How is ALS primarily diagnosed?

Amyotrophic lateral sclerosis (ALS) is primarily diagnosed based on clinical criteria, specifically the Escorial criteria, which encompass the progression of symptoms and confirm the presence of upper and lower motor neuron signs. The Escorial criteria categorize the diagnosis into probable, possible, and definite ALS, based on clinical examination and the identification of neurodegeneration in the upper and lower motor neurons.

While MRI scans can be useful in ruling out other conditions that may mimic ALS, they are not definitive for diagnosing ALS itself, as there are no specific findings on an MRI that are exclusive to ALS. Blood tests can also help exclude other conditions or monitor for genetic mutations associated with ALS, but they do not provide a diagnosis of ALS. Family history may be relevant in understanding the familial forms of ALS, but alone, it does not establish the diagnosis of the disease. Thus, the reliance on the established Escorial criteria makes it the primary method for diagnosing ALS.