Fact-sheet: Incomplete hippocampal inversion


Updated on 03/28/2024 at 10:11 AM

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Definition

Incomplete hippocampal inversion (or incomplete hippocampal malrotation) and incomplete hippocampal formation are normal variants resulting from an embryological arrest of hippocampal inversion

Clinical features

Incidental finding, asymptomatic patient

MRI

Laterality:

  • Most often present on the left.
  • If present on the right, often associated with incomplete inversion on the left.
  • Involvement of the entire hippocampus is very rare and almost exclusively encountered on the right side.

Several forms:

  • Vertical orientation of the collateral sulcus
  • Abnormally rounded or pyramidal shape of the hippocampus
  • Possible inferior displacement of the fornix

Differential diagnosis

Complete forms of hippocampal malrotation or hippocampal malformation: loss of visualization of the internal structure of the hippocampus. To be considered epileptogenic lesions.

Mesial temporal sclerosis