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NEUROANATOMY REVIEW

NEUROANATOMY REVIEW. David Jho. CEREBRAL CTX. BRODMANN’S AREAS. 4. 3,1,2. 6. 5,7. 8. 9. 40. 39. 10. 22. 19. 45,44. 18. 41,42. 28. 17. 34. 11. 12. BRODMANN’S AREAS. 8 = Frontal Eye Field 6 = SMA & Premotor ctx 5,7 = PPC (apraxia, dom. side) 4 = Primary motor ctx

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NEUROANATOMY REVIEW

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  1. NEUROANATOMY REVIEW David Jho

  2. CEREBRAL CTX

  3. BRODMANN’S AREAS 4 3,1,2 6 5,7 8 9 40 39 10 22 19 45,44 18 41,42 28 17 34 11 12

  4. BRODMANN’S AREAS 8 = Frontal Eye Field 6 = SMA & Premotor ctx 5,7 = PPC (apraxia, dom. side) 4 = Primary motor ctx 3,1,2 = Primary somatosensory ctx 41,42 = Primary auditory ctx (Transverse gyrus of Heschl) 45,44 = Broca’s speech area (Inf Frontal Lobe; expressive dysprosody) 22 = Wernicke’s speech area (arcuate fasciculus connect to Broca’s; receptive dysprosody) 40 = Supramarginal gyrus (Rt/Lt confusion, dyscalculia, understanding speech) 39 = Angular gyrus (dyslexia & dysgraphia) 4 3,1,2 6 5,7 8 9 40 39 10 22 19 45,44 18 41,42 28 17 34 11 12

  5. BRODMANN’S AREAS 39, 40 = Inf parietal lobe (Gerstmann’s syndrome) on dominant side a) Rt/Lt confusion b) dyscalculia c) finger agnosia d) dyslexia & dysgraphia e) lower quadrantanopia (visual radiations to cuneus) Parietal lobe, non-dominant hemisphere (Sup or Inf parietal lobes) a) contralateral sensory neglect & astereognosis b) construction apraxia c) lower quadrantanopia (visual radiations to cuneus) 9,10,11,12 = Prefrontal ctx Post part of orbital gyrus = smell Uncus = serves as part of primary olfactory ctx (medial temporal lobe) 34 = Primary olfactory ctx (medial temporal lobe—seizures can have smell aura) 4 3,1,2 6 5,7 8 9 40 39 10 22 19 45,44 18 41,42 28 17 34 11 12

  6. LIMBIC SYSTEM

  7. PAPEZ CIRCUIT (Limbic System) HIPP Septal area Hypothal Fornix Stria terminalis VAFP/VAPP Fornix Ventral AmygdaloFugal Pathway Ventral AmygdaloPetal Pathway Mamillary body Amygdala Mamillothalamic tract Olfactory, Sensory, Autonomic Ant nuc of thalamus Wernicke’s Encephalopathy (Thiamine/Vit B1 defic) Ant limb of internal capsule 1) Nystagmus 2) Ataxia 3) Mental status change Cingulate gyrus Perforant pathway Cingulum Korsakoff’s confabulatory syn Entorhinal ctx 1) Mem loss & confabulation

  8. Mediodorsal nuc of the thalamus (associated with Ant nuc) Orbitofrontal ctx (associated with HIPP) Ansa lenticularis = VA Fugal Pathway

  9. Klüver-Bucy Syndrome (bilateral ablation of ant temporal lobes including amygdala) • Docility • Hypersexuality • Hyperphagia • Visual agnosia AMYGDALA—coordinates behavioral & emotional responses to complex sensory input by integrating somatosensory and viscerosensory information. Output via Stria Terminalis posteriorly by tail of caudate and arches over thalamus to anterior hypothalamus. Output via Ventral Amygdalofugal pathway (VAFP) to Caudate/Septal Area.

  10. HYPOTHALAMUS • Homeostasis (autonomic, endocrine, & limbic systems) • Half of hypothalamus is enough

  11. Ant Hypothal Nuc (dissipates heat, parasympathetic) Post Hypothal Nuc (conserves heat, sympathetic) Parvocellular PVN PVN & SON (produce oxytocin & ADH/vasopression, destruction causes DI) SUPRAOPTICO-HYPOPHYSIAL TRACT Magnocellular PVN Preoptic area (Medial Preoptic Nuc) (sexually dimorphic, regulates gonadotropic hormones) Suprachiasmatic nuc (direct retinal input, circadian rhythms) Lat Nuc (appetite center, stim induces eating, destruction causes starvation) Dorsomedial Nuc (stim causes obesity & savage behavior) Ventromedial Nuc (satiety center, stim stops eating, destruction causes obesity & savage behavior) Arcuate Nuc (DOPA-ergic neurons inhib prolactin release) TUBERO- INFUNDIBULAR TRACT

