Neuroanatomy and CSF Flow

• Objectives include describing the CNS organization, identifying brain lobes and fissures, naming gyri and sulci, discussing lobe functions, explaining gray and white matter arrangement, detailing CNS-supplying vessels, describing the choroid plexus, tracing CSF circulation, explaining the CSF role, describing the internal carotid and vertebral-basilar arterial systems, relating somatotopy to blood supply occlusions, describing the Circle of Willis, explaining blood supply syndromes, detailing venous drainage, and explaining the blood-brain barrier

CNS Orientation

• The planes of orientation include coronal, horizontal, and sagittal
• The directions are caudal, dorsal, ventral, superior, inferior, anterior, and posterior

Gross Anatomy

• Surface landmarks include gyri (ridges), sulci (grooves between ridges), and fissures (deep sulci)
• The brain is divided into the forebrain (telencephalon and diencephalon)
• The telencephalon includes the cerebrum and basal ganglia
• The diencephalon includes the thalamus, hypothalamus, and subthalamus
• The brainstem consists of midbrain and hindbrain (medulla, pons, and cerebellum)
• The spinal cord is divided into cervical, thoracic, lumbar, and sacral regions

Lateral Surface

• Key structures include the frontal lobe, frontal pole, precentral sulcus and gyrus, central sulcus, parietal lobe, and postcentral gyrus and sulcus
• Additional parts include the temporal lobe, occipital lobe, lateral sulcus (Sylvian fissure), Heschel's gyri, and Wernicke's area
• Broca's area is identified along with the primary motor area, prefrontal cortex, and frontal eye fields

Insula lobe

• The Insula lobe structure inside of the brain

Forebrain Surface Anatomy

• Major sulci and gyri, also known as lobes, include Frontal, Parietal, Occipital, Temporal, Limbic
• The longitudinal fissure separates the cerebral hemispheres
• The central sulcus separates the frontal and parietal lobes
• The lateral fissure separates the frontal and parietal lobes from the temporal lobe
• The parieto-occipital sulcus separates the occipital lobe from parietal and temporal lobes on the medial surface
• The calcarine fissure is on the medial surface of the occipital lobe
• The precentral gyrus is anterior to the central sulcus and is the primary motor area
• The postcentral gyrus is posterior to the central sulcus and serves as the primary somatosensory area

Lateral-Medial

• Structures visible from a lateral-medial perspective include the frontal lobe, precentral gyrus, central sulcus, postcentral gyrus, parietal lobe, parieto-occipital sulcus, occipital lobe, temporal lobe, limbic lobe, corpus callosum, and calcarine fissure.

Inferior-Ventral Structures

• Key components include the frontal and temporal lobes, the optic tract, cerebral peduncles, basal pons, cerebellar hemispheres, and the limbic lobe
• Olives and pyramids are also included in the inferior-ventral structures

Ventral Surface

• Olfactory landmarks include the olfactory fissure, gyrus rectus, uncus, rhinal fissure, primary olfactory cortex, fusiform gyrus, and parahippocampal gyrus

Mid-Sagittal Surface

• Notable features are the superior frontal gyrus, paracentral lobule, cingulate gyrus and sulcus, corpus callosum (genu, body, and splenium), gyrus rectus, and callosal sulcus

Frontal Lobe Functional Anatomy

• Control of voluntary muscle movements relies of the precentral gyrus
• The premotor cortex is responsible for planning coordinated movements and motor learning
• Language production and speech formation is regulated by Broca's area in the left hemisphere
• Higher-order cognitive function is organized by the prefrontal cortex
• Emotional processing/social awareness is regulated by the orbitofrontal cortex
• Working memory, cognitive flexibility, and goal-directed behavior are regulated by the dorsolateral prefrontal cortex
• The frontal eye fields work to control eye movements, and anterior cingulate cortex helps with motivation
• Integrating information to guide movement is coordinated by motor association cortex with complex actions coordinated by the supplementary motor area

