Spinal Nerve Lecture Notes PDF

(007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 A. GANGLIA / GANGLION OUTLINE...

(007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 A. GANGLIA / GANGLION OUTLINE  Ovoid structure containing neuronal cell bodies (with their I. SPINAL NERVE: INTRO AND DISC HERNIATION dendrites), glial cells, supported by connective tissues. A. Ganglia  Relay stations to transmit impulses (sensory and B. Nerves autonomic) C. Neurodegeneration  Ganglia - group of nerve cell bodies supported by connective tissue found in the PNS. Whereas Nuclei – group of nerve cells D. Gross anatomy without connective tissue found in the CNS. II. RAMI, CERVICAL AND BRACHIAL PLEXUS  In CNS nuclei and tracts is not surrounded by connective III. TERMINAL BRANCHED OF THE BRACHIAL tissue unlike on the ganglia of PNS. PLEXUS IV. LUMBAR AND SACRAL PLEXUS V. DERMATOMES VS. MYOTOMES I. SPINAL NERVE: INTRO AND DISC HERNIATION  Cranial nerve sensory ganglia - Eg.: Trigeminal ganglia(Semilunar Ganglion)  Part of the Nervous system that consists of nerves (Cranial and Spinal) and their ganglia outside of the Brain and Spinal Cord. 2 types of ganglia  Main components: 1. Sensory ganglia - Ganglia - Nerves (Cranial/Spinal/Peripheral) - Dorsal root ganglia is made up of pseudounipolar - Nerve endings sensory neurons - Unipolar/pseudounipolar cell bodies enveloped by cuboidal cells o Cranial ganglia (e.g. Trigeminal) o Spinal ganglia (Dorsal Root) PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 these transmitters Is probably to modulate the effects of the primary transmitter. Autonomic ganglia - They are referred to as posterior root ganglia 2. Autonomic ganglia - Postganglionic autonomic nerves o Multipolar neurons enveloped by satellite cells (Capsular Cells) o Some are Intramural (within certain organs)  Sympathetic/parasympathetic ganglia o Found on the thoracic and upper lumbar segment of the spinal cord o Connected to the spinal nerve by Rami communicantes o The nerve endings in the autonomic afferent component may not be activated by such sensations as heat or touch but rather by stretch or lack of oxygen. o Postganglionic nerve endings: The postganglionic fibers terminate on the effector cells without special discrete endings. The axons run between the gland cells and the smooth and cardiac muscle fibers and lose their covering of Schwann cells. At sites where transmission occurs, clusters of vesicles are present within the axoplasm. The site on the axon may Ile at some distance from the effector cell; thus, the transmission time may be slow at these endings. The diffusion of the transmitter through the large B. NERVES extracellular distance also permits a given nerve to have an action on a large number of effector  Cranial Nerves cells. - Purely sensory o Parasympathetic postganglionic nerve endings - Purely motor liberate ACh as their transmitter substance - Mixed motor and sensory (Sensorimotor) o Most sympathetic postganglionic nerve endings  Spinal/ Peripheral Nerves liberate norepinephrine as their transmitter - Bundles of nerve fibres (axons) outside the CNS. substance. In addltlon, some sympathetic (once the axons emerges outside the CNS, they postganglionlc nerve endings, particularly those become the Peripheral nerves) that end on cells of sweat glands and the blood vessels in skeletal muscle, release ACh, which - Surrounded by connective tissue; Tracts do not binds with muscarinic receptors on the have connective tissue postsynaptic membrane. - Carries both sensory and motor fibres o All neurons that release Ach at their endings are (Sensorimotor) called cholinergic (work like Ach). o Sympathetic endings that use norepinephrine are  Nerve fibres called adrenergic endings. - Axons enveloped by sheaths of connective tissue. o Sympathetic and parasympathetic postganglionic - Grouped together constitute the nerve. neurons have been shown to liberate substances - Types: other than ACh or norepinephrine at their o Myelinated endings; these include adenosine triphosphate o Unmyelinated (ATP), neuropeptide Y, and substance P. These substances may be released alone or from  neurons that release ACh or norepinephrine; they have their own specific receptors. The function of PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020  Myelinated fibers  - A single Schwann cell wrap around a single axon (Oligodendrocytes, Analogue of Schwann