Spinal Cord and Brain Stem Prof. K. Sivapalan

Spinal Cord and Brain Stem Gross Structure The upper end continues as the medulla oblongata at the upper border of the C1 vertebra 31 pairs of spinal nerves come out of spinal cord. Cervical and lumbar enlargements to accommodate neurons that innervate the limbs 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Nerve Roots Anterior and posterior nerve roots. Each root is formed by aggregation of several rootlets that arise over a certain length of the cord Rootlets of one root arise from one spinal segment The dorsal rootlets arise along the postero-lateral salcus The dorsal root has the dorsal root ganglion. The two roots meet to form the spinal nerve that emerges through the intervertebral foramen. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Length of the Cord The spinal cord is equal to the vertebral canal during early fetal life. The vertebra out grow the spinal cord and the lower end is at L3 at birth The lower end of the adult cord is at the lower border of the L1± 1 vertebra. The spinal nerves travel in the vertebral canal until they reach the appropriate intervertebral foramina. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Conus Medullaris The lower end is called conus medullaris. It continues as fibrous cord called filum terminale up to the sacrum. The spinal nerves beyond the end of the spinal cord form the cauda equina 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Structure of the Cord Butterfly shaped [H shaped] gray matter surrounded by white matter. White matter is in three funiculi [columns] on either side: Anterior funiculus between anterior median fissure and anterior root Lateral funiculus between anterior and posterior roots Posterior funiculus between the posterior root and the posterior median septum 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem The Gray Matter Central gray with a minute central canal Anterior [motor] and posterior [sensory] horns on either side A lateral gray horn [autonomic- dorsal sensory and ventral motor] in the spinal segments from T1 to L2 , S2-S4. 7/28/2019 Spinal Cord and Brain Stem

Communication Between Both Sides Gray commissure anterior to the central canal Anterior white commisure deep to the anterior median fissure 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem The spinal cord continues as the brain stem in the base of the skull. The arrangement of gray in the centre and white matter around in the spinal cord is disturbed in the brain stem because of the flexures and development . The ascending, descending and transverse tracts divide the gray into collection of cells called nuclei. In addition to recognizable nuclei, neurons are disbursed through out the brainstem performing autonomic and other functions. These neurons are named reticular formation collectively 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Medulla Transition of spinal cord to medulla is not abrupt at the upper border of atlas but over a certain distance. It is narrow [closed- around central canal] below and widens above [open- under fourth ventricle]. 3 cm long and 2 cm at the upper end The surface has longitudinal fissures and sulci that divide it into regions. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Anterior aspect Anterior median fissure and posterior median sulcus are continuations from spinal cord. Antero lateral sulcus lies in line with ventral roots of the spinal nerves The rootlets of the hypoglossal nerve [12] emerge from this sulcus 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Anterior aspect ctd The area between anterior median fissure and anterior medial sulcus is occupied by an elevation called the pyramid Fibers in pyramid decussate obliterating the fissure. The region between anterolateral and posterolateral sulci has a prominent, oval about 1.3 cm long swelling named olive Inferior olivery nucleus lies under this 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Posterior Aspect Posterolateral sulcus lies in line with dorsal roots and ninth, tenth and eleventh nerves emerge from this. The area between the posterior median sulcus and posterior lateral sulcus two rounded elevations called gracile and cuneate tubercles are seen. They contain nucleus gracilis and nucleus cuneatus under them. The fourth ventricle continues below as the central canal. Connects to cerebellum by the inferior cerebellar peduncle. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Pons The junction of pons and medulla is marked by a groove through which sixth, seventh and eighth nerves emerge. Trigerminal nerve [5] emerges from the anterior surface. Nerve fibers run transversely and form the middle cerebellar peduncle laterally. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Pons ctd. Connects to cerebellum by the middle cerebellar peduncle The lateral aperture of the fourth ventricle lies on either side of the lower pons near the cerebello-pontine angle Posterior aspect forms the floor of fourth ventricle. 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Mid Brain Anteriorly two large bundles of fibers are seen on either side of the midline. These are named the crura of the midbrain [cerebral peduncles] The crura are separated by a deep fissure, diverging to enter the cerebral hemispheres. The occulomotor nerve emerges from the medial aspect of the crus. Fourth nerve emerges from the dorsal surface 7/28/2019 Spinal Cord and Brain Stem

Spinal Cord and Brain Stem Mid Brain ctd. Midbrain is continuous with cerebral hemisphers above The posterior aspect is marked by two pairs of rounded swellings known as superior and inferior colliculi. The aqueduct continues below as the fourth ventricle Connects to cerebellum by the superior cerebellar peduncle. 7/28/2019 Spinal Cord and Brain Stem