Is it possible to misdiagnose ALS?

Errors are possible in any human action, including the diagnosis of ALS. One difficulty in diagnosing ALS is that the diagnosis is based on a specific combination of symptoms and test findings. ALS is a “diagnostic mosaic,” in which the diagnostic picture is composed of individual components (a mosaic). Various features of the clinical examination findings, the course of the disease, and various additional diagnostic tests come together to form the overall picture of an ALS diagnosis. Recognizing and interpreting the individual findings requires specialization and experience in ALS diagnostics.

Despite this specialization, a misdiagnosis can still occur. In complex diagnostic situations, even specialized neurologists with extensive experience in ALS may be unable to make a definitive diagnosis, and several differential diagnoses may be possible (e.g., distinguishing ALS from spinal muscular atrophy or immunoneuropathy). In such cases, open communication about the diagnostic uncertainty (and the associated probability of error) is advisable. This ensures that the patient is informed of the existing uncertainty and that the relationship of trust between doctor and patient is maintained—despite the diagnostic ambiguity. Overall, however, the probability of error in diagnosing ALS is very low, especially when the patient is seen at a specialized outpatient clinic.