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Lab 5: White Matter and the Ventricles

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1 Lab 5: White Matter and the Ventricles
Wed. February 25th, 2015 Describe the anatomic correlates pertinent to the production, flow and reabsorption of cerebrospinal fluid. Identify the following structures of the limbic system: fornix, amygdala, mammillary bodies and hippocampus. Identify intercortical, commissural and projection fibers on sections of the brain. Identify the internal capsule and the associated fibers in the anterior limb, posterior limb and genu. Name the major cerebrospinal fluid (CSF) containing structures, including the lateral ventricles and the intracranial cisterns created in the subarachnoid space. Christopher Ramnanan, Ph.D.

2 The CSF containing ventricle system
Lateral ventricles (LV): Associated with the caudate nucleus Anterior Horn: associated w/ Head caudate nucleus Body: associated w/ Body of caudate nucleus Inferior and Posterior Horns: associated w/ Tail of caudate nucleus Inferior Horn Anterior Horn Body Posterior (Occipital) Horn Cerebral Aqueduct: associated w/ midbrain 3rd Ventricle: associated with thalamus 4th Ventricle: Associated with pons, medulla, cerebellum

3 Production and Flow of CSF
CSF is produced (~500 mL/day, adult) by the choroid plexus in all four ventricles. Typical description of flow: Lateral ventricles  IV Foramen of Munro  3rd ventricle  Cerebral Aqueduct  4th ventricle  exits Foramen of Magendie (Median Plane) and Foramen of Luschka (Bilateral)  Cisterna Magna to circulate around CNS CSF fluid is mainly reabsorbed in the venous sinus system system via arachnoid granulations (most easily seen in the superior sagittal sinus. Choroid Plexus, Lat. Ventr. Choroid Plexus; 3rd Ventr. Choroid Plexus, 4th Ventr.


5 Prominent CSF cisterns
Quadrigeminal (superior) cistern: posterior to midbrain Interpeduncular cistern (chiasmatic cistern): located anterior to the midbrain; contains optic chiasm Cisterna manga (cerebellomedullary cistern): largest pool; located b/w the cerebellum and the medulla; receives CSF from Luschka/Magendie Pontine (pre-pontine) cistern: located anterior to cistern

6 These cisterns can best be approximated (where the CSF pools would have been, in life) in sagittal brain specimens with dura intact. The cisterns are useful landmarks in sagittal clinical images, as are the ventricle structures. MRI Ventricles and CSF cisterns – Sagittal view

7 The cortex has white matter connections with other parts of the CNS including:
Association fibers: connections to other regions of cortex within the same hemisphere; Projection fibers: connections to subcortical structures (thalamus, basal ganglia, brainstem, spinal cord) and Commissural fibers: connections to cortex within contralateral hemisphere We won’t go into any detailed discussion of any particular association fibers, but we will discuss important commissural and projection fibers over the next few slides.

8 Prominent Commissural Structure: The Corpus Callosum
Genu Rostrum Splenium Note: -Corpus callosum larger in females than males; may relate to females > males in terms of multitasking -Agenesis of corpus callosum is a common congenital malformation (may affect motor milestones, social behaviour and cognitive functions in children; often misdiagnosed) -Corpus callosum surgical resection sometimes used in epileptic patients to limit incidents of secondary seizures Genu Splenium

9 FYI links: The story of Kim Peek, who inspired the autistic character in the movie Rain Man: Patients with partial or complete lack of corpus callosum share their experiences: How corpus callosum disorders can be diagnosed:

10 Prominent Projection Structure: The Internal Capsule
Includes most fibers (descending motor, ascending sensory) that travel between cortex and subcortical structures (thalamus, brainstem, spinal cord). We will identify structures passing through the anterior limb, the genu, and the posterior limb of the internal capsule. The optic radiations are associated with posterior aspect of the posterior limb.

11 Internal Capsule, Coronal View
Corona radiata fibers will continue as the internal capsule. Some fibers of the internal capsule descending from the precentral gyrus (ie. motor tracts) will continue as cerebral peduncles in midbrain. Corona radiata Note: In this coronal plane, you can see that internal capsule is landmark that separates the thalamus and head of the caudate nucleus (medial) from the lentiform nucleus (not well observed in this particular cut).