Parietal Lobe Functional Anatomy

• Processes sensory information related to touch, pressure, temperature, and pain
• Located just posterior the central sulcus
• The somatosensory association cortex integrates information
• Language and phonological processing are located near the lateral sulcus in the supramarginal gyrus
• Language processing is adjacent to the supramarginal gyrus and the angular gyrus

Temporal Lobe

• Includes the lateral fissure, superior, middle, and inferior temporal gyri, and preoccipital notch

Temporal Lobe Functional Anatomy

• The primary auditory cortex (Heschl's gyrus) processes auditory information
• Language comprehension is the function of Wernicke's area in the left posterior superior temporal gyrus
• Memory and spatial navigation is the function of the hippocampus
• Memory storage and spatial processing is done in the Parahippocampal Gyrus
• The fusiform face area is specialized for facial recognition
• Object recognition is done in the Inferior Temporal Cortex
• The Middle Temporal Gyrus is responsible for language processing and visual perception
• Auditory processing and language is handled in the Superior Temporal Gyrus

Diencephalon

• Landmarks include the thalamus, hypothalamus, and the corpus callosum

Deep Forebrain Structures - Diencephalon

• Thalamus acts as a gatekeeper for the cerebral cortex
• Hypothalamus controls autonomic and endocrine functions and influences emotional and motivational behaviors
• The subthalamus is involved in modulation of voluntary motor activity

Gray vs White Matter

• Gray matter is where the nerve cell bodies reside
• White matter is where the fiber axons reside
• Association fibers are confined to one hemisphere, connecting areas in adjacent gyri or further removed cortical areas
• Commissural fibers originate in the cortex and cross at the midline and connect at the corresponding areas of the corte
• Projection fibers project to and from the cortex

Commissural Pathways

Parts

• Corpus callosum comprises the rostrum, genu, body, and splenium
• There is an anterior and posterior commissure

Function

• The Corpus callosum connects corresponding regions of almost all parts of the cerebral cortex
• The anterior commissure connects structures of the olfactory pathway
• The olfactory pathway includes the frontal cortex, temporal pole, & parahippocampal gyri
• The posterior commissure connects the language processing centers of both cerebral hemispheres

Brainstem

• Sections include the diencephalon, midbrain, pons, medulla, and spinal cord

Cranial Nerves

• Cranial nerves and what they control:
  • CN I (olfactory): Smell
    • Evaluation: Not routinely evaluated
  • CN II (optic): Vision, pupillary light reflexes
    • Evaluation: Pupillary light reflexes (afferent), visual acuity
  • CN III (Oculomotor): Parasympathetic to pupil, motor to most extraocular muscles (medial / superior / inferior rectus, inferior oblique)
    • Evaluation: Pupillary light reflexes (efferent), eye movements
  • CN IV (Trochlear): Motor to superior oblique muscle
    • Evaluation: Eye movements
  • CN V (Trigeminal): Sensory to face, motor to muscles of mastication
    • Evaluation: Sensation to face, muscles of mastication
  • CN VI (Abduces): Motor to lateral rectus muscle
    • Evaluation: Eye movements
  • CN VII (Facial): Motor to muscles of facial expression, parasympathetic to lacrimal gland, taste
    • Evaluation: Blink, various facial movements, tear production
  • CN VIII (Vestibulocochlear): Balance, hearing
    • Evaluation: Body posture, eye movements, hearing, vestibulo-ocular reflex
  • CN IX (Glossopharyngeal): Sensory & motor to pharynx
    • Evaluation: Gag reflex, swallowing
  • CN X (Vagus): Parasympathetic to viscera, sensory & motor to pharynx
    • Evaluation: Gag reflex, swallowing, palatal elevation
  • CN XI (Accessory) Motor to trapezius & sternocleidomastoid muscles
    • Evaluation: Shoulder/neck muscle tone, mass & movement
  • CN XII (Hyoglossal): Motor to tongue muscles
    • Evaluation: Tongue movement & tongue bulk

