[Thomsen myotonia congenita and strabismus: recording saccades in myotonic diseases].J Fr Ophtalmol. 2006 Mar; 29(3):271-80.JF
Thomsen myotonia is an autosomal dominant, but not dystrophic myotonia. We report a family case associating congenital Thomsen's myotonia, strabismus, and ocular myopathy. We successively studied seven isolated patients presenting a myotonic disease and two controls and recorded the ocular saccades of these patients (amplitude, velocity) as a comparison for our family case.
PATIENTS AND METHODS
Four women from the same family presented Thomsen myotonia associated with strabismus. In addition to the clinical manifestations, the electro-oculographic analysis showed saccade alterations. The saccades of the seven other isolated patients, recruited in a neurology department, were evaluated by electro-oculographic recordings according to four different paradigms.
The patients within our family case all presented esotropia, with or without a vertical oculomotor disorder. Clinical examination reported alterations in ocular motility--impairment and slowness of ocular movements--suggesting a myopathic disorder. The electro-oculographic recordings reported a slowing of saccades with increasing duration. For the isolated cases, the slowing of saccades observed was only reported for the patients with myotonic dystrophy (Steinert disease); nevertheless, we failed to show any myotonic phenomena.
No cases associating Thomsen myotonia, strabismus, and electro-oculographic disorders have been reported in the literature to date. The electro-oculographic slowing of saccades is not rare in myotonic dystrophy (Steinert disease), but in Thomsen myotonia this has never been reported.
This is the first report concerning Thomsen myotonia associated with strabismus and alterations of saccades. The mechanism of this disorder has yet to be discovered, as for Steinert disease.