What are the signs and symptoms of amyotrophic lateral sclerosis (ALS)?

Signs and Symptoms of Amyotrophic Lateral Sclerosis (ALS)

ALS presents with progressive muscle weakness, atrophy, and fasciculations combined with hyperreflexia, while characteristically preserving sphincter control, sensory function, intellectual abilities, and skin integrity. 1

Clinical Presentation Patterns by Site of Onset

ALS manifests in two primary patterns based on initial symptom location:

Limb-Onset (Spinal) ALS (65-75% of cases)

• Progressive muscle weakness in arms or legs as the primary manifestation 2
• Muscle atrophy and fasciculations affecting the extremities, present in over 90% of cases 3
• Hyperreflexia (exaggerated reflexes) indicating upper motor neuron involvement 1
• Spasticity (muscle stiffness and rigidity) occurs in approximately 47% of patients 3
• Asymmetric weakness is common, with a typical progression pattern: if right leg onset, left leg follows; if right arm onset, left arm follows 3

Bulbar-Onset ALS (25-35% of cases)

• Dysarthria (speech difficulty) develops in approximately 80% of bulbar-onset patients 2, 1
• Dysphagia (swallowing difficulty) affects nearly 80% of bulbar-onset cases and eventually develops in up to 30% at diagnosis across all ALS types, with nearly universal progression 1
• Sialorrhea (excessive drooling) due to impaired swallowing of saliva 4
• Nasal regurgitation from soft palate weakness 1, 4
• Difficulty with chewing and oral preparation of food 1
• Prolonged meal times leading to muscular fatigue during eating 1
• Median survival is significantly shorter at 25-28 months from symptom onset, compared to 44 months for spinal-onset patients 1

Core Motor Manifestations

Upper Motor Neuron Signs

• Hypertonicity (increased muscle tone) 4
• Hyperreflexia (exaggerated deep tendon reflexes) 4
• Spasticity affecting approximately 47% of patients 3

Lower Motor Neuron Signs

• Muscle fasciculations (visible muscle twitching) present in over 90% of cases 3
• Progressive muscle weakness affecting 100% of cases 3
• Muscle atrophy (wasting) occurring in over 90% of patients 3

Respiratory Manifestations

• Morning headaches indicating nocturnal hypoventilation 1
• Daytime sleepiness from respiratory muscle weakness 1
• Disturbed sleep due to respiratory compromise 1
• Aspiration pneumonia occurs in 11.4-13% of bulbar ALS cases and represents a leading cause of mortality 1
• Respiratory failure is the most common cause of death 4

Swallowing-Specific Abnormalities (Videofluoroscopic Findings)

• Delayed bolus transport from oral cavity to pharynx is the most frequent finding 1
• Decreased pharyngeal contraction and low tongue driving forces 1
• Oral residue affects all patients regardless of bulbar symptom presence 1
• Pharyngeal residue develops universally in ALS patients 1
• Silent aspiration can occur without observable clinical signs, detectable only by instrumental evaluation 1, 4
• Impaired bolus preparation/mastication in bulbar symptoms-positive patients 5
• Impaired laryngeal elevation, anterior hyoid excursion, and tongue base retraction when bulbar symptoms are present 5

Cognitive and Behavioral Manifestations

• Cognitive dysfunction occurs in 20-50% of ALS cases 2
• Frontotemporal dementia (FTD) develops in 10-15% of patients, severe enough to meet clinical criteria 6
• Behavioral changes including apathy and personality alterations 2
• Executive dysfunction affecting judgment, problem-solving, and reasoning 2
• Language problems including word-finding difficulty and speech impairments 2
• Emotional lability (pseudobulbar affect) occurs in up to 60% of cases 3

Nutritional and Metabolic Manifestations

• Weight loss develops in 0-21% of patients at diagnosis and worsens progressively 1
• Malnutrition with weight loss >5% doubling the risk of death 1
• Anorexia attributed to psychosocial distress, depression, and polypharmacy 1
• Paradoxically increased energy requirements due to increased work of breathing, lung infections, and metabolic factors 1
• Constipation from weakness of abdominal and pelvic muscles, limiting fluid and fiber intake 1
• Muscular fatigue during eating requiring prolonged meal times 1

Pattern of Disease Progression

• Focal onset with subsequent spread to different body regions 6
• Predictable progression pattern based on area of onset: lower limb onset tends to progress to contralateral lower limb, then upper limbs; upper limb onset follows similar contralateral pattern 3
• Sparing of body parts can occur for follow-up times approaching 3 years in significant numbers of patients 3
• Plateau periods lasting a minimum of 9 months occur in approximately 25% of patients, though the majority experience significantly linear deterioration 3

Critical Pitfalls to Recognize

• Silent aspiration without clinical signs requires instrumental evaluation (videofluoroscopy or FEES) for detection 1, 4
• Atypical presentations such as asymmetric or predominantly proximal/distal weakness can delay diagnosis 2
• Severe diffuse pain may precede weakness, mimicking other conditions 2
• Cognitive impairment may be subtle initially but affects up to 40% of patients and impacts treatment decisions 4
• Videofluoroscopy can reveal swallowing alterations in asymptomatic ALS patients, emphasizing the need for early instrumental assessment 5