ANA LEC - LE6 Pyramidal and Extrapyramidal Tracts PDF

LE Pyramidal and Extrapyramidal 06 ANATOMY LECTURE 03 Tracts Melissa C. Calilao, MD, DPPS, DPSA TABLE OF CONTENTS I. MOTOR SYSTEM III. Corticospinal Tract A. Pyramidal System A. Motor Neuron Lesions B. Extrapyramidal System IV. Corticobulbar Tract C. Overview of CNS Circuitry A. Facial Motor Nucleus...

LE Pyramidal and Extrapyramidal 06 ANATOMY LECTURE 03 Tracts Melissa C. Calilao, MD, DPPS, DPSA TABLE OF CONTENTS I. MOTOR SYSTEM III. Corticospinal Tract A. Pyramidal System A. Motor Neuron Lesions B. Extrapyramidal System IV. Corticobulbar Tract C. Overview of CNS Circuitry A. Facial Motor Nucleus II. PYRAMIDAL TRACT B. Hypoglossal Nucleus A. Overview of the Pyramidal Tract V. EXTRAPYRAMIDAL TRACTS B. Origin of the Tract Fibers A. Midbrain C. Motor Homunculus B. Pons/Medulla D. Paracentral Lobule VI. CASES E. Supplementary Motor Area A. Spinal Cord Lesion F. Anatomical Origin of Descending B. Brainstem Lesion Pathways C. Internal Capsule Lesion G. Reflex Arc D. Cortical Lesion VII. SAMPLE QUESTIONS C. OVERVIEW OF CNS CIRCUITRY LEGEND ⭐ 💬 IMPORTANT 1. 2. LECTURE 📖 BOOK 📋 PREVIOUS TRANS REFERENCES PDF/Lecture Topic – Prof Name (Synch/Asynch/FTF) Book Chapter: Title – Book Name by Author UMN LMN ABBREVIATIONS Upper Motor Neuron Lower Motor Neuron LEARNING OBJECTIVES Trace the pathway of the pyramidal tracts. Differentiate an upper motor vs. a lower motor neuron lesion. Discuss briefly the other descending tracts. Explain the manifestations of patients with involvement of the motor pathways. 💬 ⭐ A. PYRAMIDAL SYSTEM A descending tract Responsible for the primary control of voluntary movement carried out through two main tracts: → Corticospinal tract: Pathways for voluntary, discrete, skilled I. MOTOR SYSTEM Figure 1. Diagram of the CNS circuitry [Lecturer’s PPT] Imagine yourself in class and you wanted to ask a question. In order for you to do that, you need to raise your hand. EXECUTION OF MOVEMENT The desire to move originates in the association areas The information is then relayed to the cerebellum and basal ganglia (nuclei) → Cerebellum will funnel the information via the thalamus to the premotor and motor areas of the cerebral cortex. ◼ Premotor area: Where the “programming” or the preparation to move originates ◼ Motor area: Gives out the command to move From the motor area, command information is then processed by the: → Corticobulbar tract to the brainstem centers → Corticospinal tract to the lower motor neurons (LMN) in the spinal cord The LMN will then give the command to the voluntary muscles of your arm to execute the movement and raise your hand up. movement, especially in distal parts of limbs AFTER EXECUTION OF MOVEMENT ◼ Further divided into: Movement will now set up alterations and sensory inputs in the special senses → Information will be relayed back to the brainstem centers and cerebellum The same movement will also stimulate muscles, joints, skin, and tendons → Information will be relayed back to the cerebellum and the lower motor neurons ◼ Cerebellum also relays information to the brainstem centers as brainstem pathways are responsible for coordination and posture All of this feedback information is necessary for fine-tuning and adjustment of movement – Lateral corticospinal tract – Anterior or Ventral corticospinal tract → Corticobulbar tract B. EXTRAPYRAMIDAL SYSTEM Play a supporting role in the production of well-coordinated movements. Under this are: → Basal ganglia (nuclei) → Cerebellum Note: Extrapyramidal tracts are different from the extrapyramidal system which will be discussed in a separate lecture. ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 1 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA II. PYRAMIDAL TRACT A. OVERVIEW OF THE PYRAMIDAL TRACT Longest and largest descending fiber tract (human CNS) Concerned with voluntary, discrete, skilled movements; and control of muscles involved in speech and vocalization Fibers pass through the medullary pyramids (hence the name) → Located in the upper medulla Figure 4. Cortical surface [Lecturer’s PPT] POSTCENTRAL GYRUS Functional area: Primary somatosensory cortex Area where 1⁄3 of the axons of the pyramidal tract arise Axons coming from this area do not directly control movement More concerned with sensory input that go into the nervous system ⭐ ⭐ Figure 2. Brainstem anterior view [Lecturer’s PPT] B. ORIGIN OF THE TRACT FIBERS Pyramidal tract fibers arise from 3 areas: → 1⁄3 of axons from Precentral gyrus ◼ (BA 4) Primary Motor Cortex → 1⁄3 of axons from Postcentral gyrus ◼ (BA 3,1,2) Primary Sensory Cortex → 1⁄3 of axons from Premotor/Secondary Motor Cortex ◼ (BA 6) and some from frontal eye fields (BA 8) These 3 areas constitute the sensorimotor cortex which gives rise to the pyramidal tract ⭐ PREMOTOR/SECONDARY MOTOR CORTEX (BA 6) Functional area: Secondary motor cortex No specific name was given to the area as it is part of the frontal gyri Area where 1⁄3 of the axons of the pyramidal tract arise Located near the frontal eye fields (BA 8) Contains neurons that specifically influence eye movements ⭐ C. MOTOR HOMUNCULUS Somatotopic representation of the body on the primary motor and premotor cortex → “Soma”: Body → “Topic”: Area Each part of the body is represented on a specific portion of the primary and premotor cortex Area at the lowest lateral portion close to the Sylvian fissure features neurons that would influence and control the tongue and larynx → Ventral: Lips and face → Dorsolateral: Fingers and hands → Superior: Arms and trunk → Medial: Perineal muscles, legs, and feet ⭐ Figure 3. Sensorimotor cortex [Lecturer’s PPT] Pink: Premotor/Secondary motor cortex (BA 6), Violet: Precentral gyrus, Blue: Postcentral gyrus, Blue circle: Frontal eye field (BA 8) PRECENTRAL GYRUS (BA 4) Functional area: Primary motor cortex Area where 1⁄3 of the axons of the pyramidal tract arise Pyramidal cells of Betz → Give rise to 10% of precentral gyrus or 3% of entire corticospinal tract → Located at the 5th layer of the cortical surface → Unique because they send their axons directly to the anterior horn cells in the spinal cord As such, they are responsible for highly-skilled movements ⭐ Figure 5. Motor homunculus [Lecturer’s PPT] ANATOMY LEC | LE6 Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 2 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA ⭐ Take note of the tongue, lips, face, fingers, and hands which are represented on a much larger scale → Concerned with highly skilled movements → More neurons are needed to control these movements D. PARACENTRAL LOBULE Area surrounding central sulcus (Fig. 6 blue circle) Represents lower limbs in the motor homunculus Comprises of: → BA 4 → BA 3, 1, 2 → BA 5 2nd order neuron 3rd order neuron ⭐ CLINICAL CORRELATION (Relating to Fig. 5) Anterior cerebral artery (ACA) → Supplies the medial portions of the cerebral hemispheres → Occlusion: result to weakness in the lower extremities Middle cerebral artery (MCA) → Supplies the dorsal and lateral portions of the cerebral hemispheres → Occlusion: result to weakness in the face and upper extremities Figure 6. Medial view of the surface of the cerebral hemisphere [Lecturer’s PPT] E. SUPPLEMENTARY MOTOR AREA Located in the medial frontal gyrus on the medial surface of the hemisphere → At the most medial portion of BA 6, anterior to the paracentral lobule (Fig. 6 red circle) Plays a special role in integrating movements that are performed simultaneously on both sides of the body (Eg. Jumping jacks, skipping rope) → Stimulation results in contralateral limb movement → Needs a stronger stimulus than primary motor area ⭐ ⭐ Table 1. Neurons in the descending pathway