title: Incomplete inversion of the hippocampus--a common developmental anomaly.
abstract: Incomplete inversion of the hippocampus, an imperfect fetal development, has been described in patients with epilepsy or severe midline malformations. We studied this condition in a nonepileptic population without obvious developmental anomalies. We analyzed the coronal MR images of 50 women and 50 men who did not have epilepsy. Twenty of them were healthy volunteers and 80 were patients without obvious intracranial developmental anomalies, intracranial masses, hydrocephalus or any condition affecting the temporal lobes. If the entire hippocampus (the head could not be evaluated) were affected, the incomplete inversion was classified as total, otherwise as partial. Incomplete inversion of the hippocampus was found in 19/100 subjects (9 women, 10 men). It was unilateral, always on the left side, in 13 subjects (4 women, 9 men): 9 were of the total type, 4 were partial. It was bilateral in six subjects (five women, one man): four subjects had total types bilaterally, two had a combination of total and partial types. The collateral sulcus was vertically oriented in all subjects with a deviating hippocampal shape. We conclude that incomplete inversion of the hippocampus is not an unusual morphologic variety in a nonepileptic population without other obvious intracranial developmental anomalies.
authors.affiliation: Department of Radiology, Uppsala University Hospital, SE 75185 Uppsala, Sweden. dragan.bajic@akademiska.se
authors.forename: Dragan
authors.initials: D
authors.lastname: Bajic
authors.forename: Chen
authors.initials: C
authors.lastname: Wang
authors.forename: Eva
authors.initials: E
authors.lastname: Kumlien
authors.forename: Peter
authors.initials: P
authors.lastname: Mattsson
authors.forename: Staffan
authors.initials: S
authors.lastname: Lundberg
authors.forename: Orvar
authors.initials: O
authors.lastname: Eeg-Olofsson
authors.forename: Raili
authors.initials: R
authors.lastname: Raininko
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D002648:Child; D002675:Child, Preschool; D004833:Epilepsy, Temporal Lobe / Q000473:pathology*; D005260:Female; D006624:Hippocampus / Q000002:abnormalities*; D006801:Humans; D007223:Infant; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged