Paediatric Neuroanatomy

Hemispheres, Lobes & Gyri

Commisures.

WM bundle connecting hemispheres.

- Corpus Callosum  
- Anterior Commisure  
- Posterior Commisure  
- Habenular Commisure  
- Hippocampal Commisure

Frontal Lobe

Emotion
Motor = Posterior Part = Precentral Gyrus = Primary Motor Cortex.

Lateral surface

1. Superior Frontal Gyrus  
2. Middle Frontal Gyrus  
3. Inferior Frontal Gyrus    
    * ***Broca's Area*** = Inferior LEFT Frontal Gyrus.   
    * PRODUCTION    
    * *Pars Opercularis & Pars Triangularis*

Inferior surface.

1. Gyrus Rectus ( Medial ). *Adjacent to Olfactory bulbs*  
2. Medial Orbital Gyri   
3. Lateral Orbital Gyri ( Lateral )

Temporal Lobe

Lateral Margin.

- Superior Temporal Gyrus  
- Middle Temporal Gyrus  
- Inferior Temporal Gyrus

Inferior Margin

- Occipitotemporal Gyrus = *Fusiform Gyrus*  
- Parahippocampal Gyrus

Other Parts

- Amygdala = Anterior aspect of Temporal horn of Lateral Ventricle  
- Uncus = Medial projection of Temporal horn  
- Transverse Temporal Gyrus *aka Heschl's Gyrus*  
    -   Between Posterior Insula ==> Superior Temporal Gyrus.   
        -   Auditory Processing  
    -   Wernicke's Area = Posterior LEFT Superior Temporal Gyrus   
        -   RECEPTION

Connection between Wernicke's & Broca's : Arcuate Fasiculus.

Parietal Lobe

Superior Part
Inferior Part

- Angular Gyrus  
- Supramarginal Gyrus

Occipital Lobe

Cuneus

- Part behind the parieto-occipital fissure and the *Calcarine fissure*.

Calcarine Fissure

- Just off Midline & vaguely Ant-post. 
- lined with **Primary Visual Cortex**

Deep Strutures

Globi Palldi --> Hypothalami -->[Merge midline]-->Infundibular stalk.

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Midline Structures

Corpus Callosum

Parts: Rostrum, Genu, Body, Isthmus, Splenium.
'Homotopic' = connects the same part of the cerebral hemispheres together.
Contains white matter tracts.

- 'Forceps Minor' => Genu = Frontal pole connectors. 
- 'Forceps Major' => Splenium = Occipital pole connectors.

Pineal Gland
Directly above the Posterior Commisure.

Tectal Plate
Most posterior part of midbrain.

-2 Superior colliculi = Vision.  
-2 Inferior colliculi = Auditory.

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Ventricles & CSF Spaces

'Cistern': Occurs when pia mater and arachnoid are not closely aligned.

- Perimesencephalic Cisterns : around midbrain.  
    - Crural Cisterns : anterolateral.   
    - Ambient Cisterns : lateral.   
    - Quadrigeminal: posterior.  
- Prepontine Cistern.  
- Cerebellopontine Angle Cistern.  
- Lateral Medullary Cisterns. ( Lateral to medulla )  
- Cisterna Magna ( below cerebellar vermis )

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Myelination ¹

White Matter Bundles

- *Commisural*: Joins to opposite hemisphere.  
- *Association*: Joins within the same hemisphere.  
- *Projection*: Extend to deep grey, brainstem, cerebellum.

Is divided into:

1. Juxtacortical.  
2. Deep White Matter   
    - Periventricular is a subset.

Unmyelinated White Matter

- Very high water content (80%) thus,  
- T1: LOW, T2: HIGH

Myelinated White Matter

- = Proteolipid 70% Lipid, 30% Protein thus,  
- T1: HIGH, T2: LOW.  
- The water content is still 70% though.

But Transition Phase

- have lipid precursors thus HIGH T1,   
- but not yet hydrophobic thus high water and HIGH T2.  
- Thus, T1 shortening is seen about 3 months before decline in T2.

Myelination timetable.

Read Normal Myelination Atlas (here)[../papers/Myelination_Paed.pdf]

	Term	2 mths	4 mths	6 mths	9 mths	12mths	18mths
Internal Capsule	Spot in post PLIC	Most PLIC	PLIC +/- Angle	Into ALIC	Whole IC
Corpus Callosum			Isthmus & Body	Splenium	+/- Genu	Whole Genu
Cerebral Hemispheres		+/- Optic Radiation		Most occipital. Some Frontal	J/C in Occiput	J/C in Frontal	T2 high in J/C Frontal.

J/C = Juxtacortical. Myelination correlates with development of function. Juxtacortical WM in the frontal lobe is still maturing up to 2yrs on T2 and microstructurally to adolescence.

Terminal Myelination

as per Roxana in Grainger and Allison.

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1. Choudri, Asim. Pediatric Neuroradiology: Clinical Practice Essentials. Thieme 2017. ↩