Description Cell body location 1st order Origin of Cerebral cortex neuron command Internuncial or connecting neuron AKA Lower motor neuron (LMN) or final common pathway Anterior column of spinal cord Anterior column of spinal cord gray the gray the Axon Very long axons in the spinal cord Short axon Innervates skeletal muscles through the anterior root of spinal nerve Figure 7. Series of neurons in the descending pathway 1st order neuron (blue circle), 2nd order neuron (green arrow), 3rd order neuron (red arrow) [Lecturer’s PPT] Note: Some axons of 1st order neurons terminate directly on 3rd order neurons such as in reflex arcs G. REFLEX ARC Reflex: an involuntary response to a stimulus → Does not require processing from higher centers because the response needs to be fast → 4 components: (see Fig. 8) ◼ Receptor organ ◼ Afferent neuron ◼ Efferent/Effector neuron ◼ Effector organ Damage to any of the components would abolish the reflex F. ANATOMICAL ORIGIN OF DESCENDING PATHWAYS Control of skeletal muscle activity is carried out via a series of neurons In the descending pathway, it utilizes 3 neurons ANATOMY LEC | LE6 Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 3 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA KNEE JERK/PATELLAR TENDON REFLEX Figure 8. Monosynaptic reflex arc [Lecturer’s PPT] Receptor organ (red arrow), Afferent neuron (blue arrow), Efferent/effector neuron (pink arrow), Effector organ (violet circle) Tapping of patellar tendon using a neuro hammer would stimulate muscle spindles in quadriceps muscle Stimulus travels through the femoral nerve to reach L2-L4 segments Impulse travels through motor fibers of femoral nerve to stimulate quadriceps muscle causing a jerk-like muscle contraction and extension of the leg at the knee joint Figure 9. Corticospinal tract [Lecturer’s PPT] III. CORTICOSPINAL TRACT A. STRUCTURES INVOLVED Cerebral cortex → Origin of the 1st order neuron Corona radiata → Where axons would pass through → Collection of nerve fibers that ascend and descend → Located at the medullary substance of the cerebral cortex Internal capsule (Posterior limb) → Compact V-shaped band that opens laterally → Separates the lentiform nucleus (putamen and globus) laterally from the caudate nucleus and thalamus medially → Note: The internal capsule is best seen in the horizontal section of the cerebral hemisphere ANATOMY LEC | LE6 Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca Figure 10. Horizontal section of the cerebrum [Lecturer’s PPT] → Parts of the internal capsule: ◼ Anterior limb ◼ Genu ◼ Posterior limb – Where CST fibers would pass through – Fibers follows a somatotopic arrangement ○ Anterior: Fibers controlling the upper limbs ○ Posteriorly: Fibers controlling the lower extremities ◼ CST fibers are closely packed together – Occlusion of vessel supplying this area will result to a dense manifestation of the symptoms – Patient will experience paralysis or weakness of arms, trunk, and legs PAGE 4 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA Table 2. Differences between anterior and lateral CST Anterior or ventral CST Lateral CST Uncrossed fibers (10-15%) Crossing of fibers (75-90%) Eventually cross before Forms pyramidal decussations terminating on the anterior horn TErminate at the anterior gray cells the cervical and upper column of all spinal cord thoracic spinal segments segments Shorter tract Longer tract Figure 11. CST at the posterior limb of the internal capsule. A CST controlling the arms (A), trunk (T), lower limbs (L). [Lecturer’s PPT] Cerebral peduncles → Located at the middle ⅗ of the midbrain → Fibers have somatotropic arrangement ◼ Medially: Fibers controlling the upper limbs ◼ Laterally: Fibers controlling the lower limbs Pons → Fibers are broken up into fascicles via the transverse pontocerebellar fibers → Similar somatotropic