cells in CNS wrap around 60 axons ) Non-myelinated vs myelinated nerve fiber - Enveloped by myelin sheath forming Nodes of Ranvier - Less energy consumed - Corticospinal tract / Motor nerve fibers (More than 1 um - larger axons ) - Myelin sheaths begin to form before birth and during the first year postnatally - Incisures of Schmidt-Lanterman – seen on longitudinal section and represent area where the dork major dense lines in not formed as a result of the localized persistence of Schwann cell cytoplasm. - Has a faster conduction (Saltatory conduction)  Unmyelinated fibers - A single schwann cell envelopes several axons - Several Fibers are enveloped within single clefts of schwann cells. - More energy consumed - Autonomic NS fibers ( Smaller axons ) - In CNS, nonmyelinated nerve fibers run small groups and are not particularly related to oligodenrocytes.  Unmyelinated fibers - A single schwann cell envelopes several axons - Several Fibers are enveloped within single clefts of schwann cells. - More energy consumed - Autonomic NS fibers ( Smaller axons ) - In CNS, nonmyelinated nerve fibers run small groups and are not particularly related to oligodenrocytes. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Demyelinating diseases  Multiple sclerosis – confined to the CNS, a breach in the integrity of the blood-brain barrier (p171)  Encephalomyelitis – immune-mediated inflammatory demyelinating condition that predominately affects the white matter. Associated with polyfocal neurologic deficits and is self- limiting (Medscape)  Neuromyelitis optica  Transverse myelitis- Inflammation of spinal cord resulting to demyelination. (WikiMed)  Guillain Barre syndrome- manifest as an acute inflammatory polyradiculoneuropathy with resultant weakness and diminished reflexes (Medscape)  Central pontine myelinosis- complication of severe and prolonged hyponatremia. Noninflammatory that centered within the pons. (Medscape)  Leukodystrophy- imperfect growth or development of the myelin shealth. (WikiMed) Multiple sclerosis – Autoimmune Clinical correlation  Demyelination- the destructive removal of myelin, an insulating protective sheath.  When axons become demyelinated, they transmit the nerve impulses 10 times slower than normal myelinated ones and, in some cases, they stop transmitting action potentials altogether.  There are a number of clinical diseases associated with the breakdown and destruction of the myelin sheath surrounding brain, spinal cord or peripheral nerve axons  Everything slows down when the myelin sheath is removed The peripheral nerve  Peripheral nerves are composed of bundles of nerve fibers. In their course, peripheral nerves sometimes divide into branches that join neighboring peripheral nerves. If this occurs frequently, a network of nerves, called a nerve plexus forms.  Note that the formation of a nerve plexus allows individual nerve fibers to pass from one peripheral nerve to another, and in most instances, branching of nerve ftben does not take place. A plexus thus permits a redistribution of the nerve fibers within the different peripheral nerves.  At the root of the limbs, the anterior rami of the spinal nerves form complicated plexuses. The cervical and PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 brachial plexuses are at the root of the upper limbs and the - Dense collagenous connective tissue with thick elastic lumbar and sacral plexuses are at the root of the lower fiber limbs. Cutaneous nerves, as they approach their final - Prevent damage byoverstretching destination, commonly form flne plexuses that again permit - enveloped the whole nerve a rearrangement of nerve fibers before they reach their  Perineurium terminal sensory endings. The autonomic nervous system - Dense connective tissue surrounding a fascicle of also possesses numerous nerve plexuses that consist of axons/fibers preganglionic and postganglionic nerve fibers and ganglia. - Layers of epitheloids - Isolates neural environment (Blood-Nerve Barrier) - enveloped each fascicle; blood vessel is located in between the fascicle  Endoneurium - Loose connective tissue surrounding individual axons - Regulation of microenvironment of nerve fiber - envelopes individual fiber Note: Both Motor and Sensory Fibers will pass through the same nerve but not on different Axons Peripheral Nerve Tissue Covering  Epineurium Histology (H & E Stain) - Outermost covering, continuous