Cranial Fossa: Brain and Spinal Cord Clinical Anatomy Tony Serino, Ph.D.

Cranial Fossa: Topic Objectives Be able to describe the distribution of grey and white matter in the brain and spinal cord Be able to describe the arrangement of the meninges and the differences between cranial and spinal meninges Be able to describe blood flow to and from the cranial fossae Be able to describe normal CSF flow Be able to deduce consequence of CSF blockages Be able to identify the major parts and regions of the brain and spinal cord and their development Be able to describe the functions of selected areas of the brain Understand brain blood flow and be able to predict vascular changes to the circle of Willis when an obstruction occurs in a single vessel Be able to describe Cranial Nerve location and function Be able to predict functional loss with CN paralysis

Central Nervous System (CNS) Gray vs. White matter Protection of CNS Meninges CSF flow Brain Development Selected structures Spinal cord

Cranial Fossa Anterior Middle Posterior

CNS (Central Nervous System) Brian and spinal cord Displays gray and white matter Gray matter are areas of CNS with many cell bodies of neurons present (little myelinated nerve fibers) White matter are area of CNS with few cell bodies but many myelinated nerve fibers Protected by bone and membranes

Gray and White Matter Since the cerebrum and cerebellum outgrow their cores, gray matter ends up on outside of both structures.

Meninges Dura Mater –outermost; tough, fibrous CT In brain, divided into two layers (periosteal and meningeal) In spine, only one layer with fat filled space above the layer called the epidural space Arachnoid –middle; web-like appearance Potential space between Dura and arachnoid is the subdural space Pia Mater –innermost, delicate membrane fused with CNS surface Space between Pia and Arachnoid is the subarachnoid space

Meninges of the Spinal Cord Epidural space Pia mater Arachnoid Dura mater Meninges Subdural space Subarachnoid space Dorsal Root Ganglion Centrum

Brain Meninges

Extensions of Dura Mater hold brain in cavity Sellar diaphragm (not shown)

Venous Sinuses of Cranium Superior Sagittal Inf. Sagittal Straight Transverse Cavernous Sigmoid

Lateral Venous Lacunae Arachnoid villi

Middle Meningeal Artery Maxillary A.

Brain Ventricles

Choroid Plexus

CSF (cerebral-spinal fluid) Flow

Hydrocephalus Blockage of CSF flow can lead to severe brain and/or head enlargement. In an adult, such swelling would be fatal.

Brain Development Structures Functional Areas

Neural Tube forming

Neural Tube

Brain Vesicles

Flexures and Cerebral Cortex Growth

Major Divisions of Brain Brain Stem = midbrain + pons + medulla

Brain Anatomy (req’d)

Projections vs. Commissures

Functional Areas of Cerebrum

Primary Motor and Somatosensory Gyri

Basal Nuclei: cerebral nuclei Putamen and Globus Pallidus Subthalamic nuclei and the Substantia nigra are usually included

Reticular Formation Extends along length of brain stem; used in maintaining alertness while awake; also includes motor nuclei such as centers for Cardiac, Respiratory and Vasomotor control.

RAS receives inputs from eye, ear and general sensation to maintain alertness

Limbic System: functional system; responsible for emotion and memory Cingulate Gyrus Fornix Mammillary body

Hypothalamus Control of Pituitary

Posterior Pituitary

Anterior Pituitary

Pineal Gland Plays a major role in circadian rhythm control through its sympathetic connection to the hypothalamus Melatonin increases at night and decreases during daylight Implicated in the control of major life changes (such as the onset of puberty and adulthood

Internal Carotid Artery

Blood Supply (Circle of Willis) Ant. Cerebral Ant. Communicating Middle Cerebral Internal Carotid A. Post. Communicating Post. Cerebral Basilar A. Vertebral A.

Cranial Nerves

CN I: Olfactory Nerve covered by meninges and contain glial cells Cribiform plate damage after trauma could lead to CSF leakage (runny nose after head trauma) Pathway: Bulbtract  med and lat. stria prepiriform and amygdala

CN II: Optic Nerve Covered by meninges Leaves by optic canal Pathway: nervechiasma  tracts  lat. geniculate and sup. colliculus  optic radiation to occipital lobe

CN III: Occulomotor Nerve Superior Orbital Fissure Midbrain Pons Oculomotor N. (III) Ciliary ganglion Inferior Rectus muscle Oblique muscle Superior Rectus muscle Medial Rectus Levator Palpabrae Parasympathetic Motor fibers CN III: Occulomotor Nerve Originates from brain stem: midbrain Leaves via sup. orbital fissure Path: occulomotor nucleus  muscles : levator palpebrae, sup., medial, inf. rectus, and inf. oblique. Separate branch from Edinger-Westphal nuclues  ciliary ganglion  parasym innervation to iris sphincter and ciliary muscle. Palsy –leads to ptosis, diplopia, dilated pupil; gaze is “down and out”; pupil involvement usually due to increase cranial pressure due to surface location of fibers in nerve

CN IV: Trochlear Nerve Originates from brain stem: midbrain Complete decussation in midbrain Nucleus to Sup. oblique, runs the longest distance in cranial vault Passes through sup. orbital fissure In injury, affected eye is higher and deviated medially, head tilts away from lesion; hardest to diagnose

CN V: Trigeminal Nerve

CN VI: Abducens Nerve Originates from brain stem: pons  goes to lateral rectus m. Passes through sup. orbital fissure Injury: affected eye deviates medially (crosseyed look) patient may turn head to compensate

CN VII: Facial Nerve

CN VIII: Vestibulocochlear Nerve

CN IX: Glossopharyngeal Nerve

CN X: Vagus Nerve

CN XI: Accessory Nerve

CN XII: Hypoglossal Nerve