Cerebral White Matter
Dr. Maha Zakaria
Lecturer of anatomy and embryology
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1. Define types of white matter of the cerebral
hemisphere.
2. List major association bundles of the brain.
3. Locate the internal capsule, identifying its different
parts, fibers passing in each part, blood supply &
predict effect of lesion.
4. List commissures of the brain.
5. Identify parts of corpus callosum.
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Section 1
Association
fibers
Section 2
Projection
fibers
Section 3
Commissural
fibers
Clinically significant points will be addressed between sections
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Cerebral
white matter
Association
fibers
Commissural
fibers
Projection
fibers
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MRI tractography and research
Dr. Ghada is speech and language specialist, she
has been carrying out a research at the MRI unit
at Demerdash hospital.
Her research study targeted the abnormal
formation of some fasciculi in dyslexic children.
Can u identify the fasciculi that Dr. Ghada
targeted?
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Section 1
Association fibers
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Long association
Fibers that connect different regions in the same hemisphere
Short fibers: connect adjacent gyri in the
short association
same lobe
Long fibers:
connect between lobes.
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3. Uncinate
Fronto-occipital
the frontal
the occipital
temporal
lobes.
It runs
at a
4.
bundle:bundle:
connectsconnects
Wernicke‟s
area (inlobe
the to
temporal
lobe) and
to Broca‟s
area
(in the
frontal
deeper
plane than
superior
longitudinal
lobe); forming
an arch
around
the lateralbundle,
sulcus.and is considered as part of it separated from it by the fibers
of the corona radiata.
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The cingulum is part of…....
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MRI tractography and research
Can u identify the fasciculi that Dr. Ghada
targeted?
1. Uncinate (arcuate)
2. fronto-occipital
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Section 2
Projection fibers
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Include fibers that connect the cerebral cortex with lower centers
(diencephalon, brain stem, and spinal cord).
It forms the corona radiata and internal capsule. Its fibers are either ascending
or descending.
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Internal capsule
Broad sheet of white matter runs between three masses of grey matter
Ascending and descending fibers
PARTS:
• ANTERIOR LIMB
• GENU
• POSTERIOR LIMB
• RETROLENTIFORM
• SUBLENTIFORM
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Ascending and descending fibers
Anterior limb: between lentiform and head of caudate
Anterior thalamic radiation (remember??)
Frontopontine fibers
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Genu :
Corticonuclear fibers
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Posterior limb: between thalamus and lentiform
Corticospinal
(UL ANT, LL POST)
• Frontopontine
• Corticorubral (red nucleus; motor learning)
• Superior thalamic radiation
(sensory radiation) from
VPLN & VPMN of thalamus
to sensory cortex (SI & SII).
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Retrolentiform part
Behind lentiform nucleus
Contains optic radiation +
parietopontine and occipitopontine fibers.
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Sublentiform parts
Below lentiform Nucleus
Contains auditory radiation +
Temporopontine and parietopontine fibers
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Applied anatomy
The internal capsule is frequently involved in cerebrovascular accidents.
Because so many fibers are grouped in a small area, even a small
hemorrhage can cause wide spread effects on the contralateral side of the
body (total hemiplegia, hemianesthesia & UMN cranial nerve (VII, XII)
affection).
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Section 3
commissural fibers
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Mrs. Naglaa complained that her 2-years-old
son shows mildly delayed motor milestones,
the pediatrician ordered brain MRI he
suspected post-encephalitic lesions, after
seeing the MRI, the pediatrician assured Mrs.
Nagla that her son had a benign yet unusual
condition.
Can u predict the condition diagnosed by the doctor?
If the corpus callosum was transected later in life,
would the prognosis differ?
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Commissural fibers: fibers that connect corresponding areas across the midline
1. The corpus callosum
Largest commissure
Relations:
Inferiorly: fornix & septum
pellucidum
Superiorly: falx cerebri & anterior
cerebral arteries
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Corpus callosum: Parts
Rostrum: Connects the orbital surfaces of the
two frontal lobes.
Genu: connects medial and lateral surfaces of
frontal lobes.
Forms forceps minor
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Body : Connects wide area:parietal, temporal
occipital lobe
Fibers intersect with corona radiata
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Splenium : expanded posterior part
Fibers form forceps major in occipital lobe and
medial wall of posterior horn
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Tapetum : fibers of post. body and ant.
Splenium
Form roof and lateral wall of posterior horn of
lateral ventricle
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1
2
3
4
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Anterior commissure:
In lamina terminalis ant. To column of fornix
Anterior bundle connects anterior
perforated substance and olfactory
tracts
Posterior bundle connects temporal
gyri
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Posterior commisure:
In posterior lamina of pineal stalk
Connects:
Pretectal nuclei
Superior colliculi
Mlb
Iv
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Habenular commisure:
In superior lamina of pineal stalk
Connects habenular nuclei
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Hippocampal commissure:
Commissure of fornix
The fornix is a type of:
Commissural fibers?
Projection fibers?
Association fibers?
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Thank you
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