A 62-year-old woman developed spontaneous involuntary rhythmic counterclockwise rotatory movement of the right scapula with a frequency of 2.5–3 Hz [Video 1], which was also present during sleep, without significant medical history. Neurologic examination revealed right scapular movement, absent deep tendon reflexes in both upper limbs, and impaired pain and temperature sensations in C4–C8 dermatome on the right side. Surface electromyography revealed burst of 0.2–0.4 s with interburst interval of 0.4–0.6 s occurring at the rate of 2.5–3 Hz in C2–C6 innervated right periscapular muscles, including rhomboids, trapezius, levator scapulae, and serratus anterior. Electroencephalography (EEG) was normal and back-averaging did not show cortical correlates. Magnetic resonance imaging of the cervical spine suggested syringomyelia extending from cervicomedullary junction to C6 vertebra level [Figure 1]. The postulated mechanism in spinal segmental myoclonus in syringomyelia is due to hyperexcitability of alpha motoneurons resulting from damage of inhibitory interneurons located in the spinal cord gray matter.[1,2]
Figure 1.
(a and b) T1- and T2-weighted Sagittal sequence magnetic resonance imaging of cervical spine showing syringomyelia extending from cervicomedullary junction up to C6 vertebra level (arrow)
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REFERENCES
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