Neuroscience 1A LC 16 Spinal Cord PDF

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC 16 SPINAL CORD COLLEGE OF MEDICINE, BATCH 2026 Transcribers...

UNIVERSITY OF NORTHERN PHILIPPINES NEUROSCIENCE 1A LC 16 SPINAL CORD COLLEGE OF MEDICINE, BATCH 2026 Transcribers: Quilana, Reyes, Rivera, Rodriguez, Rosalin Dr. Allan Viado | Dec. 2022 Editors: Quilana, Reyes, Rivera, Rodriguez, Rosalin LECTURE OUTLINE I. Introduction II: Internal Anatomy III: Spinal Pathways (Overview) IV. Ascending Sensory Pathways V: Proprioception VI: Descending Motor Pathways VII: Clinical Applications VIII. Supplemental Information I. INTRODUCTION A. FORAMEN MAGNUM Figure 1. Nervous System - Only true effective opening in the intact skull - Marks the opening or start of the spinal cord - Herniation syndrome- occurs when a tumor or hematoma Figure 2 and 3. Location of the Foramen Magnum in the Skull or infarct inside the skull produces pressure that moves Inferior View brain tissue Once the medulla oblangata exits the foramen magnum it becomes the spinal cord Page 1 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado A. SPINAL CORD DEVELOPMENT Denticulate Ligaments - Lateral shelves of pia mater anchoring to dura FETAL: 3rd month ends at coccyx - Function: holds the spinal cord in place BIRTH: ends at L3 ADULT: between L1-L2 during childhood B. THE SPINAL CORD GROSS ANATOMY Conus medullaris - end of spinal cord - This tapers into Filum Terminale of connective tissue, tethered to coccyx. Cauda equina - arise from the lumbar enlargement and Conus medullaris - “horse tail” (L. word meaning a bundle of spinal nerves) - L2-L5 nerve pairs - S1-S5 nerve pairs - Coccygeal nerve Figure 4,5,6 and 7. Spinal Cord and Associated Structures Looks like a cone Note that the spinal cord is protected by the vertebral canal/ spine; It doesn’t encompass the whole spinal canal; it ends at the level of Made up of several spinal nerve L1L2 called conus medullaris (L2-L5; S1-S5; coccygeal nerve) It lies within the vertebral canal and is protected by three surrounding fibrous membranes, the meninges. It is cushioned against trauma by the cerebrospinal fluid and is held in position by the denticulate ligaments on each side and the filum terminale inferiorly Page 2 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado SPINAL CORD PLEXUSES - Foramen magnum to Lumbar level L1L2 (Conus Medullaris) - collection of spinal nerves - Runs through the vertebral canal of the vertebral/spinal o Neck/ shoulder/ upper limbs innervation 1. Cervical column (protects the spinal cord) 2. Brachial o Lower limb innervation 1. Lumbar 2. Sacral → Note: No thoracic plexus (because there is no extremity in the thorax) o Functions: 1. Two-way conduction (Motor and Sensory) pathway between body and the brain ▪ Motor and sensory fibers run through different tracts - Ascending tracts (sensory) - Descending tracts (motor) 2. Sensory and motor innervation of entire body inferior to the head through the spinal nerves arising from Figure 8. Spinal Cordand Associated Structures different segments of the spinal cord. ▪ Both motor and sensory fibers run through the - Foramen Magnum to Conus Medullaris same spinal/ peripheral nerve but on different - 2 enlargement/bulges due to greater number of fibers/axons axons/ different fibers. o Cervical – Upper extremity innervation 3. Major center for reflexes: reflex is an unconscious - C4 – T1 information that reaches the spinal cord only and - Corresponds to brachial plexus does not ascend to high centers/ cerebral cortex Serves as the motor and sensory to the upper extremity ▪ Eg: Patellar reflex, biceps reflex, abdominal o Lumbar – Lower extremity innervation reflex, cremasteric reflex, bulbocavernosus - L1 – S3 reflex, etc. - Corresponds to lumbar plexus Serves as the motor and sensory to the lower extremity C. THE SPINAL CORD COVERINGS AND SPACES Three coverings that produce potential spaces in between: o Dura mater – outermost and thickest covering; composed of connective tissue o Arachnoid mater – contains CSF and blood vessels o Pia mater – adherent to spinal cord Intervertebral foramena Figure 10. Cross section of Spinal Cord and Vertebra Figure 9. Spinal Cord Associated Structures and Spinal Nerves - These meninges are continuation of the meninges of the brain (same structural composition) Remember that the dorsal root ganglion is made up of nerve cell bodies called pseudounipolar neuron; it carries sensory information; afferent; towards the SC Ventral root ganglion – efferent; away from the SC Page 3 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Remember to insert needle below L1L2 to avoid hitting the conus medullaris; needle is usually inserted at L3-L4 or L4-L5 SAGITTAL SECTION THROUGH SPINAL CORD o Intervertebral disc o Vertebral body o Dura mater o Extradural or epidural space o Spinal cord o Subdural process o Spinous process Figure 11. Spinal Cord Coverings 7 bone you FOUR (4) POTENTIAL SPACES The following may develop during trauma can feel at o Epidural – between spine (bone) and Dura Mater; also your back called extradural o Subdural – between Dura and Arachnoid Mater o Subarachnoid – between Arachnoid and Pia Mater o Intraparenchymal – within the spinal cord Figure 11. Spinal Cord Sagittal section → The subdural space is not naturally occurring but may develop due to trauma/ pathologic events II. INTERNAL ANATOMY OF THE SPINAL CORD LP (LUMBAR PUNCTURE) = SPINAL TAP - Needle introduced into Subarachnoid space to collect CSF - Lumbar spine needs to be flexed so can go between spinous processes POSTERIOR - Epidural space is external to dura o Anesthestics are often injected into epidural space injection into correct space is vital; mistakes can be lethal ANTERIOR Figure 12. Insertion of Lumbar puncture needle in L4-L5 Figure 14 and 15. Cross section of Spinal Cord Page 4 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado ▪ Anterior (ventral) horns (cell bodies of motor neurons / Somatic Motor Neuron cells) – for skeletal muscle contraction Figure 16. Internal Spinal Cord Figure 16. Internal Spinal Cord o Lateral horns in thoracic and superior lumbar cord (T1 A. GREY AND WHITE MATTER OF THE SPINAL CORD – L2) – contains autonomic (Sympathetic) o Hollow central cavity (“central canal”) is surrounded preganglionic motor neuron cells that innervate the by central gray commissure visceral organs (Heart, Lungs, Stomach, intestines, o Grey matter surrounds central canal made up of etc.) nerve cell bodies and their dendrites ▪ Horner’s Syndrome – damage to the lateral o White matter surrounds grey matter made up of horns ascending and descending tracts of axons Triad of Ptosis (dropping of the o Grey matter is “H” shaped on cross section eye), anhidrosis (inability to o Dorsal Horn of “H”: cell bodies of sensory neurons / sweat), and miosis (constricted interneurons pupil) o Ventral Horn of “H”: cell bodies of motor neurons o Later horn is found only in the thoracolumbar level o Remember that the spinal cord has no cortex unlike the brain Figure 17. Cross section of Spinal Cord o Grey commissure surrounds the central canal ▪ Connects the 2 halves of the spinal cord o Columns of grey matter running the length of the spinal cord ▪ Posterior (dorsal) horns (interneurons / cell Figure 19. Spinal Cord and Associated Nervesand bodies of sensory neurons) Prevertebral Ganglia Page 5 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Remember! A. ASCENDING PATHWAYS Back / Dorsal / Posterior (Horn/Column/Root): pathway for Sensory afferent information to the CNS ASCENDING PATHWAYS: sensory information by multi-neuron Front / Ventral / Anterior (Horn/Column/Root): pathway for chains from body (from each segmental spinal cord level) up to more Motor efferent information away from the CNS rostral regions of CNS (carries afferent sensory information) Dorsal Column Medial Lemniscus Tract/DMLS - Fasciculus cuneatus carries information from the upper half of the body. - Fasciculus gracilis carries information from the lower half of the body. Spinothalamic Tracts (Anterolateral Tract) DENTICULATE - It will reach the Somatosensory Cortex = Conscious LIGAMENT information - Carries the information from the spinal cord to the thalamus (ascending) DORSAL - Anterior Spinothalamic Tract carries information about ROOT light or crude touch - Lateral Spinothalamic Tract carries information on pain and temperature - Have a three-neuron chain (First, second and third order neuron). Spinocerebellar Tracts - (carries information about Proprioception) - Posterior and Anterior Spinocerebellar Tract - unconscious proprioception SPINAL NERVE NOTE: Dorsal column medial lemniscus system and anterolateral system will reach the Somatosensory Cortex so the information that they are relaying are conscious information while Spinocerebellar Tract carry the information only up to the Cerebellum and relay SPINAL unconscious information NERVE B. DESCENDING PATHWAYS Figure 20. Internal Components of Spinal Cord. DESCENDING PATHWAYS: motor instructions from brain to more caudal regions (carries efferent motor information) III. SPINAL PATHWAYS Pyramidal system: pass thru the pyramids of the medulla Corticobulbar – emerge as Cranial Nerves (carries information for the cranial nerves) Pyramidal (Corticospinal) – emerge as Spinal Nerves – Lateral: motor info for limbs (skilled movement) – Anterior: Axial muscles All others are “extrapyramidal” - tracts that do not traverse the pyramids of the medulla - vestibulospinal, rubrospinal, reticulospinal, olivospinal ❖ Most pathways cross (or decussate) at some point. Take note where they decussate. Figure 21. Cross section of the Spinal Cord Showing the Ascending & A lesion of an anterior root will result in paralysis of any muscle Descending tracts that is supplied exclusively by that root and a partial paralysis of Page 6 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado any muscle that is supplied partially by that root. In both cases, worse, and the person may fall) fasciculation and muscle atrophy occur. - hypotonia as the result of loss of proprioceptive information that arises from the muscles and joints Injury to the Ascending Tracts within the Spinal Cord; - loss of tendon reflexes, owing to degeneration of the afferent fiber component of the reflex arc (the knee and Lateral Spinothalamic Tract; ankle tendon jerks are lost early in the disease). - contralateral loss of pain - thermal sensibilities below the level of the lesion Anterior Spinothalamic Tract; C. MAJOR FIBER TRACTS IN WHITE MATTER OF SPINAL CORD - contralateral loss of light touch and pressure sensibilities (ASCENDING AND DESCENDING PATHWAYS) below the level of the lesion. SENSORY MOTOR Fasciculus Gracilis and Fasciculus Cuneatus; - cuts off the supply of information from the muscles and joints to consciousness. - loss of vibration sense below the level of the lesion on the same side. - loss