Cerebrum: Midsagittal View

Key Structures:

Brainstem
Cerebellum
Diencephalon
Corpus callosum
Cerebral lobes

Brainstem

From superior to inferior:

Midbrain
Pons, anterior-lying: basis
Medulla oblongata: pyramidal tracts

Additional points of interest

  • The brainstem transitions into the spinal cord, inferiorly.
  • The tectum lies along the upper posterior surface of the brainstem.
  • CSF funnels through the cerebral aqueduct (of Sylvius) in the upper brainstem.
  • The fourth ventricle is the collection of CSF in the mid-brainstem level.

The cerebellum

  • The cerebellum packs its vast surface area into the tightly-packed posterior/inferior skull (the posterior fossa).

The diencephalon

  • Comprises numerous thalamic regions, most notably the thalamus and hypothalamus.

We can remember its central location by the clinical syndrome of central herniation, which typically first involves the diencephalon. And we can remember its autonomic function (from the hypothalamus) by the clinical syndrome of diencephalic autonomic storm (or dysautonomia).

The corpus callosum

  • C-shaped, prominent white matter pathway, connects the bilateral cerebral hemispheres.

We can remember its function by corpus callosotomy (aka “split brain” surgery), which involves transection of the corpus callosum (and commissures), usually to stop the spread of seizures.

Clinical correlation, see callosal dysgenesis

Cerebral Lobes

The oft-forgotten limbic lobe surrounds the corpus callosum and diencephalon.

The additional cerebral lobes are the:

Frontal lobe (anteriorly)
Parietal lobe (behind it)
Occipital lobe (posteriorly)
Temporal lobe (inferiorly)

Sulci

  • The central sulcus distinguishes the frontal lobe from the parietal lobe.

Show in your diagram that the primary motor cortex extends along the medial surface of the brain, as does, the primary sensory cortex does, as well.

  • The parieto-occipital sulcus distinguishes the parietal and occipital lobes.
  • The calcarine sulcus lies along mid-section of the occipital lobe.
  • The primary visual cortex lies along the banks of the calcarine sulcus.

Key Gyri

  • The cingulate gyrus lies within the superior limbic lobe.
  • The uncus is the antero-inferior gyral thumb.

Prominent structures from superior to inferior:

  • The fornix, which wraps around the thalamus, which underlies it.
  • The interthalamic adhesion, which is the medial thalamic bump.
  • The hypothalamus, beneath the thalamus (it surrounds the 3rd ventricle) and comprises numerous nuclei, including:
  • The mammillary bodies, just anterior to the brainstem.
  • A portion of the pituitary gland (anteriorly).
  • The pineal gland (of the epithalamus) lies along the posterior diencephalon.

To help remember the position of the pineal gland above the tectum consider that pineal tumors can compress the tectum, which causes vertical gaze palsy, called Parinaud’s syndrome.

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