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Title: Hippocampal malrotation is an anatomic variant and has no clinical significance in MRI-negative temporal lobe epilepsy
Austin Authors: Tsai, Meng-Han;Vaughan, David N;Perchyonok, Yuliya ;Fitt, Gregory J ;Scheffer, Ingrid E ;Berkovic, Samuel F ;Jackson, Graeme D 
Affiliation: Austin Health, Heidelberg, Victoria, Australia
Department of Medicine, Epilepsy Research Centre, Austin Health, University of Melbourne, Heidelberg, Victoria, Australia
Department of Neurology, Kaohsiung Chang Gung Memorial Hospital, Kaohsiung, Taiwan
Department of Nursing, Meiho University, Pingtung, Taiwan
Department of Neurology, Austin Health, Florey Institute of Neuroscience and Mental Health, Melbourne, Victoria, Australia
Department of Radiology, Austin Hospital, Melbourne, Victoria, Australia
Department of Paediatrics, Royal Children's Hospital, University of Melbourne, Melbourne, Victoria, Australia
Issue Date: 26-Aug-2016
Date: 2016-08-26
Publication information: Epilepsia 2016; online first: 26 August
Abstract: OBJECTIVE: There is considerable difficulty in diagnosing hippocampal malrotation (HIMAL), with different criteria of variable reliability. Here we assess qualitative and quantitative criteria in HIMAL diagnosis and explore the role of HIMAL in magnetic resonance imaging (MRI)-negative temporal lobe epilepsy (TLE). METHODS: We studied the MRI of 155 adult patients with MRI-negative TLE and 103 healthy volunteers, and we asked (1) what are the qualitative and quantitative features that allow a reliable diagnosis of HIMAL, (2) how common is HIMAL in a normal control population, and (3) is HIMAL congruent with the epileptogenic side in MRI-negative TLE. RESULTS: We found that the features that are most correlated with the expert diagnosis of HIMAL are hippocampal shape change with hippocampal diameter ratio > 0.8, lack of normal lateral convex margin, and a deep dominant inferior temporal sulcus (DITS) with DITS height ratio > 0.6. In a blinded analysis, a consensus diagnosis of unilateral or bilateral HIMAL was made in 25 of 103 controls (24.3% of people, 14.6% of hippocampi-14 left, six right, 10 bilateral) that did not differ from 155 lesion-negative TLE patients where 25 had HIMAL (16.1% of patients, 11.6% of hippocampi-12 left, two right, 11 bilateral). Of the 12 with left HIMAL only, 9 had seizures arising from the left temporal lobe, whereas 3 had right-sided seizures. Of the two with right HIMAL only, both had seizures arising from the left temporal lobe. SIGNIFICANCE: HIMAL is an anatomic variant commonly found in controls. HIMAL is also an incidental nonpathologic finding in adult MRI-negative TLE and should not influence surgical decision making.
DOI: 10.1111/epi.13505
ORCID: 0000-0002-2311-2174
Journal: Epilepsia
PubMed URL:
Type: Journal Article
Subjects: Hippocampal sclerosis
Incomplete hippocampal infolding
Lesion-negative epilepsy
Appears in Collections:Journal articles

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