Selective muscle involvement quantification in late-onset Tay Sachs and Sandhoff disease using neuromuscular ultrasound imaging.

OBJECTIVE

Despite functional mobility losses being the primary complaint in late-onset Tay-Sachs and Sandhoff disease (LOTS-SD), a quantitative understanding of neuromuscular degeneration is lacking. Our aim is to quantitatively characterize muscle degeneration using ultrasound measures of muscle thickness, echogenicity, and stiffness. Additionally, we investigate if elbow and knee extensors are preferentially affected in LOTS-SD.

METHODS

Twenty patients diagnosed with LOTS-SD and 20 matched controls (age, sex, BMI) participated. Muscle thickness, echogenicity, and stiffness were quantified and compared across cohorts in the triceps, biceps, rectus femoris (RF) and semimembranosus (SM). For each measurement, the extensor-to-flexor and lower-to-upper-limb muscle ratios (triceps-to-biceps, RF-to-SM, and RF-to-triceps) were also compared.

RESULTS

Patients with LOTS-SD demonstrated triceps, RF, and SM atrophy (24-47%), increased RF and triceps echogenicity (21-36%), and increased RF stiffness (10%). The triceps-to-biceps and RF-to-SM thickness ratios were decreased (-42%, -25%) and increased for echogenicity (32%, 35%). Notably, for the RF-to-triceps ratio, only the stiffness ratio was elevated (18%) in patients.

CONCLUSION

Neuromuscular ultrasound confirmed patterns of preferential elbow/knee extensors degeneration in LOTS-SD. While lower (RF) and upper limb (triceps) atrophy appeared proportionate, elevated RF stiffness indicates potentially varied degeneration pathways for these two muscles.

SIGNIFICANCE: These findings highlight neuromuscular ultrasound's potential role in disease monitoring and differential diagnosis.