glutamate excess
- AMPA/Kainate receptor overactivation
- Calcium influx
- Mitochondrial damage
Mitochondrial dysfunction
- Energy failure
- [ROS](/entities/reactive-oxygen-species) production
- [Apoptosis](/entities/apoptosis) initiation
- Axonal transport defects
Neuroinflammation
- Microglial activation
- Astrogliosis
- Cytokine release
- Autoimmune components
Neuropathology
- Motor [cortex](/brain-regions/cortex): Betz cell loss, corticospinal tract degeneration
- Spinal cord: Anterior horn cell loss, gliosis
- Cranial nerve nuclei: XII (hypoglossal) involvement in some cases
- Extrapyramidal structures: Substantia nigra involvement
- Frontal cortex: TDP-43 pathology in some cases
Clinical Presentation
Initial Symptoms (Limb Onset)
Upper Limb Onset (40-50%)
- Weakness: Often asymmetric, starting in intrinsic hand muscles
- Atrophy: Thenar/hypothenar wasting
- Fasciculations: Early muscle twitches
- Clumsiness: Dropping objects, difficulty with fine motor tasks
- Cramps: Painful muscle contractions
Lower Limb Onset (20-30%)
- Foot drop: Difficulty with heel walking
- Gait disturbance: Stumbling, tripping
- Leg weakness: Proximal or distal
- Cramps: Especially at night
Disease Progression
| Phase | Timeline | Characteristics |
|-------|----------|-----------------|
| Prodromal | Months 0-6 | Subtle weakness, clumsiness |
| Early | Months 6-18 | Focal deficits, spreading to adjacent regions |
| Middle | Months 18-36 | Generalized weakness, respiratory involvement |
| Late | Months 36-60 | Severe quadriparesis, complete dependence |
| End-stage | >60 months | Locked-in state, respiratory failure |
Neurological Examination
Upper Motor Neuron Signs
- Hyperreflexia
- Pathological reflexes (Babinski, Hoffmann)
- Spasticity
- Pseudobulbar affect
Lower Motor Neuron Signs
- Muscle weakness
- Atrophy
- Fasciculations
- Hyporeflexia/areflexia
Respiratory Involvement
- Diaphragmatic weakness: Usually occurs 1-3 years after onset
- Nocturnal hypoventilation: Early sign
- Forced vital capacity (FVC) decline: ~2-4% per month
- Sniff nasal pressure: Sensitive measure of respiratory muscle strength
Associated Features
| Feature | Frequency |
|---------|-----------|
| Pain | 40-60% |
| Cognitive change | 15-20% |
| Frontotemporal dementia | 5-10% |
| Sensory symptoms (non-specific) | 10-20% |
Diagnosis
Revised El Escorial Criteria (1998)
Definite ALS:
- Clinical evidence of UMN signs in 3 regions
- OR clinical evidence of UMN in 1+ regions AND LMN in 3+ regions
Probable ALS:
- Clinical evidence of UMN and LMN signs in 2 regions
- UMN signs above LMN signs
Possible ALS:
- Clinical evidence of UMN signs in 1+ regions
- OR LMN signs in 2+ regions
Suspected ALS:
Awaji Criteria (2006)
- Combined clinical and EMG criteria
- Earlier diagnosis possible
- Fasciculation potentials = evidence of denervation
Gold-Standard Tests
| Test | Purpose |
|------|---------|
| EMG | Confirm diffuse denervation |
| Nerve conduction | Exclude neuropathy |
| MRI brain/cervical | Exclude structural disease |
| Genetic testing | C9orf72, SOD1, TARDBP, FUS |
| Pulmonary function | Baseline and monitoring |
Biomarkers (Emerging)
- [Neurofilament light](/biomarkers/neurofilament-light-chain-nfl) chain (NfL): Prognostic marker
- Phosphorylated neurofilament heavy chain (pNfH): Disease progression
- CSF/total [tau](/proteins/tau): Disease staging
- Genetic panels: Diagnostic confirmation
Differential Diagnosis
- [Cervical spondylotic myelopathy](/diseases/cervical-spondylotic-myelopathy)
- [Multifocal motor neuropathy](/diseases/multifocal-motor-neuropathy)
- [Kennedy disease](/diseases/kennedy-disease)
- [Myasthenia gravis](/diseases/myasthenia-gravis)
- [Spinal muscular atrophy](/diseases/spinal-muscular-atrophy)
- [Hereditary spastic paraplegia](/diseases/hereditary-spastic-paraplegia)
- [Toxic neuropathy](/diseases/toxic-neuropathy)
Management
Disease-Modifying Therapies
Approved Treatments
Riluzole (1995)
- Reduces glutamate excitotoxicity
- Extends survival by 2-3 months
- Side effects: Nausea, liver dysfunction
Edaravone (2017)
- Antioxidant
- Slows functional decline
