Mandibular dysfunction as a reflection of bulbar involvement in SMA type 2 and 3

Area of Science:

• Neurology
• Oral and Maxillofacial Surgery
• Genetics

Background:

• Spinal muscular atrophy (SMA) is a genetic neuromuscular disease affecting motor neurons.
• Bulbar dysfunction is a known complication in SMA, impacting swallowing and speech.
• The effects of SMA on mandibular function are not well-characterized.

Purpose of the Study:

• To evaluate the impact of SMA types 2 and 3 on masticatory performance, mandibular range of motion, and bite force.
• To identify predictors of mandibular dysfunction in patients with SMA.

Main Methods:

• Cross-sectional study comparing 60 patients with SMA types 2 and 3 to 60 age-matched controls.
• Assessment included questionnaires on mandibular function, clinical examination of range of motion (mouth opening, lateral, protrusion), bite force measurement, and masticatory performance evaluation.

Main Results:

• Patients with SMA types 2 and 3 demonstrated significantly reduced mandibular movements (p < 0.001) compared to controls.
• Maximal bite force was 19% lower in SMA patients, with greater reduction in type 2 than type 3.
• SMA type was the strongest predictor for reduced range of motion (R(2) = 0.82), and neck muscle weakness for reduced bite force (R(2) = 0.47).

Conclusions:

• Reduced mandibular mobility and bite force are prevalent complications in SMA.
• SMA type and neck muscle strength are significant correlates of mandibular dysfunction.
• Findings support clinically relevant bulbar involvement in SMA patients.