  12. HYPOTHALAMIC FIBER SYSTEMS Fornix From HIPP to mamillary nuclei (then Mamillothalamic tract to Ant Thal Nuc) Medial Forebrain Bundle (MFB) • in lat hypothalamus, lat to fornix; can be damaged in hypothal injury • unmyelinated, major connection b/n cerebral ctx & BS • no synaptic relay through thalamus • has monoaminergic neurons from the locus coeruleus (NE), raphe nuclei (5-HT), and ventral tegmental area (DA). Hypothalamo-spinal tract Descending autonomic fibers for sympathetic neurons (thoracic intermediolateral horn) and parasympathetic neurons (sacral lateral horn) Lesion or interruption above T1 can cause Horner’s syndrome (miosis, ptosis, anhidrosis, & apparent enophthalmos)

  13. HYPOTHALAMIC FIBER SYSTEMS Stria terminalis Stria terminalis is the major pathway of Amygdala to hypothalamus & septal area. STRIA = STRANDS (Sup to fornix & divides caudate from thalamus) Lamina terminalis (from optic chiasm to rostral 3rd ventricle; closure of ant neuropore) LAMINA = LAYER Stria medullaris thalami (hypothalamus & septal area in roof of 3rd ventricle inf to fornix to thalamus & epithalamic habenular nuclei; relay from limbic forebrain to midbrain reticular formation) MEDULLARIS is also in the MEDULLA Stria medullaris of 4th ventricle (central sulcus to Inf Cereb Ped; arcuate nuc of pyramids) Sulcus Limitans (divides Alar & Basal plates) SULCUS = GROOVE

  14. HYPOTHALAMIC FIBER SYSTEMS (strands)

  15. HYPOTHALAMIC FIBER SYSTEMS Ant neuropore (anencephaly) vs Post neuropore (spina bifida) Lamina terminalis (layer)

  16. HYPOTHALAMIC FIBER SYSTEMS (medial & also in medulla)

  17. HYPOTHALAMIC FIBER SYSTEMS

  18. EMBRYOLOGIC DEVELOPMENT Neural Tube (CNS, pregang ANS) Neural Crest (PNS including DRG, postgang ANS) Sulcus Limitans (divides Alar & Basal plates) Alar plate (sensory), Basal plate (motor) Rhombencephalic lip (in roof of 4th ventricle becomes Cerebellum)

  19. EMBRYOLOGIC DEVELOPMENT PRIMARY VESICLES SECONDARY VESICLES Telencephalon (lateral ventricles) Prosencephalon Diencephalon (3rd ventricle) Mesencephalon Mesencephalon (cerebral aqueduct) Metencephalon (upper 4th ventricle) Rhombencephalon Myelencephalon (lower 4th ventricle, central canal)

  20. THALAMUS BLOOD SUPPLY 1. PCA (post circulation) 2. PCOM (ant circulation) 3. Ant Choroidal a (ICA)

  21. = ANT-MED (limbic) = ANT-LAT (EPS) = POST (sensory) = NON-SPECIFIC (relay)

  22. VA/VL (GP+SN) Ant+MD (Papez) VPL (sensory--body) VPM (sensory--head) LGN (vision) MGN (hearing) Pulvinar (visual sensory association) Intralaminar CM (very diffuse to cerebral ctx, ends in layer I for cortical excitability) Reticular (GABA-ergic to thal) = ANT-MED (limbic) = ANT-LAT (EPS) = POST (sensory) = NON-SPECIFIC (relay)

  23. Mamillary bodies Cingulate gyrus Prefrontal ctx

  24. GP, SN (EPS) Area 6 Area 4 GP, SN, cerebellum (EPS + dentatothalamic tract) Area 4 + EPS

  25. Integration of somesthetic, visual, & auditory Areas 18,19 Areas 3,1,2 Areas 41,42 Sensory--body Hearing Sensory--face Vision Area 17

  26. Caudate Caudate Fornix VA (VL) VA (VL) Ant Ant Interthalamic adhesion Cerebral peduncle Cerebral peduncle Mamillary bodies Ant Ant Pulvinar Pulvinar VL VL MD Pineal gland CM CM MD MD Sup colliculus LGN LGN VPL VPL MGN MGN VPM VPM Midbrain Zona Incerta STN Pons LD or DL LP

  27. HIPPOCAMPUS HIPPOCAMPAL FORMATION (3-layered archicortex; declarative mem) a) Dentate gyrus—HIPP input & output to HIPP pyramidal cells b) Hippocampus proper or Cornu Ammonis (CA)—to fornix then septal area c) Subiculum—to fornix then mamillary nuc Alzheimer’s Disease affects neurons in Nuc Basalis of Meynert (ACh), Locus Coeruleus (NE), Entrorhinal ctx, and CA1/Subiculum of HIPP.

