Spinal Cord, Ascending Tracts & Sensation PDF

Spinal Cord, Ascending Tracts & Sensation Neuroanatomy: An Illustrated Colour Text...

Spinal Cord, Ascending Tracts & Sensation Neuroanatomy: An Illustrated Colour Text Introduction & Overv iew Dr Erin Fillmore https://www.clinical key.com/stude nt/content/toc/3-s2.0 31 -C201600419 Associate Professor of Clinical Anatomy Warwick Medical School | UK E Fillmore  Objectives This session addresses several of the learning objectives related to Week 3.1 E Fillmore  Overview of Parts Part 1: Sensory Receptors, Sensory Cortex, Overview of Ascending Tracts Part 2: Dorsal Column Pathway Part 3: Spinothalamic Tract Part 4: Spinocerebellar Tracts Part 5: Problem Set E Fillmore  Part 1: Sensory Receptors, Sensory Cortex, Overview of Ascending Tracts E Fillmore  Sensory Receptors & Modalities Different types of sensation are detected by different types of sensory receptors Receptors are located at multiple levels within tissues ngers Run your fi over your what keyboard… tell you receptors h key where eac edge is at? Meissner Corpuscle Discriminative touch Muscle Spindles Muscle stretch receptor Pacinian corpuscle Ruffini Ending Merkel Discs Free nerve endings Deep Pressure & Vibration Touch Light, sustained touch Pain & temperature Mechanoreceptors (distortion) Sheer stress/forces (slowly adapting) E Fillmore  Sensory Receptors: Adaptation Sensory receptors overlap so the same patch of skin can detect different stimuli Receptors have different functions and speeds of adaptation Receptor type Function Adaptation Temperature Rapid Free nerve ending Pain Slow Meissner corpuscle Discriminative Touch Rapid Merkel cells & disk Light Touch Slow Ruffini ending Touch Slow Pacinian corpuscle Deep pressure Rapid ++ E Fillmore  Functional Areas of the Cortex Sensory cortexes sit within the left and right PARIETAL lobes Primary somatosensory cortex Behind (Post-Central Gyrus) w ha t s do e s t ulcus Receives contralateral sensory input from the so m a t h e pr i o se ns o m a ry body (including taste) ry cort ex si t ? Superior Parietal Lobe Integration of sensory inputs, sensory memory, perception of contralateral self/world E Fillmore  Handed Functionality of the Brain MANY functions of the brain are crossed over! Anterior/Rostral L R l, each In genera re e re b ra l hemisphe c s sensation perceives ntrols the co from, and s of, the nt moveme l) s ite (c o n tralatera oppo e body side of th Looks Looks after the after the right side left side of the of the body body Brain viewed from above E Fillmore  Sensory Cortex: Homunculus (Somatotopic Mapping) The sensory cortexes on both the right and left side of the brain have body regions mapped onto them in a SPECIFIC pattern! er: d y Lo Rememb bo o f cortical ks The a m o u n t o n of af rea a regio e te si d su rfa c e a rr nal to e ts is p roportio nds ft ig g t (e.g. Ha e ht the b o dy p a r sitive r l h more sen te si d ar e m u c o f e yo u r k n ee cap, s s a of than eal ok m o re cortical r o bo g e t L dy estate!) RIGHT LEFT Coronal Section E Fillmore  Internal Capsule Dense collection of white matter (myelinated axons) that carry sensory and motor tracts to and from the cortex Coronal Section through Cerebrum Corona Radiata ? ? Corpus Callosum Left Posterolateral View of e mb e r the 3 types Rem s in ction fibre interconne ? the cortex rnal is the inte What TYPE orpus Internal Capsule capsule? C Callosum? E Fillmore  Internal Capsule: Somatotopic Organization Internal Capsule is somatotopically organized and contains ascending/descending white matter tracts Anterior/Rostral Anterior Limb Contains descending fibres (frontopontine, frontothalamic) Genu Motor - HEAD Motor - ARM Motor - LEG Posterior Limb SENSORY VISION/HEARING Retrolenticular Left Posterolateral View What T WO nu togeth c er mak lei ‘lentifo e rm nuc the.g. leus’? Damage (e our) to the stroke/tum psule will internal ca idespread produce w eral contralat RY d/or SENSO MOTOR an symptoms E Fillmore Posterior/Caudal  General Structure of Ascending Sensory Pathways Sensory tracts consist of a THREE neuron chain from the periphery to the primary sensory cortex Damage ca n o ccu Leg A N YW H E r Arm path – e RE along the nsure yo able to fi u’re Head gu re out what SID 3rd Order Neurons E sympt will be o o ms Leave Thalamus to ascend to cortex Thalamus n… via internal capsule VPL Thalamus VPM Note: sensory pathways synapse in the Thalamus FACE 2nd Order Neurons Decussate (at various levels) to ascend to thalamus in tracts known as a ‘lemniscus’ Medulla 1st Order Neurons Enter spinal cord via the dorsal root, ascend ipsilaterally (various ways and various distances) Spinal cord ARM / LEG E Fillmore  Thalamus: Somatosensory Nuclei The two thalami (left and right) represent an organised collection of subcortical relay nuclei There are TWO main nuclei for somatosensory input: 1. VENTRAL POSTERIOR LATERAL NUCLEUS (VPL) 2. VENTRAL POSTERIOR MEDIAL NUCLEUS (VPM) Left thalamus from a lateral perspective Anterior Posterior T T Ventral Posterior Medial nucleus Ventral Posterior Lateral nucleus VPM VPL (Sensory Face – CN V) (Sensory - Body) E Fillmore  Spinal Cord: Basic Cross Sectional Structure Grey matter is predominantly surrounded by white matter Axial sections of the spinal cord (when viewed in isolation) are viewed as if looking at them from ABOVE – this goes against the normal standard for viewing axial CT / MRI DORSAL (Posterior) Grey matter Cell bodies White matter Axons RIGHT LEFT Overvi ew Structu of Internal re of S pinal https:// C o r d : m/studewww.clinicalke -s2.0-B9 nt/content/bo y.co 0 0 8 8 # h 7 8 0 7 0 2 0 7 4 6 ok / 3 l000040 2 200 6 VENTRAL (Anterior) CENTRAL CANAL (CSF) ANTERIOR WHITE COMMISSURE E Fillmore  Spinal Cord: Grey Matter Organization The sensory dorsal horn and the motor ventral horn are organised into zones with different functions (Rexed Lamina) These areas are where the ascending (sensory) or descending (motor) fibres may synapse onto other neurons (thus cell bodies are found in these regions) e ack to th Tract of Lissauer We wil l c o m e b ys an of L is s auer (it pla Tract t role in t he importan ic Tract!) o th a la m Spin I – Pain temperature and touch VIII & IX – Lower motor neurons E Fillmore  Spinal Cord: White Matter Organization White matter can be grouped into 3 funiculi (bundles of more than one tract) Axial section of spinal cord Dorsal funiculus Dorsal Lateral funiculus Ventral ow d y o u rself of h Ventral funiculus Remin y e vs. gre rd the whit in t h e spinal co matte r us g e s in the vario cha n regions: VqR /y o ut u.b e/Ta8H00 https:/ RA E Fillmore  Spinal Cord: Ascending Tracts All tracts shown are found on BOTH sides of the spinal cord Axons in white matter are organized into fasciculi (bundles) sharing similar functions Dorsal Column Pathway LE G & S M S N AR TR U & K K R UN ( B elo T bov ) Lissauer’s Tract (A 6 ) w T6 e T Axial section of spinal cord Spinocerebellar Tracts Spinothalamic Tract E Fillmore  Major Ascending Sensory Pathways: Overview DISCRIMINATIVE MEISSNER’S, DORSAL TOUCH & VIBRATION MERKEL’S, PACINIAN, RUFFINI & JOINT COLUMN Proprioceptors PATHWAY CONSCIOUS PROPRIOCEPTION PAIN & TEMPERATURE FREE SPINOTHALAMIC NERVE ENDINGS TRACT SIMPLE TOUCH MUSCLE SPINDLES & SPINOCEREBELLAR UNCONSCIOUS GOLGI TENDON ORGANS TRACTS PROPRIOCEPTION E Fillmore  Follow-Up Questions: 1. What are the different types of sensory receptors and their sensory modalities? 