Eye movement disorders in myotonic dystrophy type 1.
Ryuichi Osanai1, Masanobu Kinoshita, Kazuhiko Hirose
1Department of Otolaryngology, Kashiwa Kousei General Hospital, 3-8-20 Akebono, Kashiwa, Chiba, Japan. CBA01622@nifty.com
Acta Oto-Laryngologica. Supplementum
|April 12, 2008
Summary
Eye movement abnormalities in myotonic dystrophy type 1 (DM1) are linked to extraocular muscle damage rather than central oculomotor disorders. Saccadic slowing correlates with disease severity, supporting this extraocular muscle hypothesis.
Area of Science:
- Neurology
- Ophthalmology
- Genetics
Background:
- Myotonic dystrophy type 1 (DM1) is a multisystem disorder.
- Eye movement abnormalities are common in DM1 patients.
- The underlying cause of these disorders (central vs. peripheral) is debated.
Purpose of the Study:
- To investigate whether eye movement disorders in DM1 stem from central oculomotor system dysfunction or extraocular muscle damage.
- To correlate oculomotor function with (CTG)n repeat length in DM1.
Main Methods:
- Oculomotor function tests were performed on 29 DM1 patients and 12 controls.
- Correlations between saccadic velocity, nystagmus parameters, and (CTG)n length were analyzed.
Main Results:
- DM1 patients exhibited significantly lower saccadic velocity, maximum slow phase velocity of optokinetic nystagmus (OKNspv), and maximum slow phase velocity of caloric nystagmus (CNspv) compared to controls.
- Visual suppression (VS) of caloric nystagmus was mildly reduced in DM1 patients.
- Higher (CTG)n repeat lengths in DM1 patients correlated with reduced saccadic velocities.
- Maximum frequency of optokinetic nystagmus (OKNfq) did not differ significantly between groups.
Conclusions:
- The findings suggest that eye movement disorders in DM1 are not primarily due to central oculomotor system dysfunction.
- Diminished OKNspv and CNspv, along with saccadic slowing, support the hypothesis of extraocular muscle involvement.
- The results indicate that disease severity, as indicated by (CTG)n length, influences saccadic slowing.
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