  28. HIPPOCAMPUS Mammillary bodies Postcommissural Fornix Fimbria of Fornix (connects bilateral CA) Alveus 6-layer NEOCORTEX 3-layer ARCHICORTEX vs Schaeffer collaterals CA3 CA1 CA4 DENTATE GYRUS Perforant path Entorhinal ctx (with pyriform ctx are paleoctx) SUBICULUM Alvear path

  29. Dentate gyrus has afferents entirely within HIPP formation. CA1 projects to Subiculum and precommissural fornix. CA3 projects to CA1 and precommissural fornix. CA4 (hilus of dentate gyrus) receive afferents from dentate and project to bilateral dentate (hippocampal commissure). Subiculum provides main efferents to POST-COMMISSURAL FORNIX (to thalamus and hypothalamus).

  30. EPS SYSTEM

  31. Pyr system (CS tract) UMN lesion LMN lesion 1. Weakness 2. Spasticity 3. Inc tone 4. No atrophy 5. Babinski 1. Weakness 2. Dec DTR 3. Dec tone 4. Atrophy 5. Downgoing toes Cerebellum EPS (Basal Ganglia) Intention tremor Ataxia (fall towards lesion, gait & trunk dystaxia, dysrhythmokinesia, dysdiadochokinesia, dysmetria) Nystagmus Dec DTR/tone ipsilaterally Asthenia (mm tire easily) • Chorea (Huntington’s, Syndenham’s) • Athetosis (choreoathetosis in HD, Tardive dyskinesia when antipsychotics block DA receptors & make super-sensitive) • Hemiballismus (stroke) • Parkinson’s vs Diffuse Lewy Body Dz (resting tremor, bradykinesia, truncal instability, dementia)

  32. Lenticular nuc = Put + GP Striatum/Neostriatum = Put + Caud Corpus striatum = Put + Caud + GP Glutamate GABA (Glycine in SC) Input from Ctx--Net excitation Input from D1 recep—Net excitation DIRECT PATHWAY Ctx Striatum GPi/SNr VA/VL thalamus Ctx Parkinson’s D1 recep SNc Input from Ctx—Net inhibition Input from D2 recep—Net excitation INDIRECT PATHWAY Ctx Striatum GPe STN GPi/SNr VA/VL thalamus Ctx Parkinson’s D2 recep SNc

  33. Striatum (GABAergic neurons) have both D1 recep (Gs; contain excitatory Substance P) and D2 recep (Gi; contain inhibitory Enkephalin). Net LOSS of excitation in Parkinson’s Dz. Pallidotomy destroys segments of GPi to reduce inhibition of thalamus (interrupts direct & indirect pathways). GPi and GPe are usually always on. Input from Ctx--Net excitation Input from D1 recep—Net excitation DIRECT PATHWAY Ctx Striatum GPi/SNr VA/VL thalamus Ctx Parkinson’s D1 recep SNc Input from Ctx—Net inhibition Input from D2 recep—net excitation INDIRECT PATHWAY Ctx Striatum GPe STN GPi/SNr VA/VL thalamus Ctx Parkinson’s D2 recep SNc

  34. GPe is constantly on. In Huntington’s chorea, the striatum (ACh & GABAergic medium spiny neurons) are destroyed so GPe overstimulates Ctx. Damage to STN results in Hemiballismus due to decreased stim of thalamic inhibition to Ctx. Input from Ctx--Net excitation Input from D1 recep—Net excitation DIRECT PATHWAY Ctx Striatum GPi/SNr VA/VL thalamus Ctx Parkinson’s D1 recep SNc Input from Ctx—Net inhibition Input from D2 recep—net excitation INDIRECT PATHWAY Ctx Striatum GPe STN GPi/SNr VA/VL thalamus Ctx Parkinson’s D2 recep SNc

  35. CEREBELLUM Functional vs Anatomical Divisions

  36. Cerebellar Synonyms • FLOCCULONODULAR LOBE = Vestibulocerebellum. • VERMIS = Medial zone or part of Spinocerebellum. • PARAVERMIS = Intermediate zone or part of Spinocerebellum. • CEREBELLAR HEMISPHERES = Lateral zone or Cerebrocerebellum or Pontocerebellum.

  37. Cerebellar Function • FLOCCULONODULAR LOBE = balance & eye movement. • VERMIS = balance & axial motor functions. • PARAVERMIS = distal motor execution. • CEREBELLAR HEMISPHERES = motor planning.

