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.