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A 26-year-old woman (patient 1 on the family tree—figure 1) gave a 6-year history of dysarthria, occasional jerks and progressive gait unsteadiness with frequent falls, and had become bedridden. On examination, she had dorsal kyphosis and pes cavus. There was severe truncal and appendicular ataxia, generalised action myoclonus, hyporeflexia, hypotonia and bilateral extensor plantar reflexes. Electromyography with nerve conduction studies identified a sensorimotor polyneuropathy, with intermediate conduction velocities.
Her medical history was unremarkable, with a normal development. She had experienced one recent generalised tonic–clonic seizure. She had an older sister (patient 2 on the family tree—figure 1) with a rapidly progressive nephrotic syndrome starting at the age of 17, becoming steroid resistant and needing haemodialysis after a few months. She also had a normal development and unremarkable medical history. At age of 21, she had developed action myoclonus of the lower limbs, with subjective loss of strength and frequent falls, later progressing to the upper limbs. She started having generalised tonicclonic seizures and lost walking ability in the next year. At aged 28 years, she underwent renal transplantation and died 5 years later due to graft-related complications. Their parents were consanguineous (they were half-siblings) and they had a healthy sister.
How can you localise her myoclonus and what should be the initial steps in the evaluation?
Clinical assessment of pathological myoclonus requires a systematic approach. On neurological examination, it is important to note if the myoclonus appears at rest, on posture or during action. If present at rest, a spinal or brainstem source is more likely, whereas, if action induced, a cortical source should be suspected. Distribution is also important: cortical myoclonus is typically focal or multifocal, spinal segmental myoclonus can also be focal (but usually is stimulus …
Contributors MP: Study concept and design, acquisition of data, analysis and interpretation, drafting/revising the manuscript for content. JD: revising the manuscript for content. MdCM: acquisition of data, analysis and interpretation of data, revising the manuscript for content.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Competing interests None declared.
Patient consent for publication Parental/guardian consent obtained.
Provenance and peer review Not commissioned. Externally peer reviewed by Henry Houlden, London, UK, and Richard Appleton, Liverpool, UK.
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