How reliable is an ALS diagnosis?

A diagnosis of ALS can be made with a high degree of certainty in the majority of those affected. The diagnosis is based on the medical history (a doctor-patient discussion to determine the medical history, which reveals the exact sequence of symptoms and complaints), the findings of the neurological examination (a physical examination by a neurologist), and electrophysiological testing (electroneurography and electromyography). In addition, magnetic resonance imaging (MRI) of the head and/or spinal cord is performed to confirm the diagnosis. In most cases, an analysis of thecerebrospinal fluid (CSF; “CSF” for short) is also required.

Not all tests are necessary for every patient to confirm a diagnosis of ALS. In most cases, diagnosing ALS poses no diagnostic challenge for an experienced neurologist. Only in exceptional cases (less than 10% of those affected) can the diagnosis be complex and difficult. In the majority of cases, the diagnosis can be considered definitive. Only in exceptional cases (less than 5%) are invasive diagnostic procedures (e.g., a muscle or nerve biopsy) necessary.

There is no laboratory test available to diagnose ALS. However, identifying molecules (biomarkers) in blood, cerebrospinal fluid (CSF), or other bodily fluids can further support and supplement the diagnosis and prognosis of ALS. The biomarker “neurofilament light chain” (NfL) has been used since 2017 in certain situations to confirm the diagnosis and in various research projects. Genetic testing can also aid in diagnosis. It is primarily available to patients with “familial ALS” (FALS).

Familial ALS (FALS) is diagnosed when several family members have ALS and the condition has a hereditary cause. In this case, genetic testing is available using a blood sample. In the majority of individuals with FALS, the causative gene can be identified through molecular genetic analysis. Overall, a combination of a physical examination and electrophysiological testing (electroneurography, EMG) can reliably confirm a diagnosis of ALS.