of tactile discrimination on the side of the lesion Treatment of Acute Pain - Drugs such as salicylates can be used to reduce the synthesis of prostaglandin, Local anesthetics, such as procaine, can be used to block nerve conduction in peripheral nerves. Figure 21. Cross section of the Spinal Cord Showing the Ascending & - Narcotic analgesics, such as morphine and codeine, reduce Descending tracts the affective reaction to pain and act on the opiate receptor sites in the cells in the posterior gray column of Figure 22. Cross section of the Spinal Cord Showing the Sensory (Ascending) the spinal cord, as well as other cells in the analgesic & Motor (Descending) Pathways system in the brain Damage to motor tracts: Paralysis / Paresis (depending on the Treatment of Chronic Pain extent of the damage) - New techniques, acupuncture, and electrical stimulation of Damage to sensory tracts: Anesthesia / Paresthesias the skin - Relief of pain can be achieved using placebos in a few patients. IV. ASCENDING SENSORY PATHWAYS - The anticipation of the relief of pain is thought to stimulate the release of endorphins, which inhibit the normal pain ASCENDING PATHWAYS / TRACTS FOR SOMATIC SENSES - Thousands of nerve fibers in each pathway. o Spinocerebellar tract: subconscious proprioception sense Tabes Dorsalis; from skeletal muscles to cerebellum of same side (don’t - stabbing pains in the lower limbs, which may be very cross) severe. -The presentation is always ipsilateral if there is a damage - paresthesia, with numbness in the lower limbs in the cerebellum. - hypersensitivity of skin to touch, heat, and cold o Posterior/Dorsal Column: discriminative or fine touch / - loss of sensation in the skin of parts of the trunk and lower conscious joint position (proprioception) and vibration limbs and loss of awareness that the urinary bladder is full sensation through thalamus to somatosensory cortex - loss of appreciation of posture or passive movements of (cross in medulla) the limbs, especially the legs o Lateral Spinothalamic tract: carries nondiscriminative - loss of deep pain sensation, such as when the muscles are sensations (pain, temperature, pressure, light/crude touch) through the thalamus to the primary forcibly compressed or when the tendon Achilles is somatosensory cortex (cross in spinal cord before compressed between the finger and thumb ascending) - loss of pain sensation in the skin in certain areas of the body, such as the side of the nose or the medial border of the forearm, the thoracic wall between the nipples, or the lateral border of the leg - ataxia of the lower limbs as the result of loss of proprioceptive sensibility (the unsteadiness in gait is compensated to some extent by vision; however, in the dark or if the eyes are closed, the ataxia becomes Page 7 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado ▪ Free nerve endings – pain (Nociceptor) and temperature (Thermoreceptor) ▪ Merkel discs/cells – fine touch ▪ Root hair plexuses – hair follicle receptors, fine touch o Encapsulated ▪ Meissner’s corpuscles – fine touch in hairless skin (palm of the hands and the sole of the foot) ▪ Ruffini’s corpuscles – deep pressure and stretch ▪ Pacinian corpuscles – deep pressure, vibration Visceral (Ex: Abdomen) : pain, nausea, hunger, fullness ▪ Neuromuscular and Neurotendinous spindles (Muscle Spindles) Figure 23. Spinocerebellar, DCML and Spinothalamic Pathway 5 BASIC MODALITIES OF SENSATION o Touch: Fine (discriminative) and Light (crude/nondiscriminative) o Vibration o Joint position sense (Proprioception): conscious (through DMLS pathway) and subconscious (through spinocerebellar tract) o Pain (Pin prick) o Temperature Note: → DCML – Discriminative sensation through large fiber tracts → Spinothalamic (anterolateral) – Non-discriminative through small fiber tracts SENSORY RECEPTORS By location: o Exteroceptors - Sensitive to stimuli arising from outside body - Conscious sensation o Interoceptors - Or visceroreceptors, from internal viscera o Proprioceptors - Monitor degree of stretch in skeletal muscles, tendons, joints and ligaments SENSORY EXTERORECEPTORS Figure 24. Skin Layers Showing Receptor Locations o Unencapsulated Page 8 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado DORSAL (POSTERIOR) COLUMN – MEDIAL LEMNISCUS PATHWAY (DCML) o Posterior Columns - Position - Vibration - Fine touch (Discriminative touch) ANTEROLATERAL SYSTEM o Lateral Spinothalamic Tract - Pain - Temperature - Crude & Light Touch (Non-discriminative touch) NOTE: o Fine touch - Discriminative touch eg: two point discrimination - A sensory modality that allows a subject to sense and Figure 26. Internal Spinal Cord localize touch (at least 5mm distance) o Crude/Light Touch SENSORY AREAS POSTERIOR TO CENTRAL SULCUS - Non-discriminative o Primary somatosensory cortex: postcentral gyrus of parietal - Sensory modality that allows the subject to sense that lobe (allows conscious awareness of sensation and the ability something has touched them, without being able to to localize it: where the sensation is from): Brodmann area localize where they were touched 3, 2, 1 o Somatosensory association area: behind it (understanding of what is being felt: the meaning of it) (Broadmann area 5,7) Figure 25. Dorsal column medial lemniscus and spinothalamic tract NOTE: The Dorsal (posterior) column medial lemniscus tract remains ipsilateral to medulla where it crosses over. (through the second order neuron