From the Guidelines
Diagnosing ALS requires a comprehensive neurological evaluation, including electromyography (EMG) and nerve conduction studies, as well as MRI scans of the brain and spinal cord to exclude other conditions, as stated in the 2020 study by the Journal of the American College of Radiology 1. The diagnosis of ALS typically begins with a detailed medical history and physical examination by a neurologist who specializes in neuromuscular disorders. Several tests are used to rule out other conditions and support an ALS diagnosis, including:
- Electromyography (EMG) to measure electrical activity in muscles
- Nerve conduction studies to assess nerve function
- MRI scans of the brain and spinal cord to exclude other conditions like tumors or spinal cord compression
- Blood and urine tests to rule out other diseases
- Sometimes a muscle biopsy or spinal tap The El Escorial criteria, a standardized diagnostic approach, is often used to classify ALS cases as definite, probable, possible, or suspected based on the presence of upper and lower motor neuron signs in multiple body regions, as mentioned in the study 1. Early symptoms to watch for include:
- Muscle weakness
- Twitching
- Cramping
- Stiffness
- Slurred speech
- Difficulty swallowing Since ALS is a diagnosis of exclusion, the process may take several months as other conditions with similar symptoms must be systematically ruled out before confirming an ALS diagnosis, as noted in the 2020 study by the Journal of the American College of Radiology 2. The most common MRI finding in the brain in ALS is abnormal signal on T2/FLAIR or proton density–weighted images, which can be seen anywhere within the cortico-spinal tracts, as stated in the study 2. T2*-weighted imaging or susceptibility-weighted imaging is also important in the evaluation of suspected ALS because abnormal hypointensity in the precentral gyrus and gray matter has been noted to be highly sensitive and specific for ALS, as mentioned in the study 2. MRI of the spine without IV contrast is often normal early in the disease course of ALS, but may be useful in certain clinical circumstances to exclude structural, infectious, or neoplastic etiologies of the spine that can mimic motor neuron disease, as noted in the study 2.
From the Research
Diagnostic Criteria for ALS
The diagnosis of ALS is based on the El Escorial criteria, which require the presence of progressive motor symptoms, such as muscle weakness, muscle atrophy, and spasticity 3. The differential diagnosis must exclude non-motor neuron diseases and other adult-onset motor neuron diseases with restricted presentations.
Laboratory Tests for ALS
Laboratory tests, such as EMG and nerve conduction studies, MRI and CT of the spine and brain, identification of biochemical markers in blood and CSF, and muscle or nerve biopsy, can be used to exclude other diseases and confirm the diagnosis of ALS 3. Genetic testing can identify gene defects in some types of familial ALS and in certain other inherited motor neuron diseases that mimic ALS.
Key Factors in Diagnosing ALS
Key factors in diagnosing ALS include:
- Progressive motor symptoms, such as muscle weakness, muscle atrophy, and spasticity
- Exclusion of non-motor neuron diseases and other adult-onset motor neuron diseases with restricted presentations
- Use of laboratory tests, such as EMG and nerve conduction studies, to confirm the diagnosis
- Genetic testing to identify gene defects in some types of familial ALS
Challenges in Diagnosing ALS
Challenges in diagnosing ALS include:
- Lack of knowledge about ALS among physicians, including neurologists
- Diagnostic difficulty due to the variability of symptoms and the presence of other diseases with similar symptoms
- Need for a comprehensive diagnostic approach, including laboratory tests and genetic testing, to confirm the diagnosis 3, 4
Importance of Early Diagnosis
Early diagnosis of ALS is crucial for optimal treatment and care, as it allows for the initiation of treatment with riluzole, which has been shown to slow the progression of the disease and extend survival 5, 6, 7.