title: The value of repeat neuroimaging for epilepsy at a tertiary referral centre: 16 years of experience.
abstract: OBJECTIVE
  Magnetic resonance imaging (MRI) is the investigation of choice for detecting structural lesions that underlie and may accompany epilepsy. Despite advances in imaging technology, 20-30% of patients with refractory focal epilepsy have normal MRI scans. We evaluated the role of repeated imaging with improved MRI technology - an increase in field strength from 1.5T to 3T and superior head coils - in detecting pathology not previously seen.
  
  
  METHODS
  Retrospective review of a large cohort of patients attending a tertiary epilepsy referral centre who underwent MRI at 1.5T (1995-2004) and subsequently 3T (2004-2011) with improved head coils. Scan reports were reviewed for the diagnoses and medical notes for the epilepsy classification.
  
  
  RESULTS
  804 patients underwent imaging on both scanners, the majority with focal epilepsy (87%). On repeat scanning at 3T, 37% of scans were normal and 20% showed incidental findings. Positive findings included hippocampal sclerosis (13%), malformations of cortical development (8%), other abnormalities (4%) and previous surgery (18%). A total of 37 (5%) relevant new diagnoses were made on the 3T scans not previously seen at 1.5T. The most common new findings were hippocampal sclerosis, focal cortical dysplasia and dysembryoplastic neuroepithelial tumour. These findings affected patient management with several patients undergoing neurosurgery.
  
  
  CONCLUSIONS
  The higher field strength and improved head coils were associated with a clinically relevant increased diagnostic yield from MRI. This highlights the importance of technological advances and suggests that rescanning patients with focal epilepsy and previously negative scans is clinically beneficial.
authors.affiliation: Epilepsy Society MRI Unit, Department of Clinical and Experimental Epilepsy, UCL Institute of Neurology, London, United Kingdom. g.winston@ucl.ac.uk
authors.forename: Gavin P
authors.initials: GP
authors.lastname: Winston
authors.forename: Caroline
authors.initials: C
authors.lastname: Micallef
authors.forename: Brian E
authors.initials: BE
authors.lastname: Kendell
authors.forename: Philippa A
authors.initials: PA
authors.lastname: Bartlett
authors.forename: Elaine J
authors.initials: EJ
authors.lastname: Williams
authors.forename: Jane L
authors.initials: JL
authors.lastname: Burdett
authors.forename: John S
authors.initials: JS
authors.lastname: Duncan
mesh_terms: D000328:Adult; D001921:Brain / Q000473:pathology*; D015331:Cohort Studies; D004569:Electroencephalography; D004827:Epilepsy / Q000145:classification / Q000175:diagnosis* / Q000453:epidemiology; D005260:Female; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008279:Magnetic Resonance Imaging; D008297:Male; D012017:Referral and Consultation; D012189:Retrospective Studies; D015899:Tomography, Emission-Computed, Single-Photon
keywords: Epilepsy surgery; Focal cortical dysplasia; Refractory epilepsy; Structural MRI
references.citation: Clin Radiol. 2011 Mar;66(3):278-86
references.pmid: 21295209
references.citation: Brain. 2002 Aug;125(Pt 8):1719-32
references.pmid: 12135964
references.citation: Epilepsia. 1998 Dec;39(12):1375-6
references.pmid: 9860078
references.citation: Epilepsia. 1997 Nov;38(11):1255-6
references.pmid: 9579930
references.citation: Neurology. 2003 Jan 28;60(2):191-5
references.pmid: 12552029
references.citation: Arch Neurol. 1993 Jan;50(1):65-9
references.pmid: 8418802
references.citation: Epileptic Disord. 2005 Sep;7 Suppl 1:S10-3
references.pmid: 16120488
references.citation: Epilepsia. 2008 May;49(5):786-93
references.pmid: 18076641
references.citation: AJNR Am J Neuroradiol. 1995 Feb;16(2):339-43
references.pmid: 7726083
references.citation: Med Image Comput Comput Assist Interv. 2008;11(Pt 1):645-52
references.pmid: 18979801
references.citation: J Neurol Neurosurg Psychiatry. 2002 Dec;73(6):643-7
references.pmid: 12438463
references.citation: Neurology. 2005 Oct 11;65(7):1026-31
references.pmid: 16217054
references.citation: Epilepsia. 2004 Aug;45(8):954-9
references.pmid: 15270762
references.citation: Arch Neurol. 1998 Mar;55(3):346-8
references.pmid: 9520008
references.citation: Nat Rev Neurol. 2010 Oct;6(10):537-50
references.pmid: 20842185
references.citation: J Neurol Neurosurg Psychiatry. 1996 Nov;61(5):433-43
references.pmid: 8965090
references.citation: J Neurol Neurosurg Psychiatry. 1995 Apr;58(4):439-43
references.pmid: 7738550
references.citation: Magn Reson Imaging Clin N Am. 1998 Feb;6(1):139-54
references.pmid: 9449745
references.citation: J Neurol Neurosurg Psychiatry. 1998 Nov;65(5):656-64
references.pmid: 9810933
references.citation: J Magn Reson Imaging. 2009 Aug;30(2):256-62
references.pmid: 19629993
references.citation: Epilepsia. 2000 Jul;41(7):843-9
references.pmid: 10897155
references.citation: Semin Ultrasound CT MR. 2007 Dec;28(6):451-61
references.pmid: 18075001
references.citation: PLoS One. 2011 Feb 04;6(2):e16430
references.pmid: 21326599