with the Dura mater PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 C. NEURODEGENERATION  Regeneration of CNS nerve fibers (tracts of Axon) is NOT POSSIBLE following an injury because: - Axons in the CNS do not regenerate following injury. In part, this is due to the fact that CNS myelin contains several proteins that inhibit axonal regeneration. (That is why in surgery, it is not possible to reattached CNS nerve fibers) - Absence of Endoneurium - Oligodendrocytes do not proliferate in response to axonal injury - Astrocytes deposit scar tissue (plaque) preventing cell growth. - Absence of neurilemma - The spinal cord cannot be reattached  Reattachment: - If extremities are severed it is possible to reattach it but first reattach the blood vessel before nerves. However perfect regeneration is not ensured. o It has connective tissue that can be sutured  Spinal nerves are named according to the spinal cord together which allow the reattachment segment from which they originate - 8 CERVICAL  Axonal regeneration is POSSIBLE in PNS - 12 THORACIC - 5 LUMBAR - Presence of endoneurium - 5 SACRAL - Myelin sheath provides a tract along which regrowth - 1 COCCYGEAL occurs - Presence of Neurilemma - Perfect regeneration is not ensured. - The presence of supporting connective tissue makes PNS nerve fibers possible for suturing (Read on Neuronal response to injury Chapter 3). D. GROSS ANATOMY: SPINAL NERVES  Part of the peripheral nervous system - 31 pairs attach through dorsal and ventral nerve roots - Each spinal nerve is connected to the spinal cord by the anterior and posterior root Intervertebral foramina - Opening where the spinal nerves emerge. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Cervical spinal nerves  8 cervical spinal nerve= 7 cervical vertebrae (bone)  Spinal cord segments are superior to where their corresponding spinal nerves emerge through intervertebral foramina  Cervical spinal nerves exit into the foramina from above the respective vertebra - E.g., Spinal nerve that emerges at C1C2 intervertebral foramina = C2 spinal nerve - C3C4 vertebrae: C4 spinal nerve - Clinically, for example when referring to disc impingement (both levels of vertebra mentioned) - e.g., C6-7 disc herniation would impinge on C7 spinal nerve - Symptoms usually include which level. Cauda equina 7 cervical vertebrae (Bone):  Collection of pairs of spinal nerves/ nerve roots at inferior end of vertebral canal  C1-C7 - L2-L5  Cervical - S1-S5  vertebrae - Coccygeal Nerve - Arise from lumbar enlargement and conus 8 cervical spinal nerve: medullaris - C1-C8 - Spinal Nerves (emerging from corresponding intervertebral foramina) Cervical nerves - There is a discrepancy between the number of the cervical nerve (8) to the number of cervical vertebrae (7) - The cervical nerve is named after that specific cervical vertebra below that cervical nerve Laminectomy - Removal of the lamina of the vertebra to access the spinal cord PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Herniated disc axial view - A herniated disc in axial view goes to lateral side and the disc protrudes between the vertebra and impeached the nerve. Disc herniation - A herniated disc refers to the bulging that emerges from the vertebral canal. - Symptoms of herniation depend on what function of the affected level of the spinal cord. - Several factors may impinge spinal nerves such as bone spur on the facet, or herniated disc Far lateral disc herniation - The nerve that will impinge is the nerve that emerges on the intervertebral foramina. - *Normal intervertebral disc in MRI is white which means hydrated or having water content. - *Spinal canal in MRI is also white due to CSF - *Disc is made of nucleus pospolus and annulus fibrosus - *Paracentral disc herniation has associated spinal stenosis. - *Discectomy is the removal of the intervertebral disc PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Thoracic/lumbar/ sacral spinal nerve - The remaining spinal nerve pairs Thoracic/Lumbar/Sacral emerge from the spinal cord below the same- numbered vertebra - EG: o Spinal nerve emerging between L4L5 = L4 Spinal nerve o Spinal nerve emerging between T3T4 = T3 spinal nerve Note: Most lumbar disc herniations are paracentral/posterolateral, thus the root that gets compressed is actually the root that exits the foramen below the herniated disc. Thus, in a posterolateral/Paracentral herniated disc at L4L5 will compress the L5 spinal nerve. L5S1 posterolateral disc herniation will compress the SI spinal nerve. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020  Thoracic herniated discs are rare  Bone spurs or tumors in the neural foramina affect nerve roots the as the lumbar region.  Lumbar nerves exit inferior to their associated vertebra.  The IV discs are named for the supra- and infra-adjacent vertebrae.  Most IV disc herniations occur; o L4-L5 and L5-S1 o Posteriorly Spine-nerve impingement  Cervical nerves exit superior to their associated vertebra  IV discs are named for the supra and infra-adjacent vertebrae  Cervical IV disc herniations impinge the nerve in the neural foramen. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Lumbar Vertebrae II. RAMIS & CERVICAL AND BRACHIAL PLEXUS Spinal nerves  Dorsal roots - sensory fibers arising from cell bodies in the dorsal horn of the spinal cord  Presence of Dorsal root ganglia (Cell bodies of Unipolar/pseudo unipolar neurons)  Ventral roots - motor fibers arising from cell bodies in the anterior gray column of spinal cord Just outside foraminaas spinal nerve Emerges, divides into:  Dorsal rami serve the muscles and skin of the posterior trunk - Back, from neck to sacrum, innervated in a neatly segmented pattern: horizontal strip at same level as it emerges from spinal cord  Ventral rami serve the muscles and skin of the lateral and anterior trunk - In thorax only, a simple segmented pattern as intercostal nerves Supply the limbs/extremities by forming plexuses  Both dorsal and ventral Ramus /Rami carries sensory and motor fibers  VENTRAL RAMI in the THORAX form the intercostal nerves and do not form plexuses PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Spinal nerve divide to the dorsal and ventral ramus  Dorsal ramus – innervates the muscle and skin of the back and trunk  Ventral ramus- innervate the muscle and skin of the anterior portion Rami Communicantes  Supply the visceral motor information towards the sympathetic chain ganglion  *Nerve plexus is protective in such a way that when one nerve is traumatizing or destroyed the other member of that plexus takes over that function.  *Spinal nerve injury between C3-C5 will result in respiratory arrest which causes you to have a hard time to breath; however, other mechanisms will take over to the function of the diaphragm like abdominal muscles but it is worn out fast Nerve plexuses  Networks of successive ventral rami of cervical, lumbar, sacral spinal nerves that exchange fibers (crisscross& redistribute)  Protective  Mainly innervate the limbs  Thoracis ventral rami do not form nerve plexuses (except T1 or sometimes T2 which may be part of the brachial plexus) PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Plexuses  Cervical  Brachial  Lumbar  Sacral - Corresponds to the spinal cord bulges - No thoracic plexus Cervical Plexus  C1-C4  Innervates the muscles and skin of the neck and shoulder  Important Nerve to consider  Phrenic Nerve (C3, C4, C5) (DIAPHRAM) Cervical spinal cord injuries C3 – C5 and Above = Respiratory arrest  The abdominal muscles can take over the function of the diaphragm in breathing but it will take only a little time. Abdominal muscles will get exhausted Phrenic Nerve (C3C4C5) -Sole motor supply to the Diaphragm (Primary muscle for breathing PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Division – (anterior and posterior division)  Don’t have any branches  Anterior division -associated with the muscle of the anterior compartment  Posterior division- associated with the muscle of posterior compartment Cord- (later, posterior and medial cord)  Lateral and medial cord formed from the anterior division  Posterior cord formed from the posterior division Cord terminates to 5 terminal nerves: MY AUNTY RAPED MY UNCLE M-musculocutaneous (from latera cord) A-axillary (from the posterior cord) R-radial (from the posterior cord) M-median (from the lateral and median cord) U-ulnar (from the median cord) Lateral pectoral nerve  innervates pectoralis major muscle (Emerges from the lateral cord) III. TERMINAL BRANCHED OF THE BRACHIAL Medial pectoral nerve  the most proximal nerve in the median cord PLEXUS Posterior cord terminal nerve: Terminal branches ULTRA U- Upper (superior) subscapular – innervates the s ubscapularis L- Lower (inferior) subscapular – innervates subscapularis and teres major