12 Transverse View Through Internal Capsule: Major Components
Ant. Limb passes b/w caudate head and lentiform nucleus Transverse View Through Internal Capsule: Major Components Anterior limb -frontopontine tracts -thalamic radiations to prefrontal cortex Genu (the bend) -Corticobulbar motor tracts supplying face Posterior Limb 1) descending corticospinal motor tracts supplying limbs 2) thalamic somatosensory radiations to primary somatosensory cortex 3) auditory radiations (medial geniculate nucleus to primary auditory cortex in temporal lobe) 4) optic radiations (lateral geniculate nucleus to primary visual cortex in occipital lobe) Post. Limb passes b/w caudate head and lentiform nucleus

13 The Internal Capsule includes:
Sensory information (except olfaction) relayed from thalamus to cortex (thalamic or thalamocortical radiations ). Selected fibers include: Thalamus to Frontal Lobe: Prefrontal Cortex (Ant. Limb) Thalamus to Parietal Lobe: Primary Somatosensory Cortex (Post Limb) Thalamus to Temporal Lobe: Primary Auditory Cortex Thalamus to Occipital Lobe: Primary Visual Cortex Post Limb Genu Ant Limb

14 L A H The Internal Capsule includes:
Descending motor tracts from the primary motor cortex (precentral gyrus): Corticopontine tracts (to pons) Corticobulbar tracts (to medulla) Corticospinal tracts (to spinal cord) H

15 The Internal Capsule includes:
Ascending sensory information that will be relayed (via the thalamus) to the primary somatosensory cortex (postcentral gyrus): The dorsal column/medial leminscus tract (fine touch/proprioception) The spinothalamic tract (pain/temperature)

16 The Internal Capsule includes:
The auditory radiations (from medial geniculate nucleus to primary auditory cortex of the temporal lobe; this is conceptual) Auditory radiations

17 The Internal Capsule includes:
The optic radiations (lateral geniculate nucleus to primary visual cortex of the occipital lobe) Medial (nasal side) optic tract fibers cross Most fibers terminate in Thalamus (lateral geniculate bodies) Axons are relayed via optic radiations to visual cortex of occipital lobe

18 The Limbic System Today’s objectives include selected structures that were previously introduced to you, in great detail, by Dr. Lau in the Psychiatry Block (Week 2; ‘Neuropsychiatry Workshop’ Session): hippocampus,fornix, amygdala, mammillary bodies, and cingulate gyrus (previously an objective in Lab 2). The limbic structures function in emotion, memory, motivation, and learning.

19 Note: you are only responsible for identifying the cingulate gyrus
Note: you are only responsible for identifying the cingulate gyrus. Note that this gyrus spans several lobes and is associated with corpus callosum.

20 Note: Olfactory input projects to amygdala

21 Inf. Horn, Lat. Vent. Hippocampus
Note: you can use inferior horn, lat ventricle to ID tail of the caudate and the hippocampus (grey matter above and below ventricle, respectively).

22 Note: you can use the uncus to approximate location of amygdala

23 Fornix Mammillary Body Corpus Callosum (cut) Hippocampus Hippocampus
The fornix is a white matter structure leaving the hippocampus that projects mainly to the mammillary bodies (hypothalamus) which, in turn, mainly projects to the thalamus via mammillothalamic tracts. Fornix Mammillary Body Corpus Callosum (cut) Hippocampus Hippocampus Thalami Fornix Thalamus Fornix Lat. Ventricle, Inf. Horn. Mammillary Body


25 * * * * * Main Afferents Main Efferents Cingulate cortex
Association cortex, thalamus Hippocampus Cingulate cortex, Association cortex Mammillary bodies (via fornix), Amygdala Mammillary Bodies Thalamus Amygdala Hypothalamus

26 FYI: The legacy of H.M. -In 1953, underwent bilateral medial temporal lobectomy to treat epilepsy -Epileptic seizures were effectively controlled but significant impact on aspects of memory, while other aspects of memory remained intact. -Maybe one of the most studied brains in history

27 Dr. Lau (in psychiatry) and Dr
Dr. Lau (in psychiatry) and Dr. Grimes (this slide, shown earlier this week) described limbic functions associated with the basal ganglia. While we studied the motor circuit of the basal ganglia, note that there is a limbic circuit as well.

28 Fornix Ant. Horn, Lat Vent. Inf. Horn of Lat. Ventricle Hippocampus Internal capsule

29 Lateral View, Lentiform N.
Internal capsule Fornix Ant. Horn, Lat Vent. Lateral View, Lentiform N. Post. Horn of Lat. Ventricle Inf. Horn of Lat. Ventricle Hippocampus Digital Anatomy Resource: ID -ventricles -limbic system structures -internal capsule components

30 Digital Anatomy Resource: ID
-ventricles -grey matter (including basal ganglia from last week) -white matter (internal capsule components, and what fibers run through each part)

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