From suspicion to diagnosis: exploration strategy for suspected amyotrophic lateral sclerosis

Abstract

The diagnosis of amyotrophic lateral sclerosis (ALS) is based on evidence of upper and lower motor neuron degeneration in the bulbar, cervical, thoracic, and lumbar regions in a patient with progressive motor weakness, in the absence of differential diagnosis. Despite these well-defined criteria, ALS can be difficult to diagnose, given the wide variety of clinical phenotypes. Indeed, the central or peripheral location of the disease varies with a spectrum ranging from predominantly central to exclusively peripheral, symptoms can be extensive or limited to the limbs, bulbar area or respiratory muscles, and the duration of the disease may range from a few months to several decades. In the absence of a specific test, the diagnostic strategy relies on clinical, electrophysiological, biological and radiological investigations to confirm the disease and exclude ALS mimics. The main challenge is to establish a diagnosis based on robust clinical and paraclinical evidence without delaying treatment initiation by increasing the number of additional tests. This approach requires a thorough knowledge of the phenotypes of ALS and its main differential diagnoses.

Keywords: ALS mimics; Amyotrophic lateral sclerosis; Gold Coast criteria.

Figure 1.

Clinical phenotypes of ALS (initial presentation). ALS: amyotrophic lateral sclerosis, LMN: lower motor neuron, UMN: upper motor neuron.

Figure 2.

Diagnostic strategy for a patient with suspected ALS. AMN: adrenomyeloneuropathy, CIDP: chronic inflammatory demyelinating polyradiculoneuropathy, CNS: Central nervous system, CT CAP: CT scan chest abdomen pelvis, EMNG: electromyoneurography, HSP: hereditary spastic paraplegia, LMN: lower motor neuron, LP: lumbar puncture, MCV: motor nerve conduction velocity, MMN: multifocal motor neuropathy, SCV: sensory nerve conduction velocity, SD: syndrome, SMA: spinal muscular atrophy, UMN: upper motor neuron.