Neurosurgery notes/Anatomy/White matter tracts/Commissural fibres/Anterior commissure

Anterior commissure

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Commissural fibres

General

  • Situated in the anterior wall of the third ventricle at the upper end of the lamina terminalis
  • Exposed at lateral dissection, after the removal of the IFOF, the UF, the amygdala, the hippocampus, and part of the anterior perforated substance
  • A small bundle that crosses the midline in front of the columns of the fornix
  • Shaped somewhat like the handlebars of a bicycle.

Two crus

  • Anterior crus (anterior projection)
    • Extends forward
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  • Posterior crus (posterior projection)
    • Extends laterally
    • Has 2 extensions
      • Temporal extensions
          • notion image
      • Occipital extensions
          • notion image
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Relationships

  • Lateral expansion of the AC lies above the substantia innominata and inferomedially to the IFOF, covered by a thin layer of white matter called the canal of Gratiolet.
    • This bundle continues posteriorly within the temporal stem
      • Gratiolet's canal: a thin sheet coving the anterior commissure (radiokey)
      Inferomedial view of the right hemisphere. Anterior commissure: 1, anterior limb of the anterior commissure (AC); 2, lateral (temporal) limb of the AC; 3, canal of Gratiolet; 4, corpus of the AC; Fornix: 5, anterior column of the fornix; 6, corpus of the fornix; 7, psalterium of the fornix; 13, posterior column of the fornix; 8, mammillothalamic tract (of Vicq d’Azyr); 9, pes pedunculi; 10, locus niger; Corpus callosum: 11, ventral radiations of the corpus callosum; 12, genu of the corpus callosum; 14, optic chiasma; 15, pulvinar; 16, thalamus; 17, uncinate fasciculus; 18, choroid plexus; 19, head of the caudate nucleus.
      Inferomedial view of the right hemisphere. Anterior commissure: 1, anterior limb of the anterior commissure (AC); 2, lateral (temporal) limb of the AC; 3, canal of Gratiolet; 4, corpus of the AC; Fornix: 5, anterior column of the fornix; 6, corpus of the fornix; 7, psalterium of the fornix; 13, posterior column of the fornix; 8, mammillothalamic tract (of Vicq d’Azyr); 9, pes pedunculi; 10, locus niger; Corpus callosum: 11, ventral radiations of the corpus callosum; 12, genu of the corpus callosum; 14, optic chiasma; 15, pulvinar; 16, thalamus; 17, uncinate fasciculus; 18, choroid plexus; 19, head of the caudate nucleus.
      Inferior view of the left hemisphere. 2, lateral (temporal) limb of the anterior commissure; 3, canal of Gratiolet; 9, pes pedunculi; 15, pulvinar; 18, choroid plexus; 20, optic tract; 21, ansa peduncularis; 22, the Meyer loop; 23, anterior part of optic radiation; 24, uncinate fasciculus; 27, septum pellucidum; 28, mammillary body; 29, posterior perforating substance; 30, atrium of the lateral ventricle; 31, caudatolenticular bridges; 32, ventral callosal radiations of Peltier.
      Inferior view of the left hemisphere. 2, lateral (temporal) limb of the anterior commissure; 3, canal of Gratiolet; 9, pes pedunculi; 15, pulvinar; 18, choroid plexus; 20, optic tract; 21, ansa peduncularis; 22, the Meyer loop; 23, anterior part of optic radiation; 24, uncinate fasciculus; 27, septum pellucidum; 28, mammillary body; 29, posterior perforating substance; 30, atrium of the lateral ventricle; 31, caudatolenticular bridges; 32, ventral callosal radiations of Peltier.
