RCSI Forebrain, Third Ventricle & Related Structures PDF

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Forebrain, Third Ventricle & Related Structures Class Year 2 Semester 1 Lecturer Dr. Vijayalakshmi S B Date 30/10/2024 2 PHINEAS GAGE “Brain damage changed...

RCSI Royal College of Surgeons in Ireland Coláiste Ríoga na Máinleá in Éirinn Forebrain, Third Ventricle & Related Structures Class Year 2 Semester 1 Lecturer Dr. Vijayalakshmi S B Date 30/10/2024 2 PHINEAS GAGE “Brain damage changed him completely. He was no longer Gage”. Gage was a serious, industrious & energetic person. Following injury to prefrontal lobe of cerebral cortex he became- Impulsive, hostile & thoughtless of others. Perseverative (stereotyped movements) Could not plan actions. IMPORTANCE OF PREFRONTAL CORTEX IN THE CONTROL OF HUMAN AGGRESSION LEARNING OBJECTIVES Identify the major functional regions of the cerebral cortex and explain their function Describe the ventricular system and the production and circulation of the cerebrospinal fluid Describe the structures related to the third ventricle Identify the hypothalamus, pituitary gland and pineal gland Discuss the position and function of the thalamus EMBRYOLOGY TELENCEPHALON DIENCEPHALON – CEREBRAL HEMISPHERES – PINEAL GLAND – THALAMUS – HYPOTHALAMUS – BASAL NUCLEI (GANGLIA) – SUBTHALAMIC NUCLEI  ANATOMY OF THE BRAIN: INTERNAL ANATOMY ‘Ancient brain’ ‘Primate thinking brain’ ‘Mammalian feeling brain’ Contains: Brainstem, Contains: Cortex Contains: Hippocampus, Cerebellum Pineal gland, Hypothalamus, Functions: Sensory Perception, Thalamus, Amygdala Functions: 4F’s: Flight, Fight, Spatial Reasoning, Conscious Feed & Fornicate thought, Motor commands, Functions: Emotions, Intellectual memory Learning, Emotional memory, Selfish brain - Spirituality individual survival Predicting brain – Social brain – helps the community survive community survival and thrive Courtesy: Dr. Adrian Dervan CEREBRAL HEMISPHERES BRODMANN AREAS Find the approximate location of these functional areas of the cortex on the left half of the cerebral hemisphere By kind permission of the Medical Gallery of Blausen Medical 2014  FUNCTIONS OF THE CEREBRAL CORTEX Primary sensory cortex Sensation tracts from Primary motor cortex thalamus Perceiving opposite side Perceiving 3D and Sensory association area Influence motor areas Taste Smell Planning Vision Organisation Personality Hearing Inhibition LOBES LOBES BODY REPRESENTATION ON MOTOR & SENSORY CORTICES - HOMUNCULUS For both the motor and sensory cortices, the parts of the body are inverted on the cortex (e.g., face at the bottom and trunk at the top)  DOMINANT LATERAL CEREBRAL HEMISPHERES – CONTROL AREAS SPEECH AREA AND ITS CONNECTIONS Broca’s area S1 and S2 Posterior language Arcuate area fasciculus A1 and A2 V1 and V2 Wernicke’s area 14  DOMINANT HEMISPHERES – LANGUAGE AREAS AND APHASIA Broca’s area Motor aphasia (non- fluent) Arcuate fasciculus Speech laboured, words missing Dysarthria Patient is aware of problem Broca’s area Wernicke’s Also – agraphia area Large lesion – face, arm affected Wernicke’s area Sensory aphasia (fluent) Auditory incomprehension Large lesion – can’t read Confuse words, use similar sounding words Not aware of the problem  DOMINANT HEMISPHERES – LANGUAGE AREAS AND APHASIA Doctor: “What kind of work do you do?” Ms. Wern: (Speaks fluently) “Rain, yesterday, tico, to, white I gotta go. She-her, angry he come, I don’t know why, always up and down, up and down, tira-tira, about around here.” Fluent, melody may be intact, plenty of function words, few content words, listener can make no sense of what is said, “word salad” neologisms (new words). “WERNICKE’S APHASIA”. No insight into the problem. 