- IV infusion cycles
- Selected patients
Symptomatic Management
| Symptom | Treatment |
|---------|-----------|
| Muscle cramps | Quinine, mexiletine, baclofen |
| Spasticity | Baclofen, tizanidine, benzodiazepines |
| Sialorrhea | Glycopyrrolate, botulinum toxin |
| Pseudobulbar affect | Dextromethorphan/quinidine |
| Pain | Analgesics, gabapentinoids |
| Depression/anxiety | SSRIs, counseling |
Multidisciplinary Care
Core Team
- Neurologist (ALS specialist)
- Pulmonologist
- Dietitian
- Physical therapist
- Occupational therapist
- Speech-language pathologist
- Social worker
- Mental health professional
Key Interventions
Respiratory care
- Baseline FVC monitoring (monthly)
- Non-invasive ventilation (BiPAP) when FVC <50%
- Cough assist device
- Secretion management
Nutritional support
- Weight monitoring
- Caloric intake optimization
- PEG placement when swallow unsafe
- Dietary supplementation
Speech and communication
- Regular assessment
- Voice banking
- AAC devices
- Communication partner training
Physical therapy
- Range of motion
- Transfer assistance
- Fall prevention
- Equipment provision
Experimental Therapies
| Approach | Status | Target |
|----------|--------|--------|
| C9orf72 ASO | Phase 1/2 trials | C9orf72 expansion |
| SOD1 ASO (tofersen) | Approved (2023) | SOD1 mutations |
| FUS ASO | Phase 1/2 trials | FUS mutations |
| Stem cell therapy | Phase 1/2 trials | Motor neuron replacement |
| Gene therapy | Various trials | Multiple |
Prognosis
Survival Statistics
- Median survival: 2-4 years from symptom onset
- 5-year survival: 10-20%
- 10-year survival: 2-5%
- 20-year survival: <1%
Prognostic Factors
| Factor | Effect |
|--------|--------|
| Younger age at onset | Better prognosis |
| Limb onset vs. bulbar | Better prognosis |
| Longer diagnostic delay | Better prognosis |
| Preserved respiratory function | Better prognosis |
| C9orf72 expansion | Variable |
| SOD1 mutations | Variable |
Causes of Death
- Respiratory failure (most common): 50-60%
- Pneumonia/aspiration: 20-30%
- Cardiovascular: 10-15%
- Cachexia: 5-10%
- Pulmonary embolism: 5%
Research Directions
Biomarker Development
- Neurofilaments: NfL, pNfH for diagnosis/prognosis
- Genetic markers: C9orf72, others
- Imaging: MRI, PET biomarkers
- Electrophysiology: Quantitative EMG markers
Clinical Trials
Active areas:
- Gene-targeted therapies
- Combination approaches
- Symptom-specific interventions
- Biomarker-driven trials
Emerging Concepts
- Recognition of ALS-FTD spectrum
- Precision medicine approaches
- Early intervention strategies
- Multi-omics integration
- [Amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis) (overview)
- [Bulbar amyotrophic lateral sclerosis](/diseases/bulbar-amyotrophic-lateral-sclerosis)
- [Primary lateral sclerosis](/diseases/primary-lateral-sclerosis)
- [Progressive muscular atrophy](/diseases/progressive-muscular-atrophy)
- [Kennedy disease](/diseases/kennedy-disease)
- [Frontotemporal dementia](/diseases/frontotemporal-dementia)
See Also
- [Cervical spondylotic myelopathy](/diseases/cervical-spondylotic-myelopathy)
- [Multifocal motor neuropathy](/diseases/multifocal-motor-neuropathy)
- [Kennedy disease](/diseases/kennedy-disease)
- [Myasthenia gravis](/diseases/myasthenia-gravis)
- [Spinal muscular atrophy](/diseases/spinal-muscular-atrophy)
- [Hereditary spastic paraplegia](/diseases/hereditary-spastic-paraplegia)
- [Toxic neuropathy](/diseases/toxic-neuropathy)
- [Amyotrophic lateral sclerosis](/diseases/amyotrophic-lateral-sclerosis)
- [Bulbar amyotrophic lateral sclerosis](/diseases/bulbar-amyotrophic-lateral-sclerosis)
- [Primary lateral sclerosis](/diseases/primary-lateral-sclerosis)
External Links
- [PubMed](https://pubmed.ncbi.nlm.nih.gov/)
- [KEGG Pathways](https://www.genome.jp/kegg/pathway.html)
Recent Research
This section needs to be populated with recent publications.
Key Research Directions
- ALS genetics and biomarkers
- Neuroprotective therapeutic approaches
- Clinical trial updates
References
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[^1]: [Reference missing - citation needed]