Diagnosing Amyotrophic Lateral Sclerosis (ALS)

Clinical Diagnostic Requirements

• The American Academy of Neurology recommends that the diagnosis of ALS requires demonstrating both upper and lower motor neuron degeneration through clinical examination combined with electromyography (EMG) and nerve conduction studies, while systematically excluding treatable conditions that mimic ALS through comprehensive laboratory testing and neuroimaging 1, 2
• The diagnosis is fundamentally clinical and requires three key elements: upper motor neuron signs (hypertonicity, hyperreflexia, and spasticity), lower motor neuron signs (muscle fasciculations, weakness, and atrophy), and progressive spread of symptoms through different body regions over time 1, 3

Mandatory Electrophysiological Testing

• EMG and nerve conduction velocity studies are the cornerstone diagnostic tests and are mandatory for diagnosing ALS, detecting lower motor neuron degeneration and distinguishing ALS from other conditions 1, 2

Essential Neuroimaging

• The American College of Radiology recommends that MRI brain without IV contrast is the initial imaging study of choice to exclude structural lesions, inflammatory conditions, and other diseases that mimic ALS 1, 2
• Supportive (but not diagnostic) findings include abnormal T2/FLAIR signal in corticospinal tracts, particularly in the posterior limb of internal capsule and cerebral peduncles, and abnormal hypointensity in precentral gyrus on T2*-weighted or susceptibility-weighted imaging 1, 2

Comprehensive Laboratory Workup to Exclude Mimics

• A comprehensive metabolic and immunologic workup is essential to exclude treatable conditions that present with similar symptoms, including complete blood count (CBC), blood chemistry profile, thyroid function tests, vitamin B12, folate, and vitamin E levels, serum protein electrophoresis, anti-ganglioside antibodies, and paraneoplastic antibody panel 1, 2

Cerebrospinal Fluid Analysis

• CSF examination should include cell count, protein, glucose, IgG index, oligoclonal bands, and cytology to exclude infectious, inflammatory, or neoplastic causes, with marked pleocytosis (>50 cells/μL) suggesting an alternative diagnosis 1, 2

Dysphagia Screening at Diagnosis

• The European Society for Clinical Nutrition and Metabolism recommends screening for dysphagia at diagnosis and every 3 months during follow-up, even in patients without bulbar symptoms, using structured questionnaires (EAT-10) and Volume-Viscosity Swallow Test (V-VST) 1, 4
• Videofluoroscopy should be performed at diagnosis to detect early signs of dysphagia and silent aspirations 1

Nutritional Screening at Diagnosis

• The European Society for Clinical Nutrition and Metabolism recommends screening for malnutrition (BMI, weight loss) at diagnosis and during follow-up every 3 months 4

Common Pitfalls to Avoid

• Silent aspiration can occur, necessitating objective dysphagia assessment 3