      Medial aspect of the right cerebral hemisphere, showing the rostral division of the stria terminalis: Amn: Amygdaloid nuclear complex, 2: Baso-lateral, 3: Baso-medial, 4: Cortical, CiG: Cingulate gyrus, cnb: Caudate nucleus body, cnh: Caudate nucleus head, cnt: Caudate nucleus tail, DG: Dentate gyrus, faG: Fasciolaris gyrus, Fc: Column of fornix, fc: Fasciola cinerea, Fcr: Crus of the fornix, Fi: Fimbria, gCC: Genu of the corpus callosum, GR: Gyrus rectus, sCG: Subcallosum gyrus, ssplG: Subplenial gyrus, Hy: Hypothalamus, ICa: Internal capsule, iThad: Interthalamic adhesion, Lvac: Lateral ventricle anterior cornu, MB: Mamillary body, mlst: Medial longitudinal stria, pHG: Parahippocampal gyrus, rCC: Rostrum of the corpus callosum, splCC: Splenium of the corpus callosum, ssplG: Subsplenial gyrus, strt: Stria terminalis, a: Ending fasciculus (supra-commissural component) destinated to the paraterminalis gyrus and to the accumbens and septal nuclei, b: Other ending fasciculus (hypothalamic component) destinated to the anterior commissure, the fornix and the hypothalamus), tCC: Truncus of the corpus callosum, Th: Thalamus, Tpo: Temporal pole, Un: a uncal apex, II: Optic nerve. Red arrow: It shows the commissural component of strt entering the Gratiolet’s canal (the anterior commissure has been removed in order to see the fibres of this commissural component). Little black circles: Hypothalamic sulcus. White asterisk: Velum terminale of Aeby. The posterior portion of the diencephalon has been widely removed in order to show very well the stria terminalis. It is the same for the fornix's body. The rostral part of the septum pellucidum is tracted up by a little retractor. A forceps pulls lightly the hypothalamus's floor.
      Medial aspect of the right cerebral hemisphere, showing the rostral division of the stria terminalis: Amn: Amygdaloid nuclear complex, 2: Baso-lateral, 3: Baso-medial, 4: Cortical, CiG: Cingulate gyrus, cnb: Caudate nucleus body, cnh: Caudate nucleus head, cnt: Caudate nucleus tail, DG: Dentate gyrus, faG: Fasciolaris gyrus, Fc: Column of fornix, fc: Fasciola cinerea, Fcr: Crus of the fornix, Fi: Fimbria, gCC: Genu of the corpus callosum, GR: Gyrus rectus, sCG: Subcallosum gyrus, ssplG: Subplenial gyrus, Hy: Hypothalamus, ICa: Internal capsule, iThad: Interthalamic adhesion, Lvac: Lateral ventricle anterior cornu, MB: Mamillary body, mlst: Medial longitudinal stria, pHG: Parahippocampal gyrus, rCC: Rostrum of the corpus callosum, splCC: Splenium of the corpus callosum, ssplG: Subsplenial gyrus, strt: Stria terminalis, a: Ending fasciculus (supra-commissural component) destinated to the paraterminalis gyrus and to the accumbens and septal nuclei, b: Other ending fasciculus (hypothalamic component) destinated to the anterior commissure, the fornix and the hypothalamus), tCC: Truncus of the corpus callosum, Th: Thalamus, Tpo: Temporal pole, Un: a uncal apex, II: Optic nerve. Red arrow: It shows the commissural component of strt entering the Gratiolet’s canal (the anterior commissure has been removed in order to see the fibres of this commissural component). Little black circles: Hypothalamic sulcus. White asterisk: Velum terminale of Aeby. The posterior portion of the diencephalon has been widely removed in order to show very well the stria terminalis. It is the same for the fornix's body. The rostral part of the septum pellucidum is tracted up by a little retractor. A forceps pulls lightly the hypothalamus's floor.
  • Posterior
    • 3rd ventricle
    • fornix
  • Anterior
    • Medially: cingulum ( subcallosal)
    • laterally caudate nuclei
  • Superior
    • Fornix
    • Genu of internal capsule
  • Inferior
    • Lamina terminalis

Connections

  • Connect the olfactory pathway
  • Connect the anterior part of temporal lobes between the 2 cerebral hemispheres.

