Neurosurgery notes/Anatomy/Cortex/Frontal lobe

Frontal lobe

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Cortex
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Foix–Chavany–Marie syndrome
SMA syndrome
Primary motor cortex
Frontal lobe examination

General

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A diagram of a brain AI-generated content may be incorrect.
  • Aka: Lobus frontalis

Gyri

  • Superior frontal gyri F1
  • Middle frontal gyri F2
    • What clinical finding is seen when there is a lesion of the posterior part of the middle frontal gyrus?
      • Conjugate eye deviation toward the ipsilateral side. This is area 8, the cortical lateral conjugate gaze center. Stimulation of this area results in eye deviation toward the contralateral side
  • Inferior frontal gyri F3
    • 3 parts
      • Pars Orbitalis
        • Forms the frontal operculum.
        • Occasionally, the diagonal sulcus (sulcus diagonalis of Eberstaller) can divide the opercular part of the inferior frontal gyrus into two parts.
        • Orbital part is continuous with the basal surface of the frontal lobe, where it merges with the lateral orbital gyrus.
        • The triangular and opercular parts form together the motor language area of Broca
      • Pars Triangularis
        • May be indented from above by a radiate sulcus (sulcus radiatus of Eberstaller).
        • The triangular and opercular parts form together the motor language area of Broca
      • Pars Opercularis
  • Precentral gyrus (gyrus precentralis)
  • Subcentral gyrus (central operculum or rolandic operculum)

Sulci

  • Superior frontal sulci f1
  • Inferior frontal sulci f2
  • Central sulcus
    • Usually does not reach the lateral sulcus (Sylvain fissure)
    • Is separated from lateral sulcus by a short gyrus, the subcentral gyrus (gyrus subcentralis)
      • Delimited in front and behind by the anterior and posterior subcentral sulci (sulcus subcentralis anterior and-posterior)
  • Frontomarginal sulcus (sulcus frontomarginalis of Wernicke)
    • Is fairly constant
    • Found at the frontal pole
    • Connected posteriorly with the middle frontal sulcus.
    • Has two branches
      • Deep medial branch that borders the frontopolar gyri
        • Separates the frontomarginal sulcus from the medial frontal gyrus
      • Shallow lateral branch
        • Separates the frontomarginal sulcus from the orbital part of the inferior frontal gyrus

Boundaries

  • It extends from the frontal pole to the central sulcus posteriorly.
  • It is separated from the temporal lobe below by the sylvian fissure.
  • On the medial surface, it is separated from the corpus callosum by the callosal sulcus.
  • It is separated from the parietal lobe on the medial surface by a line running downward from the upper end of the central sulcus to the corpus callosum.
  • It is bounded on the lateral surface by the central sulcus (posteriorly) and the superior hemispheric border (superiorly).

Surfaces

Lateral Surface (Convexity)

  • The convexity is formed by the superior, middle, and inferior frontal gyri, and the precentral gyrus.
  • The precentral gyrus is a vertical gyrus parallel to the central sulcus, bounded in front by the precentral sulcus.
  • The area anterior to the precentral sulcus is divided into three horizontal convolutions by the superior and inferior frontal sulci: the superior, middle, and inferior frontal gyri.
  • The inferior frontal gyrus is located between the sylvian fissure and the inferior frontal gyrus, and it is divided (from anterior to posterior) into the pars orbitalis, pars triangularis, and pars opercularis by the anterior horizontal and anterior ascending rami of the sylvian fissure.
  • The pars opercularis and adjacent pars triangularis are frequently referred to as Broca’s speech area.

Frontopolar area (area frontopolaris)

  • Part of the medial and lateral surfaces of the frontal lobe
  • Three gyri
    • Superior
    • Middle
    • Inferior
  • That are clearly separated by limiting sulci, interposed between the superior frontal gyrus and the frontomarginal gyrus.
    • Bludau et al. (2014) distinguished two cytoarchitectonically and functionally distinct areas: the lateral frontopolar area 1 (Fp1) and the medial frontopolar area 2 (Fp2).

Medial Surface

  • This surface is formed predominantly by the medial surface of the superior frontal gyrus, the anterior half of the paracentral lobule, and the cingulate gyrus.
  • The superior frontal gyrus is separated from the cingulate gyrus by the cingulate sulcus.
  • Anteriorly, the superior frontal gyrus and cingulate gyrus blend into the paraterminal and paraolfactory gyri, situated below the rostrum of the corpus callosum.

