Neurosurgery notes/Anatomy/Cortex/Temporal lobe/Mesial temporal lobe/Uncus (hook)

Uncus (hook)

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Mesial temporal lobe

Relations

  • Anterior
    • Continues with anterior portion of parahippocampal gyrus
  • Inferior
    • Uncal notch
      • Separates parahippocampal gyrus from uncus
  • Superiorly
    • Uncus is continuous with the globus pallidus
    • Posterior-superiorly
      • Inferior choroidal point:
        • Where the choroid plexus of the temporal horn begins;
        • Where the choroidal fissure begins
        • Where the anterior choroidal artery enters the temporal horn through the choroidal fissure
        • Where the hippocampal body meets the hippocampal head.
          • The body has a anterior to posterior orientation
          • The head has a medial to lateral orientation
  • Laterally
    • Rhinal sulcus
      • Separates uncus from temporal pole
  • Medial
    • Crural and ambient cisterns
      • Can herniate through tentorial edge
    • The CN3 passes just below the apex of the uncus

Composed of 5 small gyri

notion image
  • Anterior segment
      • Semilunar gyri (4)
        • Is incontinuation with the globus pallidus (6) superior laterally
        • Lateral and anterior to the semilunar gyrus (12) and globus pallidus (6) is the limen insulae (14)
       
      notion image
    • Ambient gyri (5)
  • Posterior segment
    • Uncinate gyrus, (9)
      • Contains CA1 field of the hippocampal formation
    • Band of Giacomini (10)
      • AKA: Tail of dentate gyrus
      • Contains CA1 field of the hippocampal formation
      • Does not have the denticulations that are the main features of the detate gyrus
      • The dentate gyrus loses its denticulations as it emerges from the fimbrodentate sulcus and enters the roof of the uncal notch.
    • Intralimbic gyrus (11)
      • contains the sectors CA3 and CA4 of the hippocampal formation
      • forms the posterior boundary of the uncus and is the site of attachment to the fimbria.

Medial view

  • Anterior segment:
    • Contains
      • Amygdala
    • Artery
      • M1 and carotid
    • Anteromedial surface
      • Occupied by 2 small gyri
        • Semilunar gyrus
        • Ambient gyrus
          •  
  • Posterior segment:
    • Contains head of hippocampus
    • Artery
      • P2A
    • Posteromedial surface
      • Occupied by 3 small gyri: from anterior to posterior are
        • Uncinate gyrus
        • Band of Giacomini
        • Intralimbic gyrus
    • Inferior surface,
      • Forms the upper wall of the uncal notch
Images
  1. Fasciolar gyrus
  1. Fornix
  1. Dentate gyrus
  1. Choroidal fissure (between the fornix and the thalamus)
  1. Fimbrodentate sulcus
  1. Hippocampal sulcus
  1. Uncus
  1. Uncal notch
  1. Parahippocampal gyrus
  1. Fusiform gyrus
  1. Planum polare
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  1. Rectus gyrus
  1. Olfactory tract
  1. Anterior perforated substance
  1. Semilunar gyrus
  1. Ambient gyrus
  1. Fimbria
  1. Dentate gyrus
  1. Semiannularis sulcus
  1. Uncinate gyrus
  1. Band of Giacomini
  1. Intralimbic gyrus
  1. Uncal notch
  1. Rhinal sulcus
  1. Collateral sulcus
* Entorhinal area
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  1. Globus pallidus
  1. Anteromedial surface of the uncus
  1. Posteromedial surface of the uncus
  1. Uncal notch
  1. Parahippocampal gyrus
  1. Apex of the uncus
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Inferior view