2. Where is the sensory cortex located? 3. What fibers are contained within the internal capsule and how is this structure organized? 4. Describe the white and grey matter organization of the spinal cord. 5. Describe the main characteristics of the 3 ascending sensory tracts, including the sensory modalities they convey. E Fillmore  Part 2: Dorsal Column Pathway E Fillmore  Dorsal Column Pathway DISCRIMINATIVE MEISSNER’S, DORSAL TOUCH & VIBRATION MERKEL’S, PACINIAN, RUFFINI & JOINT COLUMN Proprioceptors PATHWAY CONSCIOUS PROPRIOCEPTION E Fillmore  Dorsal Columns: Fasciculus Cuneatus & Gracilis DISCRIMINATIVE TOUCH, VIBRATION and CONSCIOUS PROPRIOCEPTION Right Dorsal Columns Fasciculus Cuneatus Fasciculus Gracilis From above ~T6 From below ~T6 Graceful Legs E Fillmore  Dorsal Columns Pathway DISCRIMINATIVE TOUCH, VIBRATION and CONSCIOUS PROPRIOCEPTION 3rd order neurons travel to their respective somatotopic area on the primary sensory cortex Cortex R L Thalamus 2nd order neurons ascend to ventral posterior lateral nucleus (VPL) of thalamus & synapse with 3rd order neurons Brainstem (cerebellum removed for clarity) Medulla 2nd order neurons decussate and ascend to thalamus 1st order neurons synapse with 2nd order neurons in the lower medulla unk R limb & Tr Left upper limb (ABOVE T6, enters the more lateral Fasciculus Cuneatus) UPPE Spinal Cord 1st order neurons pass into dorsal cord and ascend ipsilaterally to lower medulla Left lower limb (BELOW T6, enters the more medial Fasciculus Gracilis) mb & LOWER li Trunk E Fillmore  Dorsal Columns Pathway: ‘Medial Lemniscal’ Frist order neurons synapse in Medulla @ respectively named nuclei and then decussate as second order neurons (collectively called the medial lemniscus) to the VPL of Thalamus Cortex R L WHAT Thalamus about the Medial Lemniscus FACE? !? Brainstem Medulla Nucleus gracilis Nucleus cuneatus k E R limb & Trun UPP Fasciculus Cuneatus Spinal Cord mb & Fasciculus Gracilis LOWER li Trunk E Fillmore  Sensory & the Face: Trigeminothalamic Tract Sensory information from the face enters the brainstem along the Trigeminal nerve, CN V Passes to the contralateral (VPM) of the Thalamus, via the Trigeminothalamic Tract (trigeminal lemniscus) in the brainstem 3rd order neurons pass to the respective somatotopic area dedicated to the face, on the primary sensory cortex Cortex R L Thalamus 2nd order neurons decussate & ascend as Trigeminothalamic Tract (aka trigeminal lemniscus) to ventral posterior medial (VPM) nucleus of the thalamus Brainstem Trigeminal Lemniscus Pons 1st order trigeminal nerve sensory neurons enter pons & synapse Trigeminal Nerve (CN V) in CN V nucleus (which is very big!) R L Spinal Cord E Fillmore  Trigeminal Nerve (CN V) Sensory Nuclei in the Brainstem 3rd order neurons continue towards the face region of the sensory cortex Thalamus (VPM) 2nd order trigeminal neurons cross over at different levels and collectively become the Trigeminothalamic Tract (Trigeminal lemniscus) – that travel to the VPM nucleus of the thalamus to synapse 1st order trigeminal neurons L L R This is the pathway that ALL sensations from the face (not just touch, vibration and conscious proprioception) take to get to the cortex E Fillmore  Dorsal Column: Damage in the Spinal Cord Dorsal Column damage in the spinal cord causes ipsilateral loss of discriminative touch, vibration and conscious proprioception BELOW the level of the lesion Tertiary syphilis can C o l um n result in demyelination s ca and destruction of affecte n be d dorsal columns compre by infarcti ss i o n on, infe , or B12 ction, deficie ncy Pseudoathetosis – writhing of digits, hands and feet Sensory ataxia – leads to positive Romberg sign & stamping gait E Fillmore  What Happens with Damage…HERE? Cortex ASK THE F O LLOWING: R L 1. What sense Thalamus s would be 2. What side w lost? ould they be 3. How m lost on? ight a patien Brainstem t present? Pons CN V Medulla Fasciculus Cuneatus Spinal Cord Fasciculus Gracilis E Fillmore  R L E Fillmore  Follow-Up Questions: 1. Describe the routes taken by the dorsal column pathway, and the trigeminothalamic tract, from periphery to the sensory cortex. 