T-Thoracodorsal – innervates latissimus dorsi muscle R-radial A-Axillary Terminal Brachial plexus ROOT  Dorsal scapular nerve- the nerve in the root of brachial plexus (C5 spinal nerve) that innervates the rhomboid muscle  Long thoracic nerve- runs from the root of C5-C7 spinal nerve which innervates the serratus muscle Trunk (superior, middle, and inferior trunk)  Nerve to subclavius – from superior trunks that innervates subclavius muscle  Resides in the cervicoaxillary canal over the first rib  Suprascapular nerve – from superior trunk innervates  Formed by the ventral ramus of the lower 4 cervical nerves supraspinatus and infraspinatus (C5-C8) and the first Thoracic Nerve (T1), sometimes T2 PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020  Supplies afferent (sensory) and efferent (motor) nerve fiber to chest, shoulder arm and hand  Except: Trapezius muscle, Accessory nerve (CN 11) - Skin near axilla, intercostobrachial nerve- cutaneous branches of intercostal nerve Brachial plexus  separated into roots, trunks, division, and cord (Terminal Branches and its Innervation (summary) Table see.Appendix 1) Median nerve – the union of lateral and medial cord)  Median nerve formed anteriorly to the axillary artery  Innervate palm muscle; thenar muscle such as abductor pollicis brevis; flexor pollicis brevis; opponens pollicis; 2 lumbricals Median nerve -sensory to the lateral 3 ½ digits Ulnar nerve - sensory to medial 1 ½ digit Radial nerve- sensory to the dorsal lateral 2/3 of the hand PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Carpal Tunnel Syndrome (median nerve compression)  Femoral nerves also innervates skin on anterior thigh (including quads) and medial leg  Median entrapment neuropathy that causes paresthesia,  from anterior rami of L1-L4 and received some fiber from pain, numbness, and other symptoms T12 in the distribution of the median nerve due to its  6 nerves compression at the wrist in the carpal tunnel.  Lumbar plexus forms inside psoas major muscle  Compression of the transverse carpal ligament  Cause paresthesia to the sensory 3 ½ digits that are supplied by the median nerve  Median nerve compression 2 nerves from 1 root  Iliohypogastric and ilioinguinal emerge from 1st lumbar root  *Iliohypogastric is superior to ilioinguinal since the gastric (stomach) region is above the inguinal region 2 nerves from 2 roots  Genitofemoral arise from anterior rami of L1 and L2  Lateral femoral cutaneous arise from anterior rami of L2 IV. LUMBAR AND SACRAL PLEXUS and L3 2 nerves from 3 roots  Obturator and femoral nerve originate from L2 to L4 root Lumbar plexus  Obturator nerve- innervates the muscle of the major compartment of the thigh  L1-L4 and may also include the subcostal nerve (T12)  Femoral nerves- innervate the muscle anterior  Lies within the psoas major muscle compartment o the thigh  Innervates anterior and medial muscles of thigh through femoral and obturator nerves respectively (both have Accessory obturator nerve arise from L3 and L4 this nerve is not always present contributions from L2L3L4 spinal nerves)  *Femoral nerve has two muscular branches nerve for psoas muscle and iliacus muscle PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020  Supply the muscle of the pelvis and lower limb  Located at posterior pelvic wall anterior to piriformis muscle  L4 and L5 nerve combine to from lumbosacral trunk which contribute to sacral plexus  Lumbosacral trunk descends in the pelvis to meet the sacral Roots as they emerge from the spinal cord.  Sacral plexus begins at the anterior fiber of s1 to s4  Sacral fibers emerge by anterior sacral foramina  The sacral plexus is formed on the anterior surface of the piriformis muscle Five major peripheral nerve under the sacral plexus  Superior and inferior gluteal nerves  Sciatic nerve  Posterior femoral cutaneous nerve  Pudendal nerve *Sacral plexus nerves descend at the posterior pelvic wall and have three possible courses. *The first of which is to leave the pelvis far the greater sciatic foramen and enter the gluteal region of the lower limb, either above or below the piriformis muscle. *The second course is to remain within the pelvis and to innervates the pelvic muscle organs and perineum. *The third course is to leave at the greater sciatic foramen loop around the sacred spinous ligament. And we enter for the Lesser sciatic foramen to supply lateral pelvic structures