How common is a misdiagnosis of ALS?

In a very small proportion of patients, diagnosis is difficult. Diagnostic difficulties arise primarily when there is an overlap of several diseases, the progression of the disease is unusual, or ALS presents with unusual symptoms. Conversely, in very rare cases, other neurological disorders may give the impression of ALS and only turn out to be a different diagnosis as the condition progresses (known as “ALS mimic syndrome”).

The risk of a misdiagnosis is particularly high when two or more neurological disorders coexist and it is initially unclear which of the disorders is responsible for the symptoms (e.g., ALS in combination with disc disease, which is common in the general population). In addition, there are rare combinations of conditions that are not yet fully understood (e.g., ALS combined with MS, spinal cord changes, Parkinson’s symptoms, hearing loss, muscle disorders, and other complex conditions). Overall, misdiagnosis of ALS is very rare when the disease presents with typical symptoms.