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Benign segmental myoclonus: electrophysiological evidence of transient dysfunction in the brainstem
1Department of Neurology, Kanazawa University School of Medicine, Kanazawa, Japan. hiroaki@kenroku.kanazawa-u.ac.jp
Abstract:
We present a 66-year-old patient with segmental myoclonus evoked by a brainstem infarction. The myoclonus appeared soon after a cerebrovascular accident and it was evident in the soft palate, jaw, neck, shoulders and upper limbs. Brain MRI showed infarction in the left pons and left cerebellum. Small amounts of orally administered clonazepam were remarkably effective. Electroencephalogram (EEG) and auditory brainstem response (ABR) were normal. Somatosensory evoked potential (SSEP) revealed delays in P 14 and N19 recorded at C3 by right median nerve stimulation. These findings were normalized in 4 days. Seg-mental myoclonus is thought to be evoked by olivary hypertrophy following cerebrovascular accident in the brainstem and is said to be resistant to medication. The limited involvement of the brainstem in our patient may account for the transient segmental myoclonus. The prognosis for this type of segmental myoclonus is excellent.
Insights
A brainstem infarction caused temporary segmental myoclonus in a 66-year-old patient. This condition, often resistant to treatment, resolved quickly with clonazepam, indicating a favorable prognosis.
Area of Science:
- Neurology
- Neuroscience
- Clinical Medicine
Background:
- Segmental myoclonus is a rare movement disorder characterized by involuntary muscle jerks.
- It is often associated with brainstem lesions, particularly cerebrovascular accidents.
- Treatment can be challenging, with many cases proving resistant to medication.
Observation:
- A 66-year-old patient presented with segmental myoclonus affecting the soft palate, jaw, neck, shoulders, and upper limbs.
- Brain MRI revealed infarction in the left pons and left cerebellum.
- Neurological assessments, including EEG and ABR, were normal, while SSEP showed transient delays.
Findings:
- The patient's segmental myoclonus appeared shortly after a cerebrovascular accident.
- Low-dose oral clonazepam was highly effective in managing the myoclonus.
- Somatosensory evoked potential abnormalities normalized within four days.
Implications:
- Limited brainstem involvement may correlate with transient segmental myoclonus.
- This case suggests that segmental myoclonus following brainstem infarction can have an excellent prognosis.
- Early and effective pharmacological intervention, such as with clonazepam, is possible.