Preserved widespread N18 and progressive loss of P13/14 of median nerve SEPs in a patient with unilateral medial medullary syndrome

Electroencephalography and Clinical Neurophysiology
M SonooT Shimizu

Abstract

Median nerve somatosensory evoked potentials (SEPs) in a patient with unilateral medial medullary syndrome of recent onset having an MRI-confirmed lesion at upper medulla were investigated. Cortical N20 following stimulation of the affected limb was extremely depressed and delayed, whereas widespread N18, which was best manifested by the CPi-C2S lead (CPi is centroparietal electrode ipsilateral to the stimulation), showed no significant difference regarding amplitude and duration between affected and non-affected sides. The result supported our previous opinion that the principal part of N18, the broad negativity lasting around 20 ms, originates from the cuneate nucleus at the medullary level. Less steep onset of N18 on the affected side suggested that some structures rostral to the cuneate nucleus, possibly the termination of the overall ascending volley, may contribute to the earliest part of N18. P13/14 on the affected side normally preserved at the first examination progressively declined and finally disappeared after 4 months, which suggested that the major part of P13/14 is generated within caudalmost medial lemniscus, as well as the occurrence of retrograde degeneration of lemniscal fibers.

Citations

Oct 21, 1998·Electroencephalography and Clinical Neurophysiology·G M ManzanoJ A Nóbrega
Jun 3, 2014·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·Theresa GötzJens Haueisen
Jul 21, 1999·Arquivos de neuro-psiquiatria·G M ManzanoJ A Nóbrega
Aug 6, 2000·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·T Yamada
Aug 6, 2000·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·D Restuccia
Aug 6, 2000·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·M Sonoo
Jul 4, 2001·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·M SonooT Shimizu
Aug 6, 2000·Journal of Clinical Neurophysiology : Official Publication of the American Electroencephalographic Society·G CheronS Borenstein
Aug 29, 2021·Clinical Neurophysiology : Official Journal of the International Federation of Clinical Neurophysiology·Angelo InsolaMassimiliano Valeriani

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