Basal (Orbital) Surface

  • The entire surface facing the orbital roof belongs to the frontal lobe.
  • This surface is concave from side to side and rests on the cribriform plate, orbital roof, and the lesser wing of the sphenoid bone.
  • It is formed by the gyrus rectus (medial strip of cortex) and the orbital gyri (larger lateral part).
  • The olfactory sulcus, which overlies the olfactory bulb and tract, separates the gyrus rectus from the orbital gyri.
  • The orbital gyri are divided by the roughly H-shaped orbital sulcus into anterior, medial, posterior, and lateral orbital groups.
Images
  • 1, Anterior orbital gyrus;
  • 2, Lateral orbital gyrus;
  • 3, Medial orbital gyrus;
  • 4, Posterior orbital gyrus;
  • 5, Rectus gyrus;
  • 6, Pars orbitalis;
  • 7, Transverse gyrus;
  • 8, Insular pole.
  • The arrows indicate anterior insular cleft.
  • The arrowheads indicate posteromedial limb of the orbital sulcus. *, posteromedial orbital lobule, just anterior to the lateral olfactory stria and lateral to the olfactory sulcus.
A close-up of a brain AI-generated content may be incorrect.
Basal view of the right frontal lobe.
  • 1, Anterior orbital gyrus
  • 2, Olfactory tract
  • 3, Lateral orbital gyrus
  • 4, Medial orbital gyrus
  • 5, Rectus Gyri
  • 6, Insula
  • 7, Anterior perforating substance
  • 8, Insula pole
  • 9, Amygdala
  • 10, Carotid bifurcation
  • 11, Hippocampal head
A close-up of a brain AI-generated content may be incorrect.
Basal view of the cerebrum.
  • 1, Anterior orbital gyrus
  • 2, Medial orbital gyrus
  • 3, Rectus gyrus
  • 4, Pars triangularis
  • 5, Posterior orbital gyrus
  • 6, Pars opercularis
  • 7, Anterior short gyrus of the insula
  • 8, Anterior perforating substance
  • Black arrow heads, Limen insula
A close-up of a human body AI-generated content may be incorrect.
Frontobasal view of the right hemisphere. The anterior part of the planum polare has been retracted inferiorly to display the anterior aspect of the insular pole.
  • a, Olfactory bulb;
  • b, Straight gyrus;
  • c, d, e, f, Medial, anterior, posterior, and lateral olfactory gyri;
  • g, Olfactory tubercle;
  • h, Optic tract;
  • i, Lateral geniculate body;
  • j, Medial geniculate body;
  • k, Pulvinar;
  • 1, Olfactory sulcus;
  • 2, Medial orbital sulcus;
  • 3, Transverse orbital sulcus;
  • 4, Lateral orbital sulcus.
A diagram of a human brain AI-generated content may be incorrect.
Gyri and sulci on the orbital part of the frontal lobe, shown for the basal surface of the cerebral hemisphere

Deep anatomy

  • The frontal horn of the lateral ventricle is positioned deep to the inferior frontal gyrus.
  • The anterior wall and roof of the frontal horn are formed by the genu of the corpus callosum; the floor is formed by the rostrum of the corpus callosum; and the lateral wall is formed by the head of the caudate nucleus.
  • The anterior limb of the internal capsule is located lateral to the frontal horn and caudate head and carries frontopontine fibers.
  • The uncinate fasciculus connects the anterotemporal lobe with the orbitofrontal area. Its fibers run through the ventral external and extreme capsules in the temporal stem.
  • The cingulum (a bundle of association fibers) begins deep to the paraolfactory and paraterminal gyri on the medial frontal surface and courses deep to the cingulate gyrus.
  • The superior longitudinal fasciculus arches backward from the frontal lobe, positioned along the upper and lateral border of the lentiform nucleus and insula. Frontal fibers of this tract form a compact fasciculus in the depth of the inferior and middle frontal gyri.
Images
  • 1, Head of the caudate nucleus;
  • 2, Genu of the corpus callosum;
  • 3, Rostrum of the corpus callosum;
  • 4, Inferior continuation of the cingulate gyrus;
  • 5, Inferior continuation of the medial frontal gyrus;
  • 6, Lateral orbital gyrus;
  • 7, Posterior orbital gyrus;
  • 8, Medial orbital gyrus;
  • 9, Rectus gyrus and the olfactory tract.
  • Superior rostral sulcus is located between the 4 and 5,
  • Inferior rostral sulcus is located between the 5 and 9.
  • Posteromedial limb of the orbital sulcus is located between the 7 and 8.
  • Olfactory sulcus is located superiorly to the olfactory tract
A close-up of a brain AI-generated content may be incorrect.
A coronal cut at the level of the planum sphenoidale, just anterior to the head of the caudate nucleus has been made.
  • The column of fornix and the genu of the corpus callosum can be easily mistaken. The fornix is at the anterior border of the Foramen of munro and the genu of the corpus callosum is even more anterior to it.
A close-up of a human brain AI-generated content may be incorrect.
A coronal cut was performed at a level between the optic chiasm and planum sphenoidale
  • 1, Caudate nucleus;
  • 2, Thalamus, choroidal fissure, and thalamostriate vein;
  • 3, Internal capsule, transition between the anterior limb and the genu;
  • 4, Foramen of Monro and column of fornix;
  • 5, Putamen;
  • 6, Globus pallidus;
  • 7, Lamina terminalis and hypothalamus;
  • 8, Optic chiasm.
  • *, Anterior commissure
 
A close-up of the inside of a human body AI-generated content may be incorrect.
Coronal cut performed at the level of the optic chiasm (at the anterior perforated substance).
 

Arterial Supply

  • Middle Cerebral Artery (MCA):
    • The MCA supplies the orbitofrontal, prefrontal, and precentral cortical areas.
    • The most common pattern involves two stem arteries supplying the frontal lobe: one supplies the orbitofrontal, prefrontal, and precentral areas, and the other supplies the central area.
    • MCA branches may overlap onto the lateral part of the orbital surface.
  • Anterior Cerebral Artery (ACA):
    • The ACA supplies the cortex and adjacent white matter of the medial surface from the frontal pole posteriorly.
    • On the lateral surface, the ACA supplies the superior frontal gyrus and the superior parts of the precentral and central gyri.
    • On the basal surface, the ACA supplies the gyrus rectus, olfactory bulb and tract, and the medial part of the orbital gyri.
    • The orbitofrontal artery supplies the gyrus rectus and the medial part of the orbital surface of the frontal lobe.
    • The frontopolar artery supplies portions of the medial and lateral surfaces of the frontal pole.
    • The internal frontal arteries supply the medial and lateral surfaces of the superior frontal gyrus as far posteriorly as the paracentral lobule.

Reference