Basal view of the brain
  1. Olfactory tract
  1. Rhinal sulcus
  1. Optic nerve
  1. Anterior segment of the uncus
  1. Tentorial groove
  1. Apex of the uncus
  1. Anterior hippocampal sulcus
  1. Posterior segment of the uncus
  1. Crus cerebri
  1. Parahippocampal gyrus
  1. Lateral mesencephalic sulcus
  1. Medial geniculate body
  1. Collateral sulcus
  1. Pulvinar of the thalamus
  1. Splenium of the corpus callosum
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  1. Temporal pole
  1. Anterior perforated substance
  1. Anterior segment of the uncus
  1. Rhinal sulcus
  1. Apex of the uncus
  1. Posterior segment of the uncus and uncal notch
  1. Parahippocampal gyrus
  1. Fornix
  1. Dentate and fasciolar gyri
  1. Splenium of the corpus callosum
  1. Fusiform gyrus
  1. Collateral sulcus
  1. Isthmus of the cingulate gyrus
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  1. Rhinal sulcus
  1. Anterior perforated substance
  1. Tentorial groove
  1. Uncinate gyrus
  1. Band of Giacomini
  1. Posterior perforated substance
  1. Crus cerebri
  1. Intralimbic gyrus
  1. Fimbria
  1. Substantia nigra
  1. Lateral geniculate body
  1. Fimbro dentate sulcus
  1. Medial geniculate body
  1. Dentate gyrus
  1. Tegmentum
  1. Pulvinar of the thalamus
  1. Choroidal fissure
  1. Splenium of the corpus callosum
  1. Fusiform gyrus
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  1. Genu of the corpus callosum
  1. Head of the caudate nucleus
  1. Lentiform nucleus
  1. Anterior commissure
  1. Uncal recess
  1. Thalamus
  1. Head of the hippocampus
  1. Body of the hippocampus
  1. Collateral eminence
  1. Fimbria
  1. Tail of the hippocampus
  1. Collateral trigone
  1. Bulb of the callosum
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Coronal view

Images

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  • CS: Collateral sulcus
  • B basal vein
  • AC: anterior choroidal artery
      •  
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  • Midbrain
    • divided into two halves, by a sagittal plane
      • Right cerebral peduncles
      • Left cerebral peduncles
    • Cerebral peduncle is demarcated by the substantia nigra
      • Anterior crus cerebri
      • Posterior tegmental
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  • This is an important view as it shows the amygdala is right inferior to the globus pallidus. When doing a amydalahippocampectomy to differentiate between the amygdala and the globus pallidus look at the optic tract.
  1. Superior limiting or superior circular sulcus of the insula
  1. Internal capsule
  1. Thalamus
  1. Insula
  1. Extreme capsule, claustrum, and external capsule
  1. Globus pallidus (with its medial and lateral parts)
  1. Inferior circular or inferior limiting sulcus of the insula
  1. Amygdala
  1. Apex of the uncus
  1. Temporal horn and collateral eminence
  1. Head of the hippocampus
  1. Anterior segment of the uncus
  1. Optic nerve
  1. Limen insulae
* Temporal stem
Coronal cut at the level of the optic chiasm on the left side of the specimen. Coronal cut at the level of the foramen of Monro and the apex of the uncus on the right side of the specimen
Coronal cut at the level of the optic chiasm on the left side of the specimen.
Coronal cut at the level of the foramen of Monro and the apex of the uncus on the right side of the specimen
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  1. Body of the corpus callosum
  1. Body of the caudate nucleus
  1. Septum pellucidum
  1. Thalamus
  1. Columns of the fornix & foramina of Monro
  1. Internal capsule
  1. Lentiform nucleus
  1. Anterior commissure
  1. Lamina terminalis
  1. Limen insulae
  1. Optic nerve
  1. Olfactory tract
Coronal cut has been performed at the level of the optic chiasm
Coronal cut has been performed at the level of the optic chiasm
 

Clinical

  • Area of the hippocampus most vulnerable to hypoxia
    • CA1, also called Sommer’s sector.
    • CA3 area is relatively resistant to hypoxia
  • Hippocampal sclerosis:
    • Neuronal loss mainly occurs in the CA1 region
    • Less neuronal loss: CA4, CA3, and CA2 regions and the dentate gyrus
    • CA2 and dentate gyrus mostly spared