Cerebral Meninges

• Dura mater (2 layers): serves as periosteum of inner surface of skull and contains the meningeal dura
• Arachnoid mater: lines the dura, bridges over sulci, which contains cerebral spinal fluid while you are alive
• Pia mater: adheres tightly to the surface of your brain

Reflections of the Dura

• Reflections include:
  • Falx cerebri
  • Falx cerebelli
  • Tentorium cerebelli

Meningeal Spaces

• Epidural space: Is extradural
• Subdural space
• Subarachnoid space

The Ventricular System

• The ventricles are cavities within the brain
• Cerebrospinal Fluid (CSF) is produced within the ventricles
• Cerebral aqueduct connects
• The cerebral aqueduct connects the 4th Ventricle is continuous
• CSF flow goes into the subarachnoid space

Lateral ventricles are in each hemisphere - Components include the body, anterior horn, posterior horn and inferior horn

• There is a midline cavity in the 3rd Ventricle
• Located in the pons and medulla is the 4th Ventricle
• Cerebral aqueduct connects to the 3rd Ventricle

Circulation of Cerebrospinal Fluid (CSF)

• CSF IS secreted by the epithelium in cavities of the brain

• CSF moves from cavities into the spinal cord

• CSF moves from the laterals and into the subarachnoid to produce a superior sagittal sinus

• CSF is in ventricles that connect to the 3rd through the the aqueduct

• Spinal fluid is absorbed by the arachnoid villi and transferred to the venous sinus

Normal Stats

• CSF production is 20ml/hour
• CSF amount is 125-150ml
• Normal opening pressure is 6-20 cm H20. This is 25 for people whoe are obese

Dural Venous Sinuses

• Inferior sagittal sinus, as well as superior sagittal sinus. There is also a straight sinus, and Confluence of the sinuses
• Other components include the Transverse sinus, Sigmoid sinus, and Internal jugular vein

Vascular System

• Arterial Supply of the Brain
  • Internal Carotid Arteries
  • Basilar Artery
  • Vertebral Arteries
• Internal Carotid Artery supplies anterior cerebral artery, middle cerebral artery, anterior choroidal artery, and the posterior communicating artery

Internal Carotid Artery

• the ICA comes off the:
  • Brachiocephalic Trunk (Right)
  • Arch of Aorta (Left)
• Carotid bifurcation usually occurs at the superior border of thyroid cartilage = C4 vertebra
• ICA is broken into separate parts (cervical, petrous, cavernous, cerebral)
• ICA components are anterior cerebral artery, middle cerebral artery, anterior choroidal artery

ACA

• Ophthalmic Artery is anterior to ICA with the anterior Cerebral Artery
• MCA are broken into the M1, M2, M3
• M1 - Segment to Sphenoidal segment
• M2 - extends and passes horizontally forward in the lateral (Sylvian) fissure
• M3 - M3 = Cortical segment of MCA

Arteries

• Anterior Cerebral Artery (ACA)

• Middle Cerebral Artery

• Anterior Choroidal Artery

• Posterior Circulation

  • Posterior Circulatory
    • Posterior cerebral artery
    • Superior cerebellar artery -Anterior inferior cerebellar artery -Posterior inferior cerebellar artery -Anterior spinal artery -Posterior spinal artery

• the Posterior Cerebral Arteries and Brainstem connect the Cerebral hemispheres

• Largest vertebral artery is Posterior inferior arterial

• Posterior cerebral artery connect the midbrain

Summary - Lesion Localization

Motor Lesions:

• Lesions in the primary motor cortex result in motor skills like paralysis
• Lesions in the brainstem result in cranial deficits and can lead to problems with motor/sensory movement

Sensory Lesions:

• Lesions in the primary sensory cortex such as the postcentral gyrus
• Lesions in the thalamus can result in sensory deficits to the bdy

Test your knowledge of neuroanatomy, CSF dynamics and related clinical correlations. Questions cover CSF pressure, flow pathways, arterial supply, and the blood-brain barrier. Assess your understanding of brain structures and their functions.