Progressive Upper Motor Neuron Predominant Syndrome Initially Suspected as Amyotrophic Lateral Sclerosis: Diagnostic Reassessment Following Extensive Electrophysiological Evaluation

Amyotrophic lateral sclerosis (ALS) remains a clinically challenging diagnosis, particularly during early disease stages or in patients with predominant upper motor neuron (UMN) features without convincing lower motor neuron (LMN) involvement. Electrophysiological reassessment plays a critical role in avoiding premature or inaccurate diagnostic labeling. We report a 51-year-old male with a progressive three-year history of lower limb stiffness, gait dysfunction, imbalance, and hyperreflexia who had previously been suspected to have ALS following outside electrophysiological testing reportedly demonstrating fasciculations within limited upper limb sampling. The patient presented to our center for reassessment because of persistent diagnostic uncertainty and concern regarding the implications of an ALS diagnosis. Repeat comprehensive neurophysiological evaluation at our center included bilateral upper and lower limb nerve conduction studies, F-wave studies, and extensive needle electromyography with additional bulbar muscle sampling. No convincing active denervation, chronic neurogenic remodeling, diffuse LMN degeneration, or bulbar involvement was identified. MRI brain and cervical spine imaging were unremarkable without structural or corticospinal tract pathology. Based on longitudinal clinical evolution, progressive UMN-predominant findings, preserved sensory examination, and absence of convincing electrophysiological LMN involvement despite symptom progression over several years, the overall clinical picture was considered more consistent with a primary lateral sclerosis (PLS)-spectrum disorder rather than classical ALS. This case highlights the importance of repeat multi-regional electrophysiological reassessment, cautious interpretation of isolated fasciculations, and careful longitudinal evaluation in patients with suspected motor neuron disease.