and perineal structures. Sacral plexus  L4-S4  Supplies muscles and skin of posterior thigh and almost all the leg  Main branch is the large sciatic nerve, which consist of: - Tibial nerve- to most of hamstring, calf and sole - Common fibular nerve- to muscles of anterior and lateral leg and skin  Other branches supply pelvic girdle (gluteus muscle) and perineum (pudendal nerve) PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020  Leave the pelvis via the greater sciatic foramen to enter the gluteal region  Motor- innervates the skeletal muscles in the perineum the external urethral sphincter the external anal sphincter  Sensor- innervates the penis and the clitoris and most of the skin of the perineum Other branches: *Perforating cutaneous nerve  Originates from S2 and S3  Innervates the skin of the gluteal fold.  Perforates the sacred tuberous ligament to provide its cutaneous innervation *Pelvic splanchnic nerves  Innervate the abdominal viscera *Nerve to piriformis  Formed from S2 and occasionally from S1 innervates the piriformis muscle directly *Nerve to obturator internus  Originates from L5 to S2  Exits the pelvis by the greater sciatic foramen  Directly innervate the obturator internus muscle and also the superior gemellus *Nerve to quadratus femoris  Originates from L4 to S1 Superior gluteal nerve  Leaves the pelvis by the greater sciatic foramen inferior to  Originates from nerve Roots L4 L5 and S1. the piriformis muscle  Leaves the pelvis via the greater sciatic foramen entering  Innervates the quadratus femoris as well as the inferior the gluteal region superiorly to the piriformis muscle gemellus muscle.  Innervates the gluteus Minimus and medius, tensor fasciae lata Rough summary of each Spinal level of function Inferior gluteal nerve  Originates from spinal nerve Roots L5 S1 and S2  Leaves the pelvis far the greater sciatic foramen entering the gluteal region inferior lie to the piriformis muscle.  Innervates the gluteus maximus muscle. Sciatic nerve  The largest nerve of the body  Derived from five nerve roots from L4 to S3  Formed on the anterior aspect of the piriformis muscle and it exits the pelvis for the greater sciatic foramen inferior to the piriformis in terms of motor function the tibial portion of the sciatic nerve innervates all of the muscles in the posterior compartment of the thigh except for the short head of the biceps femoris  Two components - The common fibular component is formed from the dorsal divisions of L4 to S2 - The tibial component is formed from the ventral divisions of L4 to S3. Posterior femoral cutaneous nerve  Originates from spinal nerve Roots S1 S2 and S3  Leaves the pelvis by the greater sciatic foramen entering the gluteal region inferior  This nerve has an only sensory function  Innervates the skin on the posterior surface of the thigh and the leg and it also innervates the skin of the penis. Pudendal nerve  Originates from nerve roots S2 to S4. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 V. DERMATOMES VS. MYOTOMES Dermatome  Sensory innervation of the skin from a single spinal nerve  Gk. skin Gk. section, volume of  Area of skin innervated by the cutaneous branches from a single spinal nerve  Reveal sites of damage/injury to the spinal nerves or the spinal cord  Part of somite which migrates out and forms the dermis of the skin  Also, have dorsal root ganglion cells which is a sensation from the developing dermis to their associated spinal cord level.  The area of skin supplied by a single spinal nerve and, therefore, a single segment of the spinal cord is called a dermatome. On the trunk, dermatomes extend round the body from the posterior to the anterior median plane. Adjacent dermatomes overlap considerably, so to produce a region of complete anesthesia, at least three contiguous spinal nerves have to be sectioned.  