Neurosurgery notes/Anatomy/Cortex/Temporal lobe/Mesial temporal lobe/Parahippocampal gyrus

Parahippocampal gyrus

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Mesial temporal lobe

Location

  • Occupies the transitional area between the basal and the mesial surfaces of the temporal lobe.
  • Contiguous with the fusiform gyrus and with the remainder of the basal surface of the brain.

Relations

  • Anteriorly
    • Deviates medially and bends posteriorly to form the uncus.
    • Lateral
      • Rhinal sulcus
        • Marks the lateral limit of the entorhinal area of the parahipocampal gyrus
  • Posteriorly
    • just below the splenium of the corpus callosum, it is often intersected by the anterior calcarine sulcus, which divides the posterior portion of the parahippocampal gyrus into
      • Isthmus of the cingulate gyrus superiorly, which continues as the cingulate gyrus
      • Lingual gyrus, floor of the calcarine sulcus
    • Posteriorly, it continues along the cingulate gyrus.
  • Superiorly
    • Separated from dentate gyrus by hippocampal sulcus
  • Laterally
    • Posterior: collateral sulcus, which bulges superiorly into the lateral part of the floor of the temporal horn as the collateral eminence anteriorly and the collateral trigone posteriorly
      • the location of the collateral sulcus and consequently the location of the lateral part of the floor of the temporal horn can be determined angiographically by following the inferior temporal branches of the posterior cerebral artery as they descend into the depth of the collateral sulcus before continuing on the surface of the fusiform gyrus
  • Medially
    • Runs under the thalamus along the ambient cistern and its contents
    • Contents of ambient cistern
      • Free edge of tentorium
      • CN3
      • PCOM

Components

  • Subiculum
    • Medial round edge of the parahippocampal gyrus
  • Presubiculum
  • Parasubiculum
  • Entorhinal area
    • An important histological concept that plays a major role in neurosurgery, and especially in epilepsy surgery,
    • Located within the anterior 1/3 of the parahippocampal gyrus and the anteroinferior portion of the anterior segment of the uncus;
    • posteriorly, on the parahippocampal gyrus, it extends slightly behind the level of the posterior pole of the uncus.
    • The entorhinal area therefore forms a "shell" around the temporal amygdala
    • It is limited laterally by the rhinal sulcus anteriorly and the collateral sulcus posteriorly.
    • The entorhinal area is composed of the six-layered mesocortex,
    • F(x)
      • A relay for both efferent and afferent connections between the hippocampus and the isocortical association cortex in the temporal parietal, and frontal lobes

Images

notion image
 
  1. Central sulcus
  1. Postcentral gyrus
  1. Postcentral sulcus
  1. Cingulate sulcus
  1. Marginal ramus of the cingulate sulcus
  1. Cingulate gyrus
  1. Corpus callosum
  1. Subparietal sulcus
  1. Precuneus
  1. Parieto-occipital sulcus
  1. Caudate nucleus
  1. Isthmus of the cingulate gyrus
  1. Cuneus
  1. Thalamus
  1. Calcarine sulcus
  1. Fornix
  1. Dentate and fasciolar gyri
  1. Anterior calcarine sulcus
  1. Lingual gyrus
  1. Anterior perforated substance
  1. Uncus
  1. Parahippocampal gyrus
  1. Rhinal sulcus
  1. Collateral sulcus
  1. Fusiform gyrus (occipitotemporal gyrus)
notion image
 
  1. Lateral orbital gyrus
  1. Anterior orbital gyrus
  1. Medial orbital gyrus
  1. Rectus gyrus
  1. Olfactory tract
  1. Optic nerve
  1. Amygdala
  1. Internal carotid artery
  1. Tuber cinereum and pituitary stalk
  1. Parahippocampal gyrus
  1. Rhinal sulcus
  1. Temporal horn cavity
  1. Head of the hippocampus
  1. Posterior perforated substance
  1. Optic tract
  1. Medial geniculate body
  1. Trochlear nerve
  1. Tail of the hippocampus
  1. Pineal gland
  1. Fusiform gyrus (occipitotemporal gyrus)
  1. Collateral sulcus
  1. Occipitotemporal sulcus