2. What are some of the major causes of dorsal column damage? 3. Explain the differences between the trigeminal lemniscus and the medial lemniscus. E Fillmore  Part 3: Spinothalamic Tract E Fillmore  Spinothalamic Tract (STT) PAIN & TEMPERATURE FREE SPINOTHALAMIC NERVE ENDINGS TRACT SIMPLE TOUCH E Fillmore  Spinothalamic Tract (STT) PAIN, TEMPERATURE and SIMPLE TOUCH E Fillmore  Spinothalamic Tract (STT) PAIN, TEMPERATURE and SIMPLE TOUCH 3rd order neurons travel to primary sensory cortex Cortex R L 2nd order neurons synapse with 3rd order neurons in ventral posterior lateral (VPL) thalamic nucleus Thalamus Spinal Lemniscus Brainstem 2nd order neurons ascend in the spinothalamic tract to the ventral posterior lateral (VPL) nucleus of thalamus Spinal Cord 2nd order neurons decussate via (across) the anterior white commissure ssates 1st order neurons from body enter spinal cord, ascend ipsilaterally 1-2 vertebral levels STT decu s 2 le v e ls ABOVE it (in the Tract of Lissauer) before synapsing with 2nd order neurons 1- al n t r y in t o the spin e cord E Fillmore  Spinothalamic Tract (STT): Decussation 2nd order STT neurons decussate via the Anterior White Commissure (AFTER they have ascended 1-2 levels in the Tract of Lissauer (in yellow circle)) Rexed I Area 2nd Order Neuron n gom yelia L1 Syr i Anterior White Commissure 1st Order Neuron L3 E Fillmore  Syringomyelia: Associated Sensory Loss Cape-like distribution of pain and temperature (and simple touch) loss May be idiopathic, follow trauma or form as a result of a developmental disorder of the central nervous system (e.g. Chiari malformation) & a in , Te m perature P im ple To uch LOST S area in shaded E Fillmore  Spinothalamic Tract (STT): Somatotopic Organisation STT is somatotopically organised Sacral Spa ring Sacral Leg the a re s q uashing Arm/Thorax If we i s l eft side - n t h STT o i l l t h e patient DE w What SI feel a Neck P a i n / Te mp on? l o ss o f E Fillmore  Follow-Up Questions: 1. Describe the route taken by the Spinothalamic Tract from periphery to the sensory cortex. 2. Explain how you can get ‘sacral sparing’ with an expanding ventral horn gray mater tumor 3. Describe the somatotopic organization of the Spinothalamic Tract. 4. Describe how syringomyelia occurs, and how this would present in a patient. E Fillmore  Part 4: Spinocerebellar Tracts E Fillmore  Spinocerebellar Tracts MUSCLE SPINDLES & SPINOCEREBELLAR UNCONSCIOUS GOLGI TENDON ORGANS TRACTS PROPRIOCEPTION E Fillmore  Spinocerebellar Tracts UNCONSCIOUS PROPRIOCEPTION Dorsal Spinocerebellar tract Mainly via muscle spindles Ventral Spinocerebellar tract Mainly via golgi tendon organs E Fillmore  Dorsal Spinocerebellar Tract (DSCT) & Ventral Spinocerebellar Tract (VSCT) Spinocerebellar tracts carry unconscious proprioception to the ipsilateral cerebellum Both tracts have 2-neurons in their chains – fibres monitor muscle length, speed of contraction & tension Cortex R L R L Brainstem & cerebellum Left upper Left upper limb : limb N RULE GOLDE lesion will bellar od y A cere psilateral b in i result oms sympt Spinal Cord Vs. e i s tract in th n to th ally a lesio cord is typic loss spinal ot h er mot or db y maske symptoms Left