In the limbs, the arrangement of the dermatomes is more complicated because of the embryologic rotation of the limbs as they grow out from the trunk. Nerve Designation C- cervical T- thoracic L-lumbar S-sacral PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Dermatome: 1. Area of skin innervated by a single spinal cord level 2. Part of the somite that gives rise to the dermis PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 3. Dermatome has segmental organization  Due to formation of skin, dermatome maps vary PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Where do you test each dermatome? L5 Dorsum of the foot over the third metatarsal NERVES LOCATION IMAGE phalangeal joint C5 Lateral side of the elbow S1 Lateral aspect of the C6 Dorsal surface of the calcaneus (heel) proximal phalanx of the thumb C7 Dorsal surface of the proximal phalanx of the middle finger S2 Midpoint of the popliteal fossa C8 Dorsal surface of the proximal phalanx of the little finger S4-S5 Perineal region just beside the opening of the sphincter T1 Medial side of the elbow T4 Midclavicular line at the level of the nipple T10 Midclavicular line at the level of the umbilicus L3 Medial femoral condyle above the knee L4 Over the medial malleolus PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Variations in the dermatome maps: Myotomes  Anatomist  Gk. a volume of muscles  PT/OT  A group of muscles innervated by single of spinal  Family medicine cord or spinal cord level  Neurolgy  Part of the somite that gives rise to the skeletal  Sports medicine muscle that migrates out to the body  PM and R  Skeletal muscle migrates out where at every level there is an associated spinal cord level that has a motor neuron that sends its axon out to innervate those groups that group of muscles associated with that segmental level.  A myotome is the group of muscles that a single spinal nerve innervates. In vertebrate embryonic development, a myotome is the part of a somite that develops into the muscles. Myotome level discrepancies E.g.  *Supraspinatus muscle has a big contribution from C5 and a little from C6. While the deltoid has a big contribution from C5 and C6 and both of those muscles are the primary abductors of the glenohumeral joint, but then the biceps are PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 also having big contributions from C5 and C6. Technically the test for the C5 and C6 myotome is a combination of the abduction of the shoulder and flexion of the elbow.  Migrating myotomes result in overlapping, where some muscle often has in the upper and the lower limbs more than one level contributing spinal cord that contributes on its Innervation Myotome  Testing a movement enables you to see if the associated spinal cord/ nerve level is intact. PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Upper Limb Myotome and Lower Limb Myotome Upper limb myotome PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Lower Limb myotome PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 VI. TEST YOURSELF 11. Lumbar plexus that originates from L1 only a. Obturator 1. Dermatomes is the area of skin innervated by the motor b. Femoral fibers of a spinal nerve c. Genitofemoral a. True d. Iliohypogastric & ilioinguinal b. False 2. Where would you test for the C7 dermatome? a. Thumb b. Little finger Anskey: 1. B c. Middle finger 2. C d. Ring finger 3. C 4. A 3. All are nerves under the lumbar plexus except 5. C a. Illiohypogstric nerve 6. B 7. B b. Ilioinguinal nerve 8. D c. Posterior femoral cutaneous nerve 9. Phrenic nerve d. Lateral femoral cutaneous nerve 10. C5 11. D 4. Sacral plexus originates from S2-S4 a) Pudendal nerve b) Sciatic nerve c) Superior gluteal nerve d) Inferior gluteal nerve VII. REFERENCES 5. The spinal nerve affected in paracentral herniation Snell’s Clinical Neuroanatomy 8th ed., Chapter 01 pages 12-20 between L3 and L4 Chapter 03 pages 71-83, 93-119 a. L2 b. L3 c. L4 d. L5 6. The spinal nerve affected in far-central herniation between L3 and L4 vertebra a. L2 b. L3 c. L4 d. L5 7. The herniation between C7 and T1 vertebra will affect what spinal nerves a. C7 b. C8 c. T1 d. T2 8. What nerve innervates the rhomboid muscle a. Long thoracic nerve b. Nerve to subclavius nerve c. Suprascapular nerve d. Dorsoscapular nerve 9. The nerve that provides primary motor supply to the diaphragm is the ______. 10. Myotome for shoulder adduction a. C5 b. C4 c. C3 d. C8 PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 VIII. APPENDIX Appendix 1. Terminal Brances and its innervation PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Appendix 2. Myotome level Discrepancies Appendix 3. Myotome level Discrepancies (cont.) PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,  (007) THE SPINAL NERVE - LEC DR. ALLAN T. VIADO,MD,FAFNi, FPCS I 11/03/2020 Appendix 4. ASIA (American Spinal Injury association) SCORE PREPARED AND EDITED BY: KANAN S., KOLIPAKA E., PRINCE J., KUMAR R., MONCADA R., MOTIC G., MUNAR R.,