Amyotrophic Lateral Sclerosis: Symptoms, Causes & Treatment
ضمور الخلايا العصبية الحركية ALS
Amyotrophic lateral sclerosis (ALS) is a fatal progressive neurodegenerative disease destroying motor neurons, causing escalating muscle weakness, paralysis, and ultimately death, usually from respiratory failure.
What is Amyotrophic Lateral Sclerosis?
Amyotrophic lateral sclerosis (ALS), also known as Lou Gehrig's disease, is the most common and most devastating motor neuron disease in adults. It selectively and progressively destroys both upper motor neurons (UMN — cortical and corticospinal) and lower motor neurons (LMN — brainstem and spinal cord), producing the pathognomonic clinical combination of UMN signs (hyperreflexia, spasticity, Babinski sign) and LMN signs (fasciculations, atrophy, weakness). ALS affects 2–5 per 100,000 annually; mean onset age is 55–75 years.
Disease progression is relentlessly downhill: weakness typically begins focally (limb-onset in 70%, bulbar-onset in 30%) and spreads contiguously to involve all voluntary muscles, including those of respiration and swallowing. Crucially, cognitive and sensory function are usually preserved — patients remain mentally intact as their bodies fail them, a defining feature that profoundly shapes the palliative care approach. Median survival from symptom onset is 3 years; 10% survive beyond 10 years (notably Stephen Hawking). Death most commonly results from respiratory failure.
Familial ALS (10%) is caused by mutations in SOD1, C9orf72 (the most common — also causes frontotemporal dementia), FUS, or TARDBP. Sporadic ALS (90%) arises from complex gene-environment interactions involving glutamate excitotoxicity, mitochondrial dysfunction, neurofilament aggregation, and neuroinflammation. FDA-approved disease-modifying therapies: riluzole (anti-glutamatergic), edaravone (antioxidant), and tofersen (ASO targeting SOD1 mRNA) — all provide modest benefit. Multidisciplinary care (neurology, respiratory, gastroenterology, physiotherapy, speech therapy, palliative care) significantly extends quality of life and survival.
Symptoms
- Focal muscle weakness: foot drop, grip weakness, shoulder weakness (limb onset) or slurred speech/dysphagia (bulbar onset)
- Fasciculations: visible or palpable involuntary muscle twitching — an LMN hallmark
- Progressive muscle atrophy, particularly thenar eminence, interossei, tongue
- Dysarthria and dysphagia in bulbar-onset or as disease spreads
- Exertional dyspnea and reduced cough efficacy from respiratory muscle involvement
- UMN signs: hyperreflexia, clonus, spasticity, Babinski sign, pseudobulbar affect (inappropriate laughing/crying)
Causes
- 90% sporadic: unknown cause; complex interaction of genetic susceptibility and environmental exposure
- 10% familial: C9orf72 repeat expansion (most common ~40% of fALS), SOD1 mutations (~20%), FUS, TARDBP (TDP-43)
- Environmental associations: heavy metals, pesticides, agricultural work — epidemiological links, unconfirmed causation
- Cigarette smoking: relative risk ~1.5–2.0
- Military service and professional contact sports (CTE overlap under investigation)
Diagnosis
Diagnosis requires clinical evidence of combined UMN and LMN degeneration in multiple body regions, with progressive course and exclusion of other causes (revised El Escorial or Gold Coast criteria). EMG/NCS: confirms active and chronic LMN denervation across ≥2 body regions, distinguishes ALS from multifocal motor neuropathy. MRI brain and spine: excludes structural lesions, spondylotic myelopathy, foramen magnum compression. Comprehensive blood/CSF workup to exclude mimics: heavy metals, anti-GM1 antibodies, paraneoplastic, thyroid. Genetic testing: C9orf72 expansion, SOD1, FUS in all patients regardless of family history. Diagnosis typically takes 9–12 months from symptom onset due to the insidious mimics.
Treatment
No curative treatment exists. Disease-modifying therapies: riluzole (anti-glutamatergic; extends median survival ~3 months; oral); edaravone (antioxidant; slows ALSFRS-R functional decline; IV or oral); tofersen (antisense oligonucleotide targeting SOD1 mRNA; FDA approved 2023 for SOD1-ALS). Multidisciplinary ALS clinic care (neurology, respiratory, GI, PT, OT, SLP, social work, palliative) extends survival and significantly improves quality of life. Respiratory management: NIV (BiPAP) when FVC <50% — the single most life-prolonging intervention. Nutritional support: PEG tube when dysphagia threatens nutrition. Augmentative and alternative communication (AAC) devices. Palliative care integration from diagnosis.
Complications
- Respiratory failure — the primary cause of death; requires proactive ventilator planning
- Malnutrition and dehydration from progressive dysphagia
- Aspiration pneumonia from bulbar dysfunction
- Depression and anxiety — up to 50% of patients; PBA affects 20–50%
- Communication loss: total anarthria in bulbar-dominant ALS
Prevention
- No proven prevention for sporadic ALS
- Smoking cessation — the only modifiable environmental risk factor with consistent evidence
- Genetic counseling for families carrying SOD1, C9orf72, or other pathogenic mutations; pre-implantation genetic diagnosis is an option
- Clinical trial participation accelerates development of disease-modifying therapies
When to see a doctor
See a neurologist promptly for any progressive unexplained muscle weakness, visible fasciculations, worsening dysarthria or dysphagia, or exertional dyspnea without cardiopulmonary cause. Early diagnosis — though devastating — is vital: it opens access to disease-modifying therapy, clinical trials, multidisciplinary ALS clinic care, and early advance care planning while cognitive capacity is intact.