  38. Cerebellar Peduncles 1. Sup Cerebellar Ped (dentatothalamic tract, VSCT) 2. Middle Cerebellar Ped (pontocerebellar fibers) 3. Inf Cerebellar Ped (OlivoCT, Dorsal SpinoCT, CCT, vestibulocerebellar tract) - Spine to cerebellum

  39. Motor Ctx (corticopontine & CS tracts) VL (thalamus) Corticopontine fibers MOLECULAR LAYER Basket Stellate Pontine nuc Dentatothalamic tract (Sup Cereb Ped) Pontocerebellar tract (contralat) Red Nuclei (rubrospinal tract) PARALLEL FIBERS PURKINJE LAYER Cereb Deep Nuc Dentate Emboliform Fastigial Globose Purkinje GOLGI LAYER MOSSY FIBERS CLIMBING FIBERS Golgi Spinocerebellar Pontocerebellar Vestibulocerebellar (cerebellar & vestibular nuc) Granule ION Olivocerebellar tract to CLIMBING FIBERS Vestibulospinal tract

  40. 4 Cerebellar Deep Nuclei 5 Types ofCerebellar Cells (know if excit or inhib; know if projects out of cerebellum or not)

  41. Cerebellar Deep Nuclei receive excitatory afferents fromClimbing fibers and Mossy fibers(collaterals on their way to the Granule layer). Purkinje cell(only ones that project out of ctx) inhibitory fibers from Cerebellar Ctx to Cerebellar Deep Nuclei. Climbing fibers from Inf Olivary Nuc via Inf Cerebellar Ped.Pontocerebellar fibersvia Middle Cerebellar Ped. Granule cell(only excitatory) endings (Parallel Fibers) go to Molecular layer but not out of Cerebellar Ctx.Stellate, Basket, & Golgi cells(inhibitory) do not project out of Cerebellar Ctx either.

  42. Flocculo-nodular lobe projects to Medial and Lateral Vestibular Nuclei. Medial Vestibular Nuclei assist coordinating eye movement with body. Lateral Vestibular Nuclei assist postural control. Be careful not to confuse Dentate nuclei (cerebellum) and Dentate gyri (HIPP).

  43. Rubrospinal tracts (gross mvmts unlike CS tracts) & crosses immed in midbrain. Rt cerebellum to Lt Red Nucleus to Rubrospinal tracts crossing left-to-right to innervate Rt arm & leg. Cerebellar tests = finger-to-nose (dysmetria & intention tremor), foot tap/heel shin, pronator drift with poor adjustment, dysdiadochokinesia, nystagmus on extreme gaze. Romberg test = vision, vestibular, DC-ML. (not SC tract, which is unconsc proprio).

  44. BV’s & CN’s

  45. Berry aneurysms (ACOM, MCA, PCOM, basilar) asymptomatic unless large or rupture (possible death) rupture—SAH, hemorr stroke (seizures, HCP) worst HA of life (10/10) ADPKD, Ehlers-Danlos, Marfan’s Uncus = where Amygdala is located Pituitary adenoma Acoustic neuroma (Schwannoma) at CPA

  46. ICA-MCA aneurysm can put pressure on side of optic chiasm. Basilar tip aneurysm can put pressure on CN3’s. Lat striate or Lenticulostriate aa of cerebral hemorrhage (internal capsule). Occlusion of PCA distal to PCOM can result in Ant choroidal to Post choroidal aa. Labyrinthine a from AICA or Basilar a. Post Spinal a from PICA or Vertebral a.

  47. Autoregulation allows constant blood flow over wide bp range (local metabolite control). Pupillary light reflex is CN2 afferent and CN3 efferent. CN2 lesion preserves a consensual reflex. CN3 lesion causes blown-pupil, down-and-out eye, droopy eyelid, & efferent loss. Corneal blink reflex is CN5 (V1) afferent and CN7 efferent. Ankle jerk = S1 Knee ext = L2,3,4 Brachiorad = C5 Biceps = C6 Triceps = C7 Abdominal = T8-T12 Babinski = L5-S1

  48. Internal Capsule BLOOD SUPPLY ANT LIMB = ACA (medial striate aa) + MCA (lateral striate aa) GENU = ICA (Ant Choroidal a) POST LIMB = ICA (Ant Choroidal a) + MCA (lateral striate aa)

  49. Epidural lens, Subdural falx, Subarachnoid (ventricles), Intraparenchymal bleeds Scalp infections down through valveless emissary vv. Pineal tumors (Perinaud’s syn) block cerebral aqueduct and/or impose on sup colliculus

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