Cortical reflex myoclonus in Rett syndrome

Renzo Guerrini, Paolo Bonanni, Lucio Parmeggiani, Margherita Santucci, Antonia Parmeggiani, Ferdinando Sartucci

Research output: Contribution to journalArticlepeer-review


Rett syndrome (RS) is one of the most frequent causes of mental retardation in females. As there are no known biochemical, genetic, or morphological markers, diagnosis is based on clinical phenotype including severe dementia, autism, truncal ataxia/apraxia, loss of purposeful hand movements, breathing abnormalities, stereotypies, seizures, and extrapyramidal signs. Myoclonus, although reported in some series, has never been characterized. We studied 10 RS patients, age 3 to 20 years, and observed myoclonus in 9. Severity of myoclonus did not correlate with that of the other symptoms or with age. Multifocal, arrhythmic, and asynchronous jerks mainly involved distal limbs. Electromyographic bursts lasted 48 ± 12 msec. Burst-locked electroencephalographic averaging generated a contralateral centroparietal premyoclonus transient preceding the burst by 34 ± 7.2 msec. Motor evoked potentials showed normal latencies, indicating integrity of the corticospinal pathway. Somatosensory evoked potentials were enlarged. The C-reflex was hyperexcitable and markedly prolonged (62 ± 4.3 msec), mainly due to increase in cortical relay time (28.4 ± 4.5 msec). We conclude that RS patients show a distinctive pattern of cortical reflex myoclonus with prolonged intracortical delay of the long-loop reflex.

Original languageEnglish
Pages (from-to)472-479
Number of pages8
JournalAnnals of Neurology
Issue number4
Publication statusPublished - Apr 1998

ASJC Scopus subject areas

  • Neuroscience(all)


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