which are found in the nucleus gracilis and cuneatus) - Joint position, vibration sense, fine touch (posterior column): ipsilateral during spinal cord course and then decussate at Figure 27. Brodmann’s Areas for Cortical Regions of Cerebrum Nucleaus Gracilis and Cuneatus (2nd order neuron) in the (Lateral Surface) medulla via Medial Lemniscus HOMUNCULUS – “LITTLE MAN” - Vibration, joint position and temperature senses are often o Executive functioning occurs in the cerebral cortex (2 lost without prominent symptoms – 4 mm thick Mantle) - Loss of fine (discriminative) touch is usually symptomatic The Spinothalamic tract (Anterior column/Anterolateral tract) Note: Cortex - 90% Neocortex (6 layers) crosses mostly within one or two segments of entry into the post - 10% Allocortex column (through the substantia gelatinosa and ascends the - 14 – 16 billion neurons spinal cord on the contra lateral side) - Pain, course touch and temperature sense (anterior column): NOTE: In lower extremity, the sensory information reaches through decussates (2nd order neuron: Substantia Gelatinosa) almost the medial side of the cortex (somatosensory cortex). immediatelty as it enters the spinal cord. - Pinprick (pain) loss are usually symptomatic Page 9 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado V. PROPRIOCEPTION Proprioception (Position Sense) From Latin o “Proprius” – “One’s own”, “Individual” o “Capoi” – “To take a Grasp” “Sixth Sense” The sense of the relative position of neighboring parts of the body and strength of effort being employed in movement Kinesthesia or kinӕsthesia (kinesthetic sense) strictly means movement sense (tells you where your body parts Figure 28. Homunculus are or neighboring parts of the body) Sense of overall body position during movement and acceleration Kinesthetic sense Sensors: 1. Muscle spindles 2. Golgi tendon 3. Joint kinesthetic (receptors) Figure 29. The Pathway for Neural Transmission of the 5 Basic Modalities of Sensation (Somatosensory Pathway) NOTE: 2ND order neuron: Point of decussation or crossing over of fibers o Conscious sensations reach the Somatosensory cortex o Unconscious (reflex) reach only the Spinal cord or the cerebellum SOMATOSENSORY PATHWAY Figure 30. Location of the sensors for proprioception 3 long neurons: primary, secondary, and tertiary (or first, second, and thirf). o The first neuron always has its cell body in the dorsal A. PROPRIOCEPTORS (POSITION SENSORS) root ganglion of the spinal nerve (if sensation is in Muscle Spindles parts of the head or neck not covered by the cervical - Type 1a neurons: encodes limb velocity and movement nerves, it will be the trigeminal nerve ganglia or the (muscle length and the rate of change) ganglia of the other sensory cranial nerves). - Group II neurons: encode static muscle length o The second neuron has its cell body either in the Golgi Tendon Organs spinal cord or in the brainstem. This neuron’s - Type IIb afferent neurons ascending axons will cross (decussate) to the opposite - Determine the load of a limb side either in the spinal cord or in the brain stem. Joint Kinesthetic Receptors o In the case of touch and certain types of pain, the third - Ruffini and Pacinian corpuscles neuron has its cell body in the VPN of the thalamus and ends in the postcentral gyrus of the parietal lobe. - Activated when the joint is at a threshold, usually at the (Somatosensory cortex) extremes of joint position Page 10 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Figure 31. Proprioceptors (Position Sensors) Dorsal (Posterior) Column MLP - Reaches the consciousness (somatosensory cortex) (It carries proprioception aside from fine touch and vibration) - Somatosensory cortex sends back the information to the cerebellum for control/modulation of movements Figure 32. Dorsal Column – Medial Lemniscus Pathway B. CONSCIOUS VS NON-CONSCIOUS PROPRIOCEPTION Dorsal Column – Medial Lemniscus Pathway - Reaches the somatosensory cortex (Conscious) - Aware of body position Spinocerebellar (Dorsal and Ventral) - Reaches up to cerebellum only (Non-Conscious) - e.g. Righting Reflex - Cerebellum is the main control for balance and coordination Spinal Reflex Arc - Reaches up to the spinal cord only (Non-Conscious) Figure 33. Proprioceptive Inputs - e.g. Patellar Reflex ROLE OF VESTIBULOCOCHLEAR NERVE IN MAINTAINING BODY C. PROPRIOCEPTION INPUTS POSITION: Skeletal muscles, joints, tendons, ligaments CRANIAL NERVE VIII: VESTIBULOCOCHLEAR NERVE - Via proprioceptors (Muscle spindle/golgi tendon organ/joint - Purely sensory nerve (sends afferent information to the kinesthetic receptors) – Information travels thru the: cerebellum) ▪ Dorsal Column (Conscious) - Transmits sound and equilibrium (balance) information from ▪ Spinocerebellar Tracts (Non-Conscious) the inner ear to the brain ▪ Spinal Reflex arc of the spinal cord (Non-Conscious) - Nuclei in the pontomedullary junction consist mostly of Vision bipolar neurons Vestibular System - 2 divisions: o Cochlear Nerve (Hearing) Note: All information inputs go to and is integrated into the o Vestibular Nerve (Equilibrium/Balance) - Vestibular ganglia cerebellum (also known as little brain) ▪ Nuclei: Cell bodies of bipolar neurons - Five sensory organs: Hair cells ▪ 3 cristae in the ampullae of the semicircular canals – afferent receptor in response to rotational acceleration ▪ Maculae in the saccule – vertical acceleration Page 11 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado ▪ Maculae in the utricle – linear acceleration B. PYRAMIDAL SYSTEM - Brainstem towards the Cerebellum via the cerebellar peduncles - Involved in control of motor functions in the body - Proprioception – DCML and Spinocerebellar tracts - Voluntary: Conscious (Information comes from the motor - Vision – Superior Colliculi cortex) - Vestibular – Inferior Colliculi Pyramidal pathways o Corticobulbar tracts (Brainstem – Cranial Nerves) 1. Movement of muscle in the head and face (Eg: facial expression, mastication, tongue, etc.) 2. Cortex-medulla oblongata o Corticospinal tract (Spinal Cord – Spinal Nerves) 1. Tracts of the motor cortex that reach their targets travelling to the spinal cord thru the pyramids of the medulla (where they decussate to the other side) 2. Movement of muscles below the head with control from opposite side of the brain CORTICOBULBAR TRACTS Descending tracts for Cranial Nerves CN: V3, VII (Pons) CN: IX, X, XII (Medulla) 50% decussate at the pyramids Nerve cell bodies (Nucleis) UMN Figure 34. The Parts of the Internal Ear ▪ Trigeminal Motor Nucleus – Innervate the muscles of mastication (CN V3) VI. DESCENDING MOTOR PATHWAYS The Descending Motor Pathways ▪ Facial Motor Nucleus – Innervate the muscles of facial expression (CN VII) Sensory neuron (Afferent) ▪ Nucleus Ambiguous – Innervate the soft palate, - Receive sensory input pharynx, and larynx (Speech and swallowing; CN - Conduct impulses towards the CNS IX, X) Interneurons Innervates cranial motor nuclei of the CNs bilaterally - Interconnectors except: - Establish neuronal circuit between sensory and o Innervation from contralateral cortex (Lower facial motor neurons nuclei and Genioglossus) Motor Neurons (Efferent) - Conducts impulses from the CNS to the muscles and glands C. DESCENDING SPINAL PATHWAYS o Synapse with ventral (anterior) horn interneurons A. PRIMARY MOTOR AREA a. Pyramidal Tracts: - Precentral gyrus of the frontal lobe Lateral corticospinal – cross in pyramids of medulla; - Precise, conscious, or voluntary movement of skeletal voluntary motor limb (extremity) muscles muscles Ventral (anterior) corticospinal – cross at spinal - Large neurons called pyramidal cells (Betz cells) cord; voluntary to axial/trunk muscles (muscles of - Their axons: from massive pyramidal or corticospinal tracts the chest, abdomen and back) o Descend through brain stem and spinal cord b. “Extrapyramidal” Tracts refer to all the descending o Cross to contralateral (the other) side in the medulla tracts other than the corticospinal tracts. o Therefore: right side of the brain controls the left side of Eg. Rubrospinal tract, tectospinal, vestibulospinal, the body, and the left side of the brain controls the right reticulospinal tracts side of the body Page 12 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado o Chiefly found in reticular formation of the medulla targeting lower motor neurons in spinal cord o Further modulation in the CNS: o Nigrostriatal Pathway/Corpus Striatum/Substantia Nigra o Subthalamic Nucleus/Red Nucleus o Basal Ganglia o Cerebellum o Vestibular Nuclei o Sensory areas of the Cortex 1. Rubrospinal tract 2. Pontine Reticular tract 3. Medullary Reticulospinal tract 4. Lateral Vestibulospinal tract 5. Tectospinal tract 6. Olivospinal tract Figure 35. Descending Spinal Pathways. Extrapyramidal Symptoms Disorders: Parkinson’s Disease, Chorea, Hemiballismus, THE PYRAMIDAL (CORTICOSPINAL) TRACT Athetosis, Tics Lateral CST: Limb/extremity muscles Symptoms Anterior (Ventral) CST: Trunk/axial muscles o Dystonia – continuous spasms and muscle contractions Lesions restricted to the corticospinal tracts produce the o Akathisia – motor restlessness following clinical signs: o Parkinsonism – rigidity, stooped posture The Babinski sign is present o Bradykinesia – slowness of movement The superficial abdominal reflexes are absent o Tardive dyskinesia – involuntary muscle movements The cremasteric reflex is absent. of lower face and distal extremities There is loss of performance of fine-skilled voluntary movements Lower Motor Neuron Lesions VII. CLINICAL APPLICATIONS The following clinical signs are present with lower motor neuron lesions: There are 2 types of Spinal Cord Injury Flaccid paralysis 1. Complete Spinal Cord Injury -total loss of both ascending Atrophy and descending fiber tracts in the spinal cord; both motor Loss of reflexes and sensory functions are affected Muscular fasciculation 2. Incomplete Spinal Cord Injury – there is some Muscular contracture (This is a shortening of the paralyzed preservation either of the motor or sensory function muscles. It occurs more often in the antagonist muscles below of the spinal cord injury whose action is no longer opposed by the paralyzed muscles.) Paraplegia : Paraplegia is a paralysis of the two lower limbs. Quadriplegia : Quadriplegia is a paralysis of all four limbs. EXTRAPYRAMIDAL SYSTEM (Do not cross or pass through the pyramids of the medulla) Part of motor system involving involuntary actions o Reflexes, locomotion, complex movements, postural control o Modulation and regulation (Indirect control) of anterior (ventral) horn cell of the spinal cord (without directly innervating the motor neurons) Page 13 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Figure 36. Types of SCI by severity of Injury. TYPES OF COMPLETE SPINAL CORD INJURIES Figure 38. Complete Quadriplegia/Tetraplegia. Total disruption of C3-C4 Figure 37. Complete SCI