Dental and Craniofacial Findings in Eight Miniature Schnauzer Dogs Affected by Myotonia Congenita: Preliminary Results

Myotonia is a clinical sign characterized by the delay of skeletal muscle relaxation following the cessation of a voluntary activity or the termination of an electrical or mechanical stimulus. Recently, Miniature Schnauzers with myotonia congenita associated with defective chloride ion conductance across the skeletal muscle membrane were identified. Congenital myotonia in these dogs appears to follow an autosomal recessive mode of inheritance. Craniofacial and dental findings of eight Miniature Schnauzer dogs with myotonia congenita are described in the present paper. These findings include: delayed dental eruption of both deciduous and permanent dentition: persistent deciduous dentition; unerupted or partially erupted permanent teeth: crowding and rotation of premolar and or incisor teeth: missing teeth: increased interproximal space between the maxillary fourth premolar and first molar teeth: decreased interproximal space between the maxillary canine and lateral incisor teeth: inability to fully close the mouth due to malocclusion: distoclusion: and, decreased mandibular range of motion. A long narrow skull with a flattened zygomatic arch and greater mandibular body curvature were also consistent findings in the affected dogs. The small number of dogs studied prevents conclusive statements about the origin of these abnormalities, however it is interesting that only 1 of 45 unaffected Miniature Schnauzer dogs showed similar traits.