16  DOMINANT HEMISPHERES – LANGUAGE AREAS AND APHASIA Doctor: “What kind of work do you do?” Mr. Tan: (Patient speaks slowly) “Bread…..cakes…cookie….cash… chocolates....people…people” Non-fluent, slow, lacks melody, plenty of content words, no function words, listener often gets a gist of what is said, “telegraphic” speech. Could be irritable and disturbed due to insight into his problem. “BROCA’S APHASIA” 17  What is wrong here? Doctor: “What kind of work do you do?” Mr. Archie: “I have a conivience store. I sell gitracee…… citregea…..what to say…that thing you smoke cigarttte…cigarette..” Fluent, halting at times, paraphasia (producing wrong syllables), good comprehension. “CONDUCTION APHASIA”- Damage to the arcuate fasciculus that connects Wernicke’s with Broca’s area. 18 RESULT OF DAMAGE TO AREAS OF LATERAL CEREBRAL HEMISPHERES  NON-DOMINANT HEMISPHERE HOLISTIC- SHAPES, SPATIAL AWARENESS, “MUSICAL” MEDIAL CEREBRAL HEMISPHERE https://clinicalgate.com MEDIAL CEREBRAL HEMISPHERE MEDIAL CEREBRAL HEMISPHERE LESIONS  FIBRE TYPES ASSOCIATION – interconnect cortical sites within one cerebral hemisphere PROJECTION – pass between the cerebral cortex and subcortical structures COMMISSURAL – run from one cerebral hemisphere to the other FIBRE TYPES Commissural fibres Association fibres Includes: Includes: a. Corpus callosum a. Uncinate fasciculus b. Anterior commissure b. Arcuate fasciculus c. Posterior commissure c. Cingulum d. Fornix d. Superior longitudinal e. Habenular commissure fasciculus e. Inferior longitudinal fasciculus f. Fronto-occipital fasciculus  Splenium PARTS OF CORPUS CALLOSUM of corpus callosum Genu of corpus callosum Rostrum of corpus callosum Body of Sagittal section corpus Model through the BRAIN callosum MB31  Body Genu Splenium Rostrum PARTS OF CORPUS CALLOSUM MIDLINE SAGITTAL SECTION Pre-central Central Post-central gyrus sulcus gyrus Thalamus Corpus Cerebellum collosum Lateral ventricle midbrain pons medulla FIBRE TYPES Projection fibers Includes: a. Internal capsule b. Corona radiata c. Cortico-spinal tract d. Sensory tracts INTERNAL CAPSULE VENTRICULAR SYSTEM VENTRICULAR SYSTEM Ventricular system Consist of: x2 lateral ventricles (1st & 2nd) 3rd ventricle 4th ventricle interventricular foramen (of Monro) Connects 1st & 2nd (Lateral ventricles) to 3 rd ventricle Cerebral aqueduct (of Sylvius) Connects 3rd to the 4th ventricle CSF is secreted by the choroid plexus.  VENTRICULAR SYSTEM Lateral ventricles are cavities of cerebral hemispheres CSF flows from the lateral ventricle through the interventricular foramen (of Monro) to the third ventricle Third ventricle is the cavity of the diencephalon  VENTRICULAR SYSTEM Lateral ventricles are cavities of cerebral hemispheres CSF flows from lateral ventricle through interventricular foramen (of Monro) to third ventricle Third ventricle is cavity of diencephalon  CEREBROSPINAL FLUID Functions Shock Absorber Pressure Regulator Keeps Brain Buoyant Transports Removes Nutrition for the brain 150ml is the volume 500ml/day produced.  CHOROID PLEXUS Produces Cerebrospinal Fluid (CSF) Arteries in subarachnoid space Arteries invaginate pia No brain tissue between pia and ependyma at these points So, blood is separated from CSF only by vessel wall, pia, ependyma Passive diffusion and active excretion Produced in each ventricle but mostly in lateral ventricle CHOROID PLEXUS Eppendymal cells  FLOW OF CEREBRAL SPINAL FLUID Foramen of Munro Cerebral Aqueduct (of Sylvius) From 4th Ventricle: Posteriorly – Median aperture (foramen of Magendie) Laterally – Lateral aperture (foramina of Luschka)  LATERAL VENTRICLES