Function

  • Olfactory function
  • Visual processing memory
  • Can be used to compensate for absent corpus callosum by integrating interhemispheric visual information

Deficit

  • Split brain patients with anterior commissurotomy: anomia for olfactory stimuli presented to the right nostril
  • Memory deficits

Images

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AC is shown superficial to it is the columns of the fornix that looks like a wish bone and at the base of the columns is the mammillary bodies
AC is shown superficial to it is the columns of the fornix that looks like a wish bone and at the base of the columns is the mammillary bodies
Coronal 3d FSPGR
Coronal 3d FSPGR
Anterior commissure Caudate nucleus Column of fornix Putamen
Anterior commissure
Caudate nucleus
Column of fornix
Putamen
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Ant commissure in yellow
Ant commissure in yellow
T2
T2
AC: Anterior commissure; BSC: Brachium of superior colliculus; Cgh: Cingulum, hippocampal; Cgs: Cingulum, subcallosal; CM: Centromedian nucleus; CN: Caudate nucleus; DLF: Dorsal longitudinal fasciculus; FF: Fields of Forel; FR: Fasciculus retroflexus; Fxc: Fornix, column; Fxpe: Fornix, precommissural; GP: Globus pallidus; Hb: Habenula; HC: Habenular commissure; Hi: Hippocampus; Hia: Hippocampus, alveus; Hif: Hippocampus, fimbria; ICa: Internal capsule, anterior limb; ICp: Internal capsule, posterior limb; ICrI: Internal capsule, retrolenticular; IFG: Inferior frontal gyrus; IFO: Inferior fronto-occipital fasciculus; LGN: Lateral geniculate nucleus; LV: Lateral ventricle; MFB: Medial forebrain bundle; MTT: Mammillothalamic tract; OR: Optic radiation; PC: Posterior commissure; PHG: Parahippocampal gyrus; Pu: Putamen; UF: Uncinate fasciculus; V3: Third ventricle; VL: Ventral lateral nucleus; VPL: Ventral posterior lateral nucleus; VPM: Ventral posterior medial nucleus; ZI: Zona incerta.
AC: Anterior commissure; BSC: Brachium of superior colliculus; Cgh: Cingulum, hippocampal; Cgs: Cingulum, subcallosal; CM: Centromedian nucleus; CN: Caudate nucleus; DLF: Dorsal longitudinal fasciculus; FF: Fields of Forel; FR: Fasciculus retroflexus; Fxc: Fornix, column; Fxpe: Fornix, precommissural; GP: Globus pallidus; Hb: Habenula; HC: Habenular commissure; Hi: Hippocampus; Hia: Hippocampus, alveus; Hif: Hippocampus, fimbria; ICa: Internal capsule, anterior limb; ICp: Internal capsule, posterior limb; ICrI: Internal capsule, retrolenticular; IFG: Inferior frontal gyrus; IFO: Inferior fronto-occipital fasciculus; LGN: Lateral geniculate nucleus; LV: Lateral ventricle; MFB: Medial forebrain bundle; MTT: Mammillothalamic tract; OR: Optic radiation; PC: Posterior commissure; PHG: Parahippocampal gyrus; Pu: Putamen; UF: Uncinate fasciculus; V3: Third ventricle; VL: Ventral lateral nucleus; VPL: Ventral posterior lateral nucleus; VPM: Ventral posterior medial nucleus; ZI: Zona incerta.
Three-dimensional magnetic resonance rendering demonstrates a superior view of the anterior commissure (AC). 1: anterior limb of the AC; 2: lateral (temporal) limb of the AC; 4: corpus of the AC.
Three-dimensional magnetic resonance rendering demonstrates a superior view of the anterior commissure (AC). 1: anterior limb of the AC; 2: lateral (temporal) limb of the AC; 4: corpus of the AC.