Digital Neuroanatomy

DIGITAL NEUROANATOMY

SKULL, MENINGES, AND SPINAL CORD George R. Leichnetz, Ph.D. Professor, Department of Anatomy & Neurobiology Virginia Commonwealth University 2004

Press the Å and Æ keys on your keyboard to navigate through this lecture Skull The interior of the skull has three depressions: Anterior the anterior, middle, cranial fossa holds frontal and posterior cranial lobe fossae.

Middle cranial fossa holds temporal lobe

Posterior cranial fossa holds cerebellum & brainstem Anterior Cranial Fossa

Crista galli Anterior Cribriform plate of ethmoid transmits Cranial Fossa olfactory nerves (CN I)

Lesser wing of sphenoid

Sphenoid Bone

Anterior clinoid process

Sella turcica holds pituitary gland Optic foramen transmits optic nerve (CN II) Middle Cranial Fossa

Superior orbital Optic foramen fissure transmits transmits optic oculomotor (III), nerve (II) trochlear (IV), and abducens (VI) nerves, plus Middle ophthalmic division of the Cranial Fossa trigeminal (V) nerve

Foramen rotundum transmits maxillary division of V

Foramen ovale transmits mandibular division of V Internal carotid foramen transmits internal carotid artery Foramen spinosum transmits middle menigeal artery Posterior Cranial Fossa

Sella turcica

Foramen rotundum

Foramen ovale

Foramen Internal auditory spinosum meatus transmits CN VII and VIII Internal carotid foramen and carotid canal Petrous ridge of temporal bone

Sigmoid sinus Foramen magnum Jugular foramen Hypoglossal transmits CN canal transmits IX, X, and XI CN XII Meninges and Dural Sinuses The meninges include: dura mater, arachnoid membrane, and pia mater. The dura consists of two layers: an outer periosteal layer that forms the periosteum on the inside of the cranial bone (no epidural space), and an inner layer, the meningeal layer, that gives rise to dural reflections (form partitions). The falx cerebri extends into the longitudinal fissure, separating the cerebral hemispheres. The tentorium cerebelli extends between the cerebellum/ brainstem and the occipital lobe, forming a roof over the posterior cranial fossa. The dural sinuses are endothelial-lined venous channels (“veins”) between the two layers of the dura. The system of venous channels ultimately empties into the internal jugular vein at the jugular foramen. Identify the superior sagittal, inferior sagittal, straight, transverse, and sigmoid sinuses in the meninges, and their impressions inside the skull. Arachnoid villi, knobs protruding into the superior sagittal sinus, allow reabsorption of CSF into the systemic venous circulation. Dura Mater Branches of the middle meningeal artery supply the dura

Arachnoid membrane Arachnoid Membrane

Subarachnoid space

Arachnoid Villi Superior sagittal sinus

Falx cerebri Inferior sagittal sinus

Corpus callosum Straight sinus

Thalamus

Midbrain Confluence of sinuses

Cerebellum Attachment of Pons falx to crista galli The dural sinuses are endothelial-lined venous Medulla channels within the dura. Falx cerebri Tentorial Notch or Incisure

Midbrain Cerebellum

Tentorium Clinoid processes cerebelli serve as attachments for the for the tentorium cerebellum Tentorium cerebelli attaches along the petrous ridge Attachment of tentorium cerebelli Midbrain traverses the along petrous ridge opening in the tentorium cerebelli, the tentorial notch.

Diaphragma sellae has opening for pituitary stalk

Tentorium cerebelli

Clinoid process Straight sinus provides attachment for tentorium

Transverse Midbrain sinus Confluence of sinuses

The brainstem and Cerebellum cerebellum occupy the posterior cranial fossa (infratentorial compartment). Tentorium Cerebelli Removed Revealing Posterior Cranial Fossa (Cerebellum & Brainstem Removed)

Foramen magnum w cervical spinal cord, vertebral arteries

Confluence of Sinuses Transverse Sinus Spinal Cord The spinal cord is about 18” in length, extending from the foramen magnum to vertebral level L2. It expands at levels that give rise to innervation of the upper and lower limbs, the cervical and lumbosacral enlargements respectively. The lower end of the cord tapers to the conus medullaris below which the pia extends as the filum terminale, anchoring the cord inferiorly to the coccyx. About twenty pairs of denticulate ligaments (extensions of pia to dura) anchor the cord laterally within the dural sac. The dorsal and ventral rootlets of the spinal nerves exit the cord horizontally in the cervical region, but at lower levels of the cord they descend to their intervertebral foramen of exit, creating the cauda equina. There are 31 segments of the cord and 31 pairs of spinal nerves (one pair off each segment). Spinal nerves C1 thru C7 exit above the vertebra of the same number. C8 exits below vertebra C7. T1 thru coccyeal 1 exit below the vertebra of the same number. Cervical Spinal Cord

Dorsal rootlets emerge from the dorsolateral sulcus Dural sac Dorsal median opened sulcus (dura mater)

Arachnoid membrane

Ventral median fissure w ant. spinal artery

Posterior spinal Ventral horn is enlarged arteries anastamose due to origin of nerves to on the dorsal surface upper extremity of the cord Cervical enlargement Thoracic Spinal Cord Anterior spinal artery in ventral median fissure

Dura reflected

Lateral horn

Denticulate ligaments (surface pia penetrates archnoid to Ventral median attach to dura, fissure anchoring the cord laterally The thoracic cord is more cylindrical. It has thin H- shaped gray matter, since it only innervates intercostal and axial muscles. Lumbosacral Lumbar & Sacral Spinal Cord enlargement

Conus medullaris

Spinal cord ends at vertebral level L2

Filum terminale Enlarged ventral horn Lumbar due to origin of nerves to the lower extremity

The dorsal and Roots of ventral nerve cauda rootlets of lower equina cord segment make up to cauda equina. Sacral