by level of injury. C4 Injury called Quadriplegia or Tetraplegia - Both the upper and lower extremities will be paralyzed - Complete motor and sensory loss below the lesion C6 Injury – will result to quadriplegia with a partial paralysis of the hands and arms (total loss of function in the lower body/extremity) Note that injuries from thoracic level below have no effect to the upper extremity but the patient will have paraplegia T6 Injury - paralysis below the chest and complete sensation loss below the lesion Figure 39. Complete Quadriplegia/Tetraplegia – all extremities are totally no movement and sensory function L1 injury - paralysis below the waist **SPINAL CORD IS COMPLETELY CUT Page 14 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado A. ANTERIOR CORD SYNDROME Figure 42. Anterior Cord Lesion. - Below the level of injury: Motor paralysis/paresis bilaterally because both ventral Figure 40. Complete Paraplegia (Thoracic level injury) horn and the corticospinal tract are both damaged T6 spinal cord is completely cut; complete/total sensory loss below Loss of pain and temperature bilaterally the level of T6 Preserved DCML; fine touch, vibration, and proprioception (position) sense TYPES OF INCOMPLETE SPINAL CORD INJURIES Bilateral lower motor neuron paralysis ln the segment of the lesion and muscular atrophy ls INCOMPLETE SPINAL CORD INJURIES caused by damage to the neurons in the anterior – there is some retention of function below the level of the lesion gray columns Bilateral loss of pain, temperature, and light touch sensations below the level of the lesion are caused by interruption of the anterior and lateral spinothalamic tracts on both sides. Tactile discrimination and vibratory and proprioceptive sensations are preserved because th e posterior white columns on both sides are undamaged. Figure 41. Incomplete Spinal Cord Injuries. Figure 43. Sensory Input (blue) and Motor output (black). Page 15 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Both the corticothalamic tract and spinothalamic tract are column on the same side of the lesion. completely damaged; Posterior column remain intact Contralateral loss of pain and temperature sensations below the level of the lesion is due to destruction of the crossed lateral spinothalamic Posterior Column – Medial Lemniscus Pathway tracts on the same side of the lesion. Because the tracts cross obliquely, the sensory loss occurs two Position or three segments below the lesion distally. Contralateral but not complete loss of tactile sensation below the level of the lesion condition Vibration Is caused by destruction of the crossed anterior spinothalamic tracts on the side of the lesion Fine Touch Because the tracts cross obliquely, the sensory impairment occurs two or three segments below the level of the lesion distally. The contralateral Anterolateral System – Lateral Spinothalamic Tract loss of tactile sense Is incomplete because discriminative touch traveling in the ascending tracts In the contralateral posterior white column Pain remains intact Temperature C. POSTERIOR CORD SYNDROME - Below the level of injury Crude & Light Touch Motor function preserved Loss of DCML functions bilaterally; Fine touch, vibration, and proprioception (position) sense Preserved pain and temperature bilaterally B. LATERAL HEMISECTION/ BROWN SEQUARD SYNDROME - Below the level of injury Motor weakness or paralysis on ipsilateral side (Hemiparaplegia/paresis) Loss of all sensory modalities on ipsilateral (same) side Loss of pain and temperature from the contralateral/opposite side (Hemianesthesia) D. CENTRAL CORD SYNDROME - Most common due to syringomyelia - Usually seen in Cervical Spinal injuries Motor Impairment: Upper Extremity > Lower Extremity Variable Sensory Loss lpsilateral lower motor neuron paralysis in the segment of the lesion and muscular atrophy are caused by damage to the neurons on the anterior gray column and possibly by damage to the nerve roots of the same segment. lpsilateral loss of tactile discrimination and of vibratory and proprioceptive sensations below the level of thelesion are caused by destruction of the ascending tracts In the posterior white Page 16 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Bilateral lower motor neuron paralysis in the segment of the THE THREE HORNS OF GRAY MATTER lesion and muscular atrophy is caused by damage to the neurons Jn the anterior gray columns (I.e., lower motor 1. Ventral Horn neuron) and possibly by damage to the nerve roots of the - also called the Anterior Horn same segment - houses somatic motor neuron cell bodies (ventral In bilateral loss of pain, temperature. light touch, and horn cells) where axons exit and innervate pressure sensations below the level of the lesion with characteristic sacral "sparing," because the ascending skeletal muscles fibers in the lateral and anterior spinothalamic tracts are - at the thoracic region, supplies intercostal also laminated, with the upper limb fibers located medially muscles and small in the exterior and the lower limb fibers located laterally, the upper limb - at the cervical region, innervates the upper limbs fibers are more susceptible to damage than the lower limb - at the lumbar and sacral region innervates the fibers lower limbs - ventral horns of the cervical and lumbosacral are Small lesions as in syringomyelia (collection of fluid filled cyst in bigger than the thoracic as more motor neurons the central