[Motor neuron diseases from a radiological perspective : Focus on amyotrophic lateral sclerosis]

Motor neuron diseases (MND) affect the upper and/or lower motor neurons. Radiological diagnostics primarily serve to systematically exclude treatable mimics and support the clinical and electrophysiological diagnosis. The focus is on amyotrophic lateral sclerosis (ALS); supplementary progressive muscular atrophy (PMA, purely lower motor neuron, LMN disease) and spinal muscular atrophy (SMA).

Which imaging signs support the diagnosis of ALS, how do electromyography/magnetic resonance imaging (EMG/MRI) fit into the Gold Coast criteria and which other motor neuron diseases are relevant?

Overview of clinical criteria (Gold Coast), genetics and typical MRI findings of the brain, spinal cord and musculature.

Gold Coast core: progressive motor deterioration, upper motor neuron (UMN) and LMN signs in ≥ 1 region or LMN in ≥ 2 regions and exclusion of alternative causes.

susceptibility-weighted imaging (SWI) motor band sign as UMN marker; T2/fluid-attenuated inversion recovery (FLAIR) hyperintensities along the corticospinal tract with low sensitivity, moderate specificity; T1 bright tongue as an indication of chronic denervation in bulbar involvement. EMG: detection of subclinical LMN involvement, sometimes limited in UMN-dominant/bulbar courses. PMA: Pure purely LMN symptoms, often continuum to ALS. SMA: Autosomal autosomal recessive (SMN1 deletion).

The diagnosis remains primarily clinical; EMG and MRI are supportive. The radiological priority is the exclusion of mimics. The UMN markers increase diagnostic certainty in the context of clinical/EMG findings but do not replace them. Clear findings facilitate classification according to Gold Coast. The PMA and SMA require careful differential diagnostics; characteristic MRI patterns support progression and treatment planning.