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 affecting both upper and lower motor neurons, with approximately 25% of patients experiencing bulbar-onset disease characterized by speech and swallowing difficulties, while the remaining 75% present with limb-onset weakness. 1, 2

Motor Symptoms

Upper Motor Neuron Signs

• Hyperreflexia (increased deep tendon reflexes throughout affected regions) 1, 3
• Spasticity (muscle stiffness and increased tone), present in approximately 47% of cases 1, 2
• Hypertonicity affecting movement coordination 1

Lower Motor Neuron Signs

• Muscle fasciculations (visible muscle twitching under the skin), occurring in over 90% of patients 1, 2
• Progressive muscle weakness affecting 100% of cases, typically starting focally and spreading to adjacent body regions 4, 2
• Muscle atrophy (wasting), present in over 90% of patients 1, 2

Bulbar Symptoms (Present in 25-33% at Onset)

Speech and Communication Deficits

• Dysarthria (slurred or difficult speech) due to weakness of muscles controlling articulation 5, 3
• Nasal voice quality from reduced soft-palate closure 5
• Progressive loss of verbal communication ability, eventually imprisoning patients in isolation 6

Swallowing Dysfunction (Dysphagia)

• Difficulty managing food in the mouth with impaired bolus formation 5
• Prolonged meal times and fatigue during eating as early manifestations 5
• Difficulty chewing certain food textures 5
• Delayed swallowing initiation and impaired bolus transport from oral cavity to pharynx 7, 5
• Nasal regurgitation of food and liquids due to soft-palate weakness 5
• Food trapping in buccal sulcus from poor lip seal 5
• Increased aspiration risk, with aspiration pneumonia occurring in 11.4-13% of cases 7, 5

Secretion Management Problems

• Sialorrhea (drooling) resulting from inability to manage saliva due to impaired swallowing and poor lip seal 5, 8

Limb-Onset Symptoms (Present in 68% at Onset)

Upper Extremity Manifestations

• Problems with dexterity and fine motor tasks 8
• Hand weakness affecting grip strength 2
• Muscle wasting in hands and forearms 4

Lower Extremity Manifestations

• Gait difficulties from leg weakness 8
• Foot drop and tripping 4
• Progressive leg weakness spreading from one limb to contralateral limb 2

Respiratory Symptoms

• Progressive respiratory muscle weakness affecting all patients eventually 3
• Dyspnea (shortness of breath), particularly with exertion initially 3
• Orthopnea (difficulty breathing when lying flat) 3
• Respiratory failure as the ultimate cause of death in nearly all ALS patients, typically within 3-5 years of diagnosis 1, 3

Cognitive and Behavioral Symptoms

• Executive dysfunction present in up to 50% of cases 4
• Behavioral changes including apathy, disinhibition, and loss of empathy 4
• Language problems affecting word-finding and comprehension 4
• Frontotemporal dementia meeting full clinical criteria in 10-15% of patients 4
• Emotional lability (pseudobulbar affect) with inappropriate laughing or crying in up to 60% of cases 2

Pattern of Progression

The disease typically follows a predictable spreading pattern: weakness beginning in one limb tends to spread to the contralateral limb, then to other body regions, with bulbar symptoms eventually developing in most patients regardless of onset site 2. Lower extremity onset (36% of cases) tends to progress to the contralateral leg, upper extremity onset (32%) spreads similarly, and bulbar onset (25%) typically progresses to upper extremity involvement 2.

Preserved Functions (Critical Distinguishing Features)

• Sphincter control remains intact (bladder and bowel function preserved) 8
• Sensory function completely preserved (no numbness or sensory loss) 8
• Intellectual abilities maintained in 50-85% of patients 8
• Eye movements typically spared until very late stages 1
• Skin integrity preserved 8

Clinical Pitfalls to Recognize

Silent aspiration can occur without observable clinical signs or patient complaints, making instrumental swallowing assessment essential even in asymptomatic patients 7, 1. Approximately 40% of patients have cognitive impairment that may affect treatment adherence and decision-making capacity, requiring early cognitive screening 1, 9. The disease progresses at variable rates, with 25% of patients experiencing plateaus lasting 9 months or longer, though the overall trajectory remains relentlessly progressive 2.