How is amyotrophic lateral sclerosis (ALS) diagnosed?

From the Guidelines

Diagnosing amyotrophic lateral sclerosis (ALS) requires a comprehensive clinical and neurological evaluation, including the assessment of dysphagia, as well as the use of various diagnostic tests such as electromyography (EMG), nerve conduction studies, and imaging tests like MRI. The diagnostic process for ALS is complex and involves ruling out other conditions with similar symptoms. According to the espen guideline on clinical nutrition in neurology 1, a comprehensive clinical evaluation should include the assessment of dysphagia, which is a common symptom in ALS patients, even in the absence of bulbar symptoms.

The clinical evaluation of dysphagia should include the assessment of lip closure, tongue strength, mobility and tone, chewing capacity, palatal movement, and phoniatric function, as well as the quality and strength of the cough 1. Instrumental assessment of dysphagia, such as videofluoroscopy (VFS) or fiberoptic endoscopic evaluation of swallowing (FEES), may also be performed in patients with symptoms of dysphagia.

Some key points to consider in the diagnosis of ALS include:

• A detailed medical history and neurological examination to identify characteristic signs of upper and lower motor neuron damage
• Electromyography (EMG) and nerve conduction studies to detect abnormalities consistent with ALS
• Blood and urine tests to exclude metabolic or toxic causes of symptoms
• Magnetic resonance imaging (MRI) of the brain and spinal cord to rule out conditions that might mimic ALS symptoms
• The use of clinical severity scales, such as the ALS Functional Rating Scale-Revised (ALSFRS-R) or the ALS Swallowing Severity Scale (ALSSS), to assess the presence and severity of dysphagia and other symptoms 1.

The diagnosis of ALS should be based on a comprehensive evaluation of the patient's symptoms, medical history, and diagnostic test results, and should be made in accordance with established diagnostic guidelines, such as the El Escorial criteria.

From the Research

Diagnosis of Amyotrophic Lateral Sclerosis (ALS)

The diagnosis of ALS is suggested by clinical examination that reveals both upper and lower motor neuron failure 2. The following are key points to consider in diagnosing ALS:

• Progressive loss of motor neurons causes ALS, with patients complaining of progressive weakness in the distal limbs 2
• Weakness may manifest in any body segment (bulbar, cervical, thoracic, or lumbosacral) 2
• Formal diagnostic criteria have been developed and validated 2
• Nerve conduction and electromyography studies improve diagnostic sensitivity and exclude some alternate, treatable diagnoses 2
• Conventional imaging studies and laboratory evaluation refute other diseases that may masquerade as ALS 2

Clinical Presentation

The clinical presentation of ALS includes:

• Progressive muscle weakness and wasting 3
• Failure of respiratory muscles typically limits survival to 2-5 years after disease onset 3
• Extra-motor manifestations such as changes in behaviour, executive dysfunction, and language problems 3
• In 10%-15% of patients, these problems are severe enough to meet the clinical criteria of frontotemporal dementia (FTD) 3

Diagnostic Evaluation

The diagnostic evaluation of ALS includes:

• Forced vital capacity (FVC) is commonly used to evaluate respiratory status 4
• Maximal pressures measured at the mouth are useful for excluding weakness if they are normal 4
• Invasive testing, such as measurement of transdiaphragmatic pressure, provides an accurate measure of inspiratory strength 4
• Supportive respiratory techniques such as mechanically assisted coughing, non-invasive ventilation, and tracheostomy with mechanical ventilation 4