The phenotypic spectrum of DYT24 due to ANO3 mutations.
Bottom Line: Electrophysiology in two patients with two different mutations showed co-contraction of antagonist muscles, confirming dystonia, and a 6-Hz arm tremor at rest, which increased in amplitude during action.In summary, ANO3 causes a varied phenotype of young-onset or adult-onset craniocervical dystonia with tremor and/or myoclonic jerks.Patients with familial cervical dystonia who also have myoclonus-dystonia as well as patients with prominent tremor and mild dystonia should be tested for ANO3 mutations.
Affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London, United Kingdom; Neurology Clinic, Attiko Hospital, University of Athens, Greece.Show MeSH
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Mentions: His daughter, patient IV-1 (age 39 years), developed laryngeal dysphonia at the age of 5 years and, shortly thereafter, difficulties with her jaw. At age 14 years, she developed tremor of her head and arms. Alcohol had no influence on the tremor. On examination at age 39 years, she had a torticollis to the left and head tremor. She had occasional finger and arm tremor on arms outstretched and occasional superimposed myoclonic jerks. She had laryngeal dysphonia and mild oromandibular dystonia (Video Segment 2A). Electrophysiology on this patient showed intermittent blepharospasm (Fig. 2) and torticollis to the right. There was underlying, continuous muscle over-activity in the levator scapulae, ECR, and FCR. There was tremor of the neck, trunk, and limbs. There was a mild limb co-contraction tremor with the hand supported in semisupination, against gravity and during action, at about 6 Hz. The myoclonic jerks of the neck were mostly torticollic rather than retrocollic. The duration of myoclonus was about 250 msec with a variable frequency of 3 to 4 Hz at rest. There were no interruptions of muscle activity when holding both arms against gravity. Auditory stimulation (tapping stimulation of the mantle area) did not produce any abnormal startle response. EEG back-averaging was not possible because of the dystonic pattern underlying the muscle bursts, which nonetheless were of long duration (250 msec). An investigation of somatosensory evoked potentials did not indicate any giant evoked potentials (P25-N35, 4 μV; N20-P25, 6.6. μV).
Affiliation: Sobell Department of Motor Neuroscience and Movement Disorders, University College London (UCL) Institute of Neurology, London, United Kingdom; Neurology Clinic, Attiko Hospital, University of Athens, Greece.