Prodromal symptoms in amyotrophic lateral sclerosis from the perspective of the patient and of the caregiver

Objective: Clinically manifest ALS is preceded by a prodromal phase in gene mutation carriers, characterized by mild motor impairment. A well-defined prodromal phase could enable earlier diagnosis and treatment. We investigated the presence of a prodromal phase in sporadic ALS, from the perspective of patients and caregivers. Methods: A survey was conducted of symptom onset in 279 ALS patients from a population-based registry and 150 caregivers. 244 patients and 123 caregivers were included in the primary qualitative analysis, followed by quantitative analysis of identified themes. A prodromal phase was defined as symptoms, in response to open-ended questions, before onset of recorded weakness, bulbar complaints or shortness of breath. Mild motor symptoms were defined as fasciculations, cramps, stiffness, atrophy, reduced sports performance, or mobility issues. Results: 26.6% of patients and 17.5% of caregivers reported a prodromal phase, primarily with mild motor symptoms (patients 23.0%; caregivers 11.4%). Prodromal symptoms occurred a median of 6.0 months (IQR 2.8–11.8 months) before recorded disease onset. In closed-ended questions, 19.2% of patients and 22.2% of caregivers reported cognitive or behavioral symptoms before weakness onset, compared to only 0.6% and 1.8% in open-ended questions. Conclusions: In sporadic ALS, approximately a quarter of patients report a prodromal phase characterized primarily by mild motor symptoms. However, mild motor symptoms alone are unlikely to contribute to earlier disease recognition. Cognitive or behavioral symptoms are often not recognized as part of the clinical spectrum. These findings emphasize the need for reliable biomarkers to detect ALS pathology at an early stage.