Amyotrophic lateral sclerosis (ALS)
Amyotrophic lateral sclerosis is a progressive motor neuron disease combining upper and lower motor neuron signs without sensory loss, diagnosed by combining clinical examination with EMG evidence of lower motor neuron involvement in at least two body regions after mimics are excluded. Riluzole and edaravone offer modest survival benefit; management is otherwise multidisciplinary and supportive, including noninvasive ventilation and nutritional support.
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What this article covers
- Overview
Definition: amyotrophic lateral sclerosis (ALS) is a neurodegenerative motor neuron disease that causes progressive weakness, muscle atrophy, and early death, reflecting combined degeneration of upper and lower motor neurons.
- Epidemiology
Motor neuron disease spectrum: ALS is the most commonly encountered motor neuron disease in adult neurology practice and the prototype of combined upper and lower motor neuron degeneration.
- Risk factors
Coexisting frontotemporal disease: a diagnosis of behavioral-variant FTD is a risk marker for concurrent or subsequent ALS, and vice versa, given their shared neurodegenerative pathology.
- Pathophysiology
Combined motor neuron degeneration: ALS reflects progressive loss of both upper motor neurons (corticospinal tract) and lower motor neurons (anterior horn cells and their peripheral axons), producing…
- Clinical features
Asymmetric limb-onset weakness: many patients present with asymmetric distal extremity weakness that begins focally and spreads.
- Differential diagnosis
Multifocal motor neuropathy: a treatable ALS mimic that features severe weakness with only minimal atrophy, an absence of any upper motor neuron signs, and electromyography (EMG) evidence of motor…
- Diagnosis
Clinical diagnosis anchored on combined upper motor neuron (UMN) and lower motor neuron (LMN) signs: ALS is diagnosed based on clinical evidence of both UMN and LMN signs on examination together with…
- Management
First, confirm the diagnosis and refer for multidisciplinary care: management of ALS is supportive and should involve a multidisciplinary team (neurology, pulmonology, nutrition, physical and…
- Complications
Respiratory failure: progressive respiratory muscle weakness is the major life-threatening complication and the eventual cause of death in most patients if not managed with ventilatory support.
- Prognosis
Early death: ALS is characterized by progressive weakness, atrophy, and early death, reflecting the relentless nature of combined upper and lower motor neuron degeneration.
- Prevention
No established primary prevention: there are no known modifiable exposures proven to prevent ALS, so prevention efforts focus on early recognition and secondary prevention of complications.
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