Basilar Artery Dissection in Myotonic Dystrophy Type 1

Dear Editor, Myotonic dystrophy type 1 (DM1) is caused by a genetic malfunction involving the overexpression of the CTG sequence in DMPK. This affects the skeletal, cardiac, and smooth muscles, presenting with abnormalities in several body areas. In particular, cardiac fibrosis caused by invasion into cardiac muscle is associated with a high incidence of atrial fibrillation in patients with DM1.1 Atrial fibrillation has been reported as a major causal factor of stroke in DM1.2 Although previous studies have shown that DM1 is associated with an abnormality of the vascular smooth muscle,3 there has been no report of DM1 being related to a compromise of the macrovascular system, which includes arterial dissection. Dissection of the basilar artery (BA) is a very rare disease with an annual incidence of 1/400,000. We report the case of a patient with DM1 who was diagnosed with an acute cerebral infarction due to BA dissection without trauma. Artery dissection could be another etiology of ischemic stroke in patients with myotonic dystrophy. A 58-year-old female visited our clinic due to a gait disturbance, which had worsened 7 days before her visit. She was diagnosed with myotonic dystrophy in her 20s. Her older sister had also been diagnosed with DM1 in her 20s. A neurological examination revealed sensory deficits following light touches in the left facial region and the upper and lower extremities. Moreover, a cerebellar function test revealed left-limb dysmetria and a left-sided falling tendency during gait (National Institutes of Health Stroke Scale score of 5 and modified Rankin Scale score of 3). Percussion myotonia was observed in the abductor pollicis brevis. The findings of routine laboratory tests including of thyroid function were normal. PCRSouthern analysis with a biotin-(CTG) 10 probe revealed that DMPK (CTG) was amplified with over 550 repeats. The characteristic myotonic discharge was observed in the overall muscles. Electrocardiography revealed atrial fibrillation, but no conduction defect or tachycardia was present. Acute infarction of the right pons was confirmed in brain diffusion-weighted magnetic resonance angiography (MRA) (Fig. 1A). Dissection was suspected in the middle portion of the BA (Fig. 1B, C). Transfemoral cerebral angiography was performed to confirm dissection, which revealed flame-like tapering with long-segment stenosis at the same site (Fig. 1D). She was administered 5 mg of apixaban twice daily and 40 mg of atorvastatin once daily, and was discharged after her limb ataxia and gait disturbance improved. DM1 continuously weakens and depletes the muscles in the face, neck, and extremities, and it is characterized by myotonia when the invaded muscle is percussed.4 The severity of DM1 may vary in an individual patient. The adult-onset type is the most common, and its symptoms become distinct from the age of 40 years. DM1 is caused by mutations in DMPK located on chromosome 19q13.3. DM1 presents with abnormalities in several areas of the body, including the musculoskeletal, nervous, circulatory, and endocrine systems, and the gastrointestinal (GI) tract. DM1 presents with mainly musculoskeletal clinical symptoms. However, it also often presents with symptoms associated with the smooth muscle, including vomiting, constipation, diarrhea, and dysphagia resulting from the invasion of the smooth muscle of the GI tract, which can inChan-Hyuk Lee* Seung-Ho Jeon* Byoung-Soo Shin Hyun Goo Kang