cord) innervate the limbs 2. Lateral Horn - also called the intermediate Horn - house visceral motor neuron cell bodies where axon exits at the ventral route and innervates viscera and some organs - not located at every segmental spinal cord level - located between T1 and L2 spinal cord levels where all sympathetic neurons arise - also located between S2 and S4 spinal cord levels where parasympathetic neurons arise. - not present in cervical and parts of lumbar region 3. Dorsal Horn Loss of pain and temperature at the level of the lesion - also called the posterior Horn bilaterally (note: Spinothalamic tract cross the midline) - receive sensory neuronal input both somatic and with preserved fine touch, joint position, and vibration visceral sense – Dissociated sensory loss - sensory going to the dorsal root and brings information to the dorsal horn. VIII. SUPPLEMENTAL INFORMATION SPINAL CORD GRAY MATTER SPINAL CORD WHITE MATTER - appears due to cell bodies, dendrites, and synapses - White matter surrounds the periphery of the gray - internally located in the butterfly shaped structure matter - axons are myelinated because of oligodendrocyte and goes up and down - increases when it ascends and decrease when it descends - consists of tracts of axons that carry sensory information that enter each segmental level and ascend towards the brain in tracts of white matter - information from the brain descends in white matter tracts to each segmental spinal cord level Figure 44 : The gray matter and its parts. Page 17 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado SPINAL CORD SEGMENTS 1. Cervical Spinal Cord o wide-flat cord o abundance of white matter o ventral horn enlargement Figure 45: The white matter and its ascending and descending axons. PRIMARY WHITE MATTER TRACTS Figure 47: Cervical spinal cord. 1. Dorsal Column 2. Thoracic Spinal Cord o Ascending, ipsilateral sensory tracts for fine touch, o small ventral horns proprioception and vibration o only one with lateral horns 2. Anterolateral system o Ascending, contralateral sensory tracts for pain, temperature and touch. 3. Corticospinal tract o Descending, ipsilateral motor tracts on route to the ventral horn gray matter. Figure 48: Thoracic spinal cord. 3. Lumbar Spinal Cord o large ventral horns o rounded in shape Figure 46: The primary white matter tracts. Figure 49: Lumbar spinal cord. Page 18 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado 4. Sacral Spinal Cord o large ventral horns Thoracic Vertebrae o least amount of white matter -Hold the rib cage and protect the heart and lungs o smallest section of spinal cord -Limited range of motion Lumbar Vertebrae - bear the weight of the upper body - larger to support the stress, especially when lifting something heavy Sacral Vertebrae -Connect the spine to the hip bone -Vertebrae are fused together -Together with the hip bones (and the coccyx), they formthe pelvic girdle Coccyx -Four fused bones -Provide attachment points for ligaments and muscles Figure 50: Sacral spinal cord. of the pelvic floor Note: All the sensory neuron from cervical, thoracic, lumbar and sacral Parts of the Vertebrae go to each segmental part of spinal cord. 1. Body - bears weight 2. Vertebral Arch - houses the spinal cord 3. Processes - allow for muscle attachment VERTEBRAL COLUMN ANATOMY Under each pedicle, spinal nerves exit and pass throughthe Intervertebral Foramena. 7 bony processes arise from each vertebral arch to for facet joints and processes for muscle attachment. Facetjoints allow for back Each vertebrae have 2 pairs of facet joints: Intervertebral disc - provides cushioning and prevent the bones from rubbing together. Note: there is no intervertebral disc between C1 and C2. Annulus - composition of IVD, made up of layers (laminae) of fibrocartilage Nucleus - gel filled center of the IVD, distributes the Figure 51: Vertebral bone. pressure evenly in each disc during compression. Spine is also called Backbone or Vertebral Column. It is Composed of proteoglycans. composed of 33 bones (vertebrae). Function: 1. provide body with support THE CORTICOSPINAL TRACT 2. protect spinal cord from injury Vertebrae can be divided into 5 groups: Corticobulbar Tract - cerebral cortex down to the bulb 1. Cervical (C1 - C7) - pons-medulla – is called the bulb 2. Thoracic (T1 - T12) - pons synapse to trigeminal and facial motor nuclei 3. Lumbar (L1 - L5) o Facial Motor Nuclei – unique in clinical 4. Sacral (S1 - S5, fused) testing (Bell’s Palsy) 5. Coccyx (4, fused) - medulla synapse with hypoglossal nucleus and Cervical Vertebrae nucleus ambiguus. -Function: supports the head -C1 and C2 - specialized vertebrae which allows for the Corticospinal Tract – in the cerebral cortex to the spine greatest range of motion of all the vertebrae. - UMN arises and descend down to spinal cord and 50% of them synapse with lower motor neuron on -C1 (Atlas) - ring shaped and attaches directly to the ipsilateral side and 50% decussate and synapse with skull,allows to nod the head lower motor neuron at contralateral side -C2 (Axis) - serves as an axis around which C1 pivots. - primary pathway for voluntary willed motor control Thepivot of C1 on C2 is because of a specialized process and consists 2 neurons: called the Dens, or odontoid process (on C2). Page 19 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado Figure 52: The corticospinal tract and its neurons. Figure 54: The Upper Motor Neuron and its decussation. 