What are the diagnostic tests and management options for Amyotrophic Lateral Sclerosis (ALS)?

Diagnostic Testing and Management for Amyotrophic Lateral Sclerosis (ALS)

Electromyography (EMG) and nerve conduction studies (NCS) are the cornerstone diagnostic tests for ALS, as they can detect lower motor neuron degeneration and help distinguish ALS from other conditions. 1

Diagnostic Approach

Primary Diagnostic Tests

• EMG/NCS are essential for diagnosing ALS, revealing active neurogenic changes (fibrillation potentials, positive sharp waves, and fasciculation potentials) over wide territories of the body 1, 2
• MRI of the brain without IV contrast is recommended for initial imaging to exclude other conditions with similar clinical presentations 1, 3
• MRI of the spine without IV contrast may be appropriate to exclude structural, infectious, or neoplastic etiologies that can mimic motor neuron disease 1, 3

Laboratory Tests to Exclude Treatable Mimics

• Complete blood count to evaluate for infectious or inflammatory conditions 1, 3
• Blood chemistry profile including glucose, electrolytes, kidney function, and liver enzymes 3
• Thyroid function tests to rule out thyroid disorders that can cause weakness 1, 3
• Vitamin B12, folate, and vitamin E levels to exclude deficiencies that can cause neurological symptoms 1, 3
• Serum protein electrophoresis to rule out paraproteinemic neuropathies 1, 3
• Anti-ganglioside antibodies to exclude immune-mediated motor neuropathies 1, 3
• Paraneoplastic antibody panel to exclude paraneoplastic syndromes 1, 3
• Anti-acetylcholine receptor and anti-MuSK antibodies to rule out myasthenia gravis 1, 3

Additional Diagnostic Tests

• Cerebrospinal fluid analysis to exclude infectious, inflammatory, or neoplastic causes 1, 3
• Genetic testing for ALS-associated genes (e.g., C9orf72, SOD1, FUS, TARDBP), especially in cases with family history 1, 3, 4

Swallowing Evaluation

• Structured questionnaires (e.g., EAT-10) can identify patients with unsafe airway protection (sensitivity 86%, specificity 76%) 5, 3
• Volume-Viscosity Swallow Test (V-VST) has high sensitivity (92%) and specificity (80%) for detecting dysphagia in ALS patients 5, 3
• Videofluoroscopy is strongly recommended in the clinical evaluation of dysphagia at diagnosis of ALS (Grade of recommendation: GPP with 95% agreement) 5
• Fiberoptic endoscopic evaluation of swallowing (FEES) can identify impaired chewing, tongue muscle deficit, and other swallowing abnormalities 5

Neurological Examination Findings

• Evaluate lip closure and evidence of saliva pooling, with particular attention to bulbar involvement 6
• Assess tongue strength, mobility, and tone, looking for atrophy and fasciculations 6
• Examine chewing capacity and jaw strength 6
• Test palatal movement in response to tactile stimulation 6
• Evaluate the quality and strength of cough 6
• Assess phonation and speech function, including dysarthria 6
• Test for hyperreflexia in all limbs 6
• Assess respiratory muscle strength, including forced vital capacity if available 6
• Look for use of accessory respiratory muscles 6

Management Approach

FDA-Approved Medications

• Riluzole is indicated for the treatment of ALS 7
• Clinical studies demonstrated that riluzole 50 mg twice daily extends survival time to tracheostomy or death by approximately 60-90 days compared to placebo 7
• Edaravone, a free radical scavenger, is also FDA-approved for ALS treatment 8

Supportive Care

• Regular swallowing evaluations (recommended every 3 months) to monitor dysphagia progression 3, 6
• Non-invasive ventilation prolongs survival and improves quality of life 4
• Nutritional support is essential for patients with dysphagia and weight loss 3
• Early referral to palliative services to establish relationships with staff and address end-of-life issues before communication becomes limited 3

Prognosis

• Mean survival of typical ALS patients is 3-5 years after symptom onset 3, 4
• Only 5-10% of patients live longer than 10 years 3
• Respiratory failure due to respiratory muscle weakness is the most common cause of death 3, 4

Common Pitfalls in Diagnosis

• Many physicians, including neurologists, miss the diagnosis due to lack of knowledge about ALS or diagnostic difficulty 9
• The differential diagnosis must exclude non-motor neuron diseases and other adult-onset motor neuron diseases with restricted presentations 9
• Although the diagnosis of ALS remains primarily clinical, laboratory testing is crucial to exclude other diseases and confirm the diagnosis 9, 10
• Early diagnosis is essential for timely intervention, but can only be achieved when physicians include ALS in their differential diagnosis 9