C-shaped, with a posterior spur Anterior horn - frontal lobe Body - parietal lobe Posterior horn - occipital lobe Inferior horn - temporal lobe Choroid fissure - medial wall Septum pellucidum (from under the surface of the corpus callosum to the upper surface of the fornix) separates lateral ventricles in the midline LATERAL VENTRICLES HYDROCEPHALUS  THIRD VENTRICLE Slit-like space between Anterior boundary = lamina – right and left hypothalamus terminalis – right and left thalamus Floor = optic chiasma, infundibulum, mamillary bodies CLINICAL VIGNETTE A 61-year-old man with hypertension was seen in the emergency department, having apparently suffered a stroke. A neurologist was called and made a complete examination of the patient. The patient was conscious and was unable to feel any sensation down the right side of his body. There was no evidence of paralysis on either side of the body, and the reflexes were normal. He was admitted to the hospital for observation. Three days later, the patient appeared to be improving, and there was evidence of the return of sensation to the right side of his body. The patient, however, seemed to be excessively sensitive to testing for sensory loss. Although the patient experienced very severe pain with the mildest stimulation, the threshold for pain sensitivity was raised, and the interval between applying the pinprick and the start of the pain was longer than normal; also, the pain persisted after the stimulus had been removed. Later, it was found that heat and cold stimulation excited the same degree of discomfort. The neurologist made the diagnosis of analgesia Dolorosa involving the left thalamus.  THALAMUS Right and left thalamus may be stuck together (interthalamic adhesion) – Not a commissure All general sensory Thalamus information goes through (ventral posterior nucleus, e.g., spinothalamic tract, dorsal columns, trigeminothalamic tract) Posterior part = pulvinar has lateral geniculate body laterally = visual relay medial geniculate body below = auditory relay  MAJOR SENSORY PATHWAYS Afferent nerves – in cranial Thalamus and spinal nerves General senses 3 neurones o (recall: SENS-OR-Y) 2 Sensation types Touch/Proprioception: o Dorsal columns Pain & Temperature o Spinothalamic tract  MAJOR SENSORY PATHWAYS Afferent nerves – in cranial Thalamus and spinal nerves General senses 3 neurones o (recall: SENS-OR-Y) 2 Sensation types Touch/Proprioception: o Dorsal columns o Decussates in the medulla Pain & Temperature o Spinothalamic tract *touch/proprioception pathways Gracilis – lower body/trunk Cuneatus – upper body  MAJOR SENSORY PATHWAYS Afferent nerves – in cranial Thalamus and spinal nerves General senses 3 neurones o (recall: SENS-OR-Y) 2 Sensation types Touch/Proprioception: o Dorsal columns o Decussates in medulla Pain & Temperature o Spinothalamic tract o Decussates immediately  MAJOR SENSORY PATHWAYS Touch/Proprioception: Pain & Temperature o Dorsal columns o Spinothalamic tract o Decussates in medulla o Decussates immediately  MAJOR SENSORY PATHWAYS Reflex Arcs  SENSORY CORTEX Thalamic Lesion: Contralateral hemianaesthesia with thalamic pain.  PINEAL GLAND Located in epithalamus – just above the superior colliculus Secretes melatonin At night – sleep (activated by darkness) ? role in sexual activity (onset of puberty) Pineal gland Calcified from 30s on Midline shift on x-ray (may lie slightly to left) REVISION Lateral ventricles – anterior horn Septum pellucidum Internal capsule – anterior limb  Corona radiata Head of caudate nucleus Internal capsule Putamen Globus pallidus Putamen + globus pallidus = Lentiform nucleus Thalamus Third ventricle Hippocampus REFERENCES