lower Left lower limb limb VSCT DSCT E Fillmore  Spinocerebellar Tract: Damage Damage to the spinocerebellar tract in the spinal cord is rarely seen in isolation If damage occurs in the spinal cord, symptoms are normally masked by other major motor tracts being lost Y STONGL end recomm o k i n g t h e time t ta t ch t hi s story… wa Pure lesions to this tract (although rare) could be caused by Friedreich's ataxia, resulting in: Malcoordination of motor action Wide-based gait https://www.youtube.com/watch?v=zh1vGDrTC3I E Fillmore  Major Ascending Sensory Pathways: Overview ing of Ascend Overview rd Trac : ts Spinal Coalkey.com/student w.clinic 2074 https://wwook/3-s2.0-B978070 /c onte nt/b 4 0 8#hl00006 62200008 DISCRIMINATIVE MEISSNER’S, DORSAL TOUCH & VIBRATION MERKEL’S, PACINIAN, RUFFINI & JOINT COLUMN Proprioceptors PATHWAY CONSCIOUS PROPRIOCEPTION PAIN & TEMPERATURE FREE SPINOTHALAMIC NERVE ENDINGS TRACT SIMPLE TOUCH MUSCLE SPINDLES & SPINOCEREBELLAR UNCONSCIOUS GOLGI TENDON ORGANS TRACTS PROPRIOCEPTION E Fillmore  Follow-Up Questions: 1. Describe the route taken by the Spinocerebellar Tracts from periphery to the sensory cortex. 2. How many neurons are in each of the Spinocerebellar Tracts? WHY is this different than other sensory tracts? 3. If the cerebellum is damaged on one side – which side of the body will there be sensory deficits in (ipsilateral or contralateral) – and WHY? 4. What might lead to Friedreich's ataxia? E Fillmore  Part 5: Problem Set For these problems – focus on the sensory losses a patient would present with. We will eventually also consider the motor losses (when relevant), but apply your knowledge from this Watch-It to test your understanding of the major ascending sensory tracts. *At the START of the next Watch-It (Spinal Cord, Descending Tracts & Reflexes) we will go through these! But, please attempt them on your own first  E Fillmore E Fillmore Problem #1 1 Pain and temperature loss loss Pain / temperature ine touch, vibration & conscious proprioception loss 2 ine touch, vibration & conscious proprioception loss Pain / temperature loss Pain and temperature loss Pain and temperature loss 3 Given the lesion in the spinal cord below (blue hashed area) – how might a patient present, #1, 2 or 3? Fine touch, vib. & prop. loss ine touch, vibration & conscious proprioception loss  Problem #2 Given the lesion in the brainstem seen below (red circle area), how might a patient present, #1, 2 or 3? 1 2 3 Fine touch, Fine touch, vibration & vibration & conscious conscious proprioception proprioception loss and Pain loss Pain and R L temperature temperature loss loss Fine touch, vibration & conscious proprioception loss Fine touch, vibration & conscious proprioception loss Fine touch, vibration & conscious proprioception loss Pain and temperature loss Pain and temperature loss Pain and temperature loss E Fillmore E Fillmore Problem #3 R L 1 Pain and temperature loss Fine touch, vibration & conscious proprioception loss Pain and loss temperature conscious vibration & loss proprioception Fine touch, 2 Pain and temperature loss Fine touch, vibration & conscious proprioception loss 3 Pain and temperature loss Given the lesion in the thalamus seen below (red circle area), how might a patient present, #1, 2 or 3? Fine touch, vibration & conscious proprioception loss E Fillmore Problem #4 R L Pain and temperature loss Fine touch, vibration & conscious proprioception loss 1 Pain and temperature loss Fine touch, vibration & conscious proprioception loss 2 3 Pain and temperature loss Fine touch, vibration & Given the lesion in the sensory cortex below (red circle area), how might a patient present, #1, 2 or 3? conscious proprioception loss