Amyotrophic Lateral Sclerosis - How to Diagnose

ALS Diagnosis Guide: Clinical Signs, EMG, Imaging & Genetic Testing

Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease which targets nerve cells that control muscle movement. It usually starts subtly but progresses quickly, causing the loss of motor ability and, eventually, respiratory arrest.

Nevertheless, since ALS has symptoms common to a wide range of neurological disorders, making a timely and correct diagnosis has become one of the most significant challenges. This article outlines the diagnostic approach to ALS, emphasising the importance of specialised testing and medical support.

What Triggers the Need for ALS Testing?

ALS usually starts with muscle weakness, twitching, or stiffness. When patients present with such symptoms, most especially when they are localised (such as in the hand or leg) and gradually get worse, neurologists start investigations to find out whether the cause is ALS or another neuromuscular disorder.

Warning signs are:

• Persistent muscle fasciculations (twitches)
• Muscle atrophy
• Progressive weakness without pain
• Difficulty speaking, swallowing, or breathing
   

Such nonspecific symptoms require a thorough work-up to distinguish between ALS and such disorders as multiple sclerosis, myasthenia gravis, or peripheral neuropathy.

Clinical Examination and History Review

Initial diagnosis of ALS encompasses a physical examination and an in-depth medical history. Neurologists assess:

• Upper motor neurone (UMN) signs: Enhanced deep tendon reflexes, spasticity, and pathological reflexes (e.g., Babinski sign)
• Lower motor neurone (LMN) signs: Fasciculations, muscle atrophy and weakness
• Pattern of progression: Symptom spreads throughout body parts, especially the mouth, limbs and trunk
• Speech and swallowing difficulties: Bulbar involvement is a key indicator.
   

Clinical assessment alone is not sufficient to diagnose ALS, but it can help direct additional testing by providing a restricted diagnostic focus.

Electromyography (EMG) and Nerve Conduction Studies

Electromyography (EMG) is one of the most important diagnostic tools for ALS. EMG assesses the electrical activity of muscles and can detect patterns consistent with motor neurone degeneration.

EMG usually reveals fibrillation potentials, positive sharp waves and fasciculations consistent with denervation and reinnervation. Such tendencies in various regions (e.g., limbs, tongue, diaphragm) indicate ALS.

NCS, when done together with EMG, assesses the functioning of peripheral nerves and aids in the elimination of other possible conditions, such as neuropathies or demyelinating diseases.

Magnetic Resonance Imaging (MRI) to Rule Out Mimics

MRI is not used to confirm ALS but is essential to rule out structural conditions that mimic its symptoms, such as:

• Spinal cord compression
• Brainstem tumours
• Cervical spondylotic myelopathy
• Multiple sclerosis
   

Normal imaging results, when combined with clinical and EMG evidence, support an ALS diagnosis.

Blood and Laboratory Tests

To exclude treatable conditions that can resemble ALS, blood tests are typically conducted:

• Thyroid function tests
• Vitamin B12 and folate levels
• HIV and syphilis serologies
• Autoimmune markers (ANA, anti-GM1 antibodies)
• Heavy metal screening is indicated
   

While none of these confirm ALS, they help eliminate alternative explanations for motor symptoms.

Lumbar Puncture and Cerebrospinal Fluid Analysis

Neurologists may perform a lumbar puncture in certain cases to examine the cerebrospinal fluid (CSF). This is often done to rule out:

• Chronic Inflammatory Demyelinating Polyneuropathy (CIDP)
• Multiple sclerosis
• Infections of the nervous system
   

A normal CSF profile, particularly with elevated EMG findings and clinical features, leans the diagnosis further toward ALS.

Revised El Escorial Criteria for ALS Diagnosis

Neurologists rely on the Revised El Escorial Criteria to formalise ALS diagnosis, which assesses the presence of upper and lower motor neurone signs across different body regions. ALS is categorised as:

• Definite ALS: Upper and lower motor neurone signs in at least three regions
• Probable ALS: Signs in at least two areas with some upper motor neurone findings
• Possible ALS: Signs confined to one region
   

This classification aids in both diagnosis and inclusion in clinical trials.

The Role of Genetic Testing

Approximately 5 to 10% of ALS cases are familial. Mutations in genes like C9ORF72, SOD1, and FUS are associated with familial ALS. While not routinely performed in all patients, it can help:

• Confirm diagnosis in familial cases
• Support future therapeutic decisions or trial eligibility
   

Assessing Functional Progression

Once ALS is diagnosed, measures like the ALS Functional Rating Scale-Revised (ALSFRS-R) and staging systems (King’s and MiToS) are used to assess disability level and progression. These tools guide therapeutic decisions and trial eligibility.

Why Early Diagnosis Matters

ALS progresses rapidly, and early diagnosis allows for:

• Timely intervention: Including the use of riluzole and edaravone to slow progression
• Nutritional and respiratory planning
• Access to clinical trials
• Psychological support and palliative care preparation
   

Furthermore, early confirmation empowers patients to make critical decisions about work, mobility aids, and long-term care.

Financial and Insurance Considerations in ALS Diagnosis

Diagnosing ALS involves extensive testing, including EMG, MRI, lab evaluations, and specialist consultations, which can incur significant expenses. Without sufficient insurance coverage, the diagnostic journey can become financially burdensome.

Plans like Star Health Insurance can help cover these costs, ensuring patients get timely access to diagnostic procedures, neurologist consultations, and related services without unnecessary delays. Given the urgency of managing progressive conditions like ALS, comprehensive insurance plays a crucial role in facilitating faster diagnosis and intervention.

Diagnosing amyotrophic lateral sclerosis requires a systematic, multi-step approach that integrates clinical evaluation, EMG findings, imaging, and the exclusion of other conditions.

While no single test can confirm ALS outright, the convergence of clinical and diagnostic data is critical for accuracy. Early recognition, supported by strong health insurance such as Star Health, ensures patients receive timely care, appropriate planning, and access to evolving therapies.