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Structure

Frontal lobe

Not medically reviewed · Content last updated · 2 min read ·

This is the date the draft was written, not a medical review date.

The frontal lobe is the largest cerebral lobe, concerned with voluntary movement, speech production, executive function, judgement and behaviour. It contains the primary motor cortex and, in the dominant hemisphere, Broca area.

Terminologia Anatomica (Latin): Lobus frontalis · Open in the 3D atlas

Location

It lies in the anterior cranial fossa and extends back to the central sulcus, which separates it from the parietal lobe; the lateral sulcus forms its inferior border with the temporal lobe. Its gyri are the precentral, superior, middle and inferior frontal gyri, with orbital and medial surfaces.

Structure

Main functional areas: primary motor cortex (Brodmann area 4, precentral gyrus, somatotopic homunculus), premotor and supplementary motor areas (area 6), frontal eye field (area 8), Broca area (areas 44 and 45, inferior frontal gyrus, dominant hemisphere, usually left) and the prefrontal cortex. The leg area lies on the medial surface.

Blood supply

The middle cerebral artery supplies the lateral surface, including the face and arm motor areas and Broca area; the anterior cerebral artery supplies the medial surface and the leg area, with orbitofrontal parts supplied by both. Venous drainage is to the superior sagittal sinus and superficial middle cerebral vein.

Innervation

Afferents come mainly from the thalamus (ventral anterior, ventral lateral and mediodorsal nuclei), basal ganglia loops, and parietal and temporal association cortex. Efferents form the corticospinal and corticobulbar tracts and project to the striatum, thalamus, pons and brainstem; callosal fibres connect the hemispheres.

Function

It plans and initiates voluntary movement, controls conjugate eye movements towards the opposite side, produces fluent speech, and supports working memory, attention, planning, impulse control, social behaviour and personality.

Clinical correlations

Contralateral hemiparesis follows motor cortex lesions: MCA infarcts affect face and arm more than leg, ACA infarcts the leg more than the arm. Dominant inferior frontal lesions cause Broca (non-fluent) aphasia with preserved comprehension. Prefrontal damage produces abulia, disinhibition and personality change; frontal release signs and gaze deviation towards an irritative or destructive lesion may occur, and frontal seizures are common.

Common exam points

  • Borders: central sulcus (posterior) and lateral sulcus (inferior); precentral gyrus is Brodmann area 4.
  • Broca area (areas 44 and 45) lies in the dominant inferior frontal gyrus; lesion gives non-fluent aphasia with intact comprehension.
  • MCA stroke: face and arm weakness; ACA stroke: leg weakness and abulia.
  • Frontal eye field lesion deviates gaze towards the lesion; seizures deviate it away.
  • Frontal lobe damage: disinhibition, apathy, perseveration and primitive reflexes (grasp, palmomental).

References

  1. Drake RL, Vogl AW, Mitchell AWM. Gray's Anatomy for Students. Elsevier — Tier 3 (textbook)
  2. Kandel ER, Koester JD, Mack SH, Siegelbaum SA. Principles of Neural Science. McGraw-Hill, 6th edition (2021) — Tier 3 (textbook)
  3. Haines DE, Mihailoff GA. Fundamental Neuroscience for Basic and Clinical Applications. Elsevier, 5th edition (2018) — Tier 3 (textbook)

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