1. UPPER MOTOR NEURON How do we identify in sections of SC that are damaging where the - arises at CNS in the cerebral cortex corticospinal tract is located? - axon descends to the internal capsule of brainstem and at - it is in the dorsal horn at the lateral white matter the level of pyramid, decussates to the contralateral side and continues downward and synapses with spinal cord 2. LOWER MOTOR NEURON with lower motor neuron - cell body in the ventral horn of the gray matter - descend its segmental spinal cord level to synapse the LMN - Axon exits via the ventral root to ventral ramus and out to and the ventral horn at some segmental level synapse in the skeletal muscle resulting to movement - cell bodies send axon to the internal capsule thru the midbrain, to the pons, and to medulla - in the middle of the cerebral peduncles of the midbrain, the corticospinal tract descends to the pons and pons proper, to the medulla and to the pyramids o pyramids- where decussation occurs - 90% of all UMN decussate at the bottom of the pyramids to the contralateral side and is called the Lateral Corticospinal Tract of the white matter of SC - 10% stays ipsilateral and is called the Anterior Corticospinal Tract Figure 55 : The lower motor neuron and its pathway. - Cross section of L4 spinal cord level where LMN synapse with muscle of neuro-muscular junction o neuromuscular junction ▪ acted by acetylcholine (Ach) in Figure 53: The upper motor neuron. disjunction ▪ an action potential basically goes down this lower motor neuron junction Page 20 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado synapse causing the release of acetylcholine in the neuromuscular junction synapse ▪ neurotransmitter Ach is going to bind to nicotinic cholinergic receptors ▪ resulting in muscle contraction Figure 58: Lumbar Region of Somatotopic organization. THE PYRAMIDAL AND EXTRA-PYRAMIDAL SYSTEM 1. Pyramidal System - is also referred to as the corticospinal tract because the upper motor neuron cell body is called the pyramid cell for the big ones and the axon decussate at the pyramids in the pyramidal system is the direct system Figure56 : The release and binding of Ach to the receptors in LMN. Somatotopic organization of ventral horn gray matter - in the cervical region, extensors are closed to the front, flexors close to the back, axial at the medial, and distal at lateral side Figure 59: The pyramidal and extra-pyramidal system. 2. Extra-Pyramidal System - also referred to as the indirect system - are the two other systems that are indirect the Figure 57: Cervical Region of Somatotopic organization. way that they influence the corticospinal tract, the basal ganglia and cerebellum - in the lumbar region, extensor is anterior, flexor is o basal ganglia posterior, axial is medial, and distal is on the ▪ caudate nucleus, putamen, and lateral side globus pallidus in the deep cerebral hemispheres ▪ indirect pathway influences willed, voluntary movements provides input to the thalamus Page 21 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado o cerebellum ▪ provides smooth, coordinated movements (posture, balance, coordination) ▪ provides input to the thalamus LESIONS - above the decussation produce contralateral deficits - below the decussation produce ipsilateral deficits UMN - lesion anywhere from the cortex down to the white matter of spinal cords which affects many muscles, all muscles below the lesion - Babinski sign o is one of the signs in adults with UMN lesion where large toe dorsiflexes / extends and the lesser toes curved/flexed o normally toes curve o normal in newborn because their white Figure 61: Lesion at the right cerebral peduncle. matter is not fully myelinated until 12 months o named after Joseph Babinski who is a polish- French trained neurologist TEST YOURSELF LMN - limited number of muscles affected because it is 1. Horner’s syndrome is the damage to the lateral horns, only in the segmental level characteristic features of HS include, except? - muscle weakness, paralysis a. Ptosis - hypotonia or flaccid muscles b. Anhidrosis - prominent muscle atrophy c. Mydriasis - hyporeflexia and fasciculations d. Miosis 2. Connects the two halves of the spinal cord and surrounds the central canal. a. Lateral Horn b. Gray commissure c. White commissure d. Spinocerebellar tract 3. True or False. Spinal cord white matter has two primary tracts? 4. True or False. Cervical Spinal Cord has lots of white matter, white flat cord and small ventral horn 5. What vertebrae holds the rib cage that protect the heart and lungs a. lumbar b. thoracic c. sacral d. coccyx 6. Below the level of injury, there is hemiparesis and hemianesthesia. a. central cord b. posterior cord Figure 60: Lesion of the right corticospinal tract at L4. c. anterior cord d. lateral hemisection Page 22 of 23 [NEUROSCIENCE 1A] 1.16 SPINAL CORD – Dr. Allan Viado 7. A condition due to spinal cord injury which is most common due to syringomyelia. a. central cord syndrome b. lateral cord syndrome c. medial cord syndrome d. distal cord syndrome 8. The following conditions show extrapyramidal symptoms except a. Parkinson’s Disease b. Chorea c. Hemiballismus d. Nystagmus 9. The following are proprioception units except: a. Skeletal muscles b. joints c. ligaments d. NOTA 10. True or False. The include the pyramidal, extra-pyramidal, and intra-pyramidal systems. Answer key: 1. C 2. B 3. False 4. False 5. B 6. D 7. A 8. D 9. D 10. False Page 23 of 23