Measuring Myotonia: Normative Values and Comparison with Myotonic Dystrophy Type 1

Area of Science:

• Neurology
• Clinical Neuroscience
• Rehabilitation Medicine

Background:

• Myotonia, a rare neuromuscular disorder, is characterized by delayed muscle relaxation.
• Establishing population-specific normative data is crucial for accurate clinical assessment.
• Myotonic Dystrophy Type 1 (DM1) is a primary genetic cause of myotonia.

Purpose of the Study:

• To determine normative values for myotonia-related clinical tests in the Hungarian population.
• To compare these normative values with those of patients diagnosed with myotonic dystrophy type 1 (DM1).
• To evaluate the influence of age and sex on muscle relaxation and strength in healthy individuals.

Main Methods:

• Conducted relaxation tests (eye, tongue, palm openings), handgrip strength, and nine-hole peg test.
• Recruited 139 healthy Hungarian individuals and 31 patients with DM1.
• Analyzed data for age and sex-related differences in controls and compared controls to DM1 patients.

Main Results:

• No significant age-related decline observed in handgrip strength or relaxation tests (p < 0.05).
• Significant differences (p < 0.05) were found in all tested parameters between healthy controls and DM1 patients.
• Healthy males exhibited stronger handgrip and slower relaxation times compared to females; these sex differences were absent in DM1 patients.

Conclusions:

• Normative values for myotonia relaxation tests across various age groups in the Hungarian population were successfully established.
• The study supports using population averages rather than age-specific groups for relaxation test evaluations in myotonia.
• These findings provide valuable reference data for the clinical evaluation and diagnosis of myotonia, particularly DM1.