Somatosensory Evoked Potentials and Central Motor Conduction Times in children with dystonia and their correlation with outcomes from Deep Brain Stimulation of the Globus pallidus internus

Verity M Mcclelland,Doreen Fialho,Denise Flexney-Briscoe,Graham E Holder,Markus C Elze,Hortensia Gimeno,Ata Siddiqui,Kerry Mills,Richard Selway,Jean-Pierre Lin

doi:10.1016/j.clinph.2017.11.017

Abstract

ObjectivesTo report Somatosensory Evoked Potentials (SEPs) and Central Motor Conduction Times (CMCT) in children with dystonia and to test the hypothesis that these parameters predict outcome from Deep Brain Stimulation (DBS). Methods180 children with dystonia underwent assessment for Globus pallidus internus (GPi) DBS, mean age 10 years (range 2.5–19). CMCT to each limb was calculated using Transcranial Magnetic Stimulation. Median and posterior tibial nerve SEPs were recorded over contralateral and midline centro-parietal scalp. Structural abnormalities were assessed with cranial MRI. One-year outcome from DBS was assessed as percentage improvement in Burke-Fahn-Marsden Dystonia Rating Scale (BFMDRS-m). ResultsAbnormal CMCTs and SEPs were found in 19% and 47% of children respectively and were observed more frequently in secondary than primary dystonia. Of children proceeding to DBS, better outcome was seen in those with normal (n = 78/89) versus abnormal CMCT (n = 11/89) (p = 0.002) and those with normal (n = 35/51) versus abnormal SEPs (n = 16/51) (p = 0.001). These relationships were independent of dystonia aetiology and cranial MRI findings. ConclusionsCMCTs and SEPs provide objective evidence of motor and sensory pathway dysfunction in children with dystonia and relate to DBS outcome. SignificanceCMCTs and SEPs can contribute to patient selection and counselling of families about potential benefit from neuromodulation for dystonia.

Highlights

The benefits of Deep Brain Stimulation (DBS) of the Globus Pallidus internus (GPi) for isolated idiopathic or genetic dystonia are well recognised in both adults and children, with improvements of 52-88% being seen in the Burke-Fahn-Marsden Dystonia Rating Scale motor score (BFMDRS-m)(Coubes et al, 2004, Vidailhet et al, 2005, Zorzi et al, 2005, Alterman et al, 2007)
This study reports Central Motor Conduction Times (CMCT) and SEP data from a cohort of 180 children with dystonia and, for those proceeding to DBS, tests the hypothesis that these neurophysiological markers are associated with outcome
Abnormal CMCTs were seen in a higher proportion of children with acquired (22%) than idiopathic/genetic dystonia (9%)

Summary

Introduction

The benefits of Deep Brain Stimulation (DBS) of the Globus Pallidus internus (GPi) for isolated idiopathic or genetic (formerly termed primary) dystonia are well recognised in both adults and children, with improvements of 52-88% being seen in the Burke-Fahn-Marsden Dystonia Rating Scale motor score (BFMDRS-m)(Coubes et al , 2004, Vidailhet et al , 2005, Zorzi et al , 2005, Alterman et al , 2007). There are growing reports of children with acquired dystonia, such as dyskinetic cerebral palsy (CP) arising from perinatal brain injury, benefitting from DBS (Coubes et al , 2004, Eltahawy et al , 2004, Zorzi et al , 2005, Alterman et al , 2007, Katsakiori et al , 2009, Vidailhet et al , 2009, Air et al , 2011, Marks et al , 2011, Gimeno et al , 2013a, Koy et al , 2013, Lumsden et al , 2013b, Marks et al , 2013, Olaya et al , 2013, Romito et al , 2015). These children respond more modestly, with mean improvement in BFMDRS usually less than 25% (Coubes et al , 2004, Eltahawy et al , 2004, Zorzi et al , 2005, Alterman et al , 2007, Katsakiori et al , 2009, Vidailhet et al , 2009, Marks et al , 2011, Gimeno et al , 2013a, Koy et al , 2013, Lumsden et al , 2013b, Marks et al , 2013), but the benefits gained can significantly enhance the families’ daily lives through improved comfort and daily care

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