Value of ultrasound-detected fasciculations for the early diagnosis of motor neuron disease in patients with single-segment, pure lower motor neuron involvement.

OBJECTIVE: To evaluate the early diagnostic value of muscle ultrasound (US)-detected fasciculations in motor neuron disease (MND) patients presenting with single‑region, pure lower motor neuron (LMN) involvement. METHODS: Prospective cohort study enrolling 60 patients with clinical LMN signs confined to one body region. All underwent standardized needle EMG and muscle US at baseline. Final diagnosis determined by follow-up. Agreement between EMG and US, and net diagnostic gain of US were analyzed. RESULTS: 54 MND patients (median disease duration 9 months) were analyzed. US detection rates: bulbar 38.9%-46.3%; high-grade cervical fasciculations 20.4%-37.0%. EMG-US agreement was poor to fair (kappa 0.106-0.360). US provided additional LMN evidence in EMG-negative regions in 27.8% (bulbar), 22.2% (cervical) and 9.3% (lumbosacral). Using US (≥ 2 regions with fasciculations/high-grade) as an ancillary criterion, 53.7% were diagnosed at first visit; median time to diagnosis was 5 months (range 3-8) in those otherwise missed. CONCLUSIONS: Muscle ultrasound is a sensitive, non-invasive complement to EMG, significantly improving early diagnosis in single-region pure LMN presentations. However, specificity estimates remain preliminary due to the limited number of non-MND controls.