arrangement to the midbrain Medulla oblongata → Upper medulla ◼ Fibers will form the pyramids → Caudal medulla ◼ Fibers will cross at the Pyramidal Decussation and form the Lateral Corticospinal Tract – Right motor side controls left half of the body – Left motor strip controls right half of the body ◼ Uncrossed fibers form the anterior corticospinal tract ◼ Lesions with the cerebral cortex – Above the pyramidal decussations will affect contralateral regions – Below the pyramidal decussations such as spinal cord lesions will affect the ipsilateral region Spinal cord → Ventral CST is located at the anterior funiculus close to the anterior median fissure → Lateral CST is located at the lateral funiculus of the spinal cord → Spinal cord lesions will produce paralysis on the ipsilateral side of the body since the fibers have already crossed Figure 13. Location of tracts in the spinal cord. [Lecturer’s PPT] B. PYRAMIDAL TRACT FIBER DISTRIBUTION Pyramidal tract fibers terminate mostly on the cervical spinal levels → Better motor control in the upper extremities Corticospinal tracts are not the sole pathways for voluntary movements → Forms a pathway that confers speed and agility to voluntary movements → Contribute on controlling prime mover muscles while other tracts control simple basic movements Table 3. Termination of pyramidal tract fibers. Spinal cord segment Distribution Cervical 55% Thoracic 20% Lumbar/ Sacral 25% Table 4. Points to remember. Figure 12. Anterior view of the brainstem showing the pyramidal decussation at the caudal medulla. [Lecturer’s PPT] ANATOMY LEC | LE6 Flexor muscles Extensor muscles Muscle tone Impulses to skeletal muscles Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca ⭐ Pyramidal (Corticospinal tracts) Excitatory Inhibitory Increase Initiate Extrapyramidal (Other descending tracts) Inhibitory Excitatory Inhibit Inhibit PAGE 5 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA 5/5 It is rare to have an organic lesion restricted to pyramidal or extrapyramidal only. Usually BOTH sets of tracts are affected to an extent producing clinical signs referring to both C. MOTOR NEURON LESIONS Moves muscle group with full resistance MUSCLE ATROPHY UMN lesion: No muscle atrophy initially; if the patient will not be able to have therapy or exercise, may develop disuse atrophy wherein unused muscle will eventually shrink LMN lesion: With muscle atrophy early on; due to damage to anterior horn cells which have give nutrition to the muscles they innervate (trophic effect) Types of Paralysis → Hemiplegia - one side of the body and includes the upper limb, one side of the trunk, and the lower limb → Monoplegia - one limb only → Diplegia - two corresponding limbs (i.e. both arms or both legs) → Paraplegia - two lower limbs → Quadriplegia - all four limbs FUNCTIONS OF TONE Figure 14. Cross Section of the Spinal Cord, Dorsal and Ventral Root, and Peripheral Nerve. [Lecturer’s PPT] ⭐ Table 5. UMN vs LMN Lesions Upper Motor Neuron Paresis NO muscle atrophy Spasticity in muscle tone Hyperreflexia With Clonus With Babinski (Extensor Plantar Reflex) Loss of certain superficial reflexes: Superficial abdominal Cremasteric reflex Lower Motor Neuron Complete paralysis WITH muscle atrophy Flaccidity in muscle tone Areflexia NO clonus NO Babinski Muscle Fasciculations 💬 Note: There are clinical cases wherein for instance, a patient with 💬 💬 upper motor neuron lesion will exhibit complete paralysis instead of paresis. For purposes of simplification and for 1st year level, the information in the table above is followed. Spasticity, hyperreflexia and clonus are all typical of extrapyramidal tract lesions → uninhibited pyramidal tracts Babinski and loss of certain superficial reflexes are typical of pyramidal tract lesions PARESIS VS. COMPLETE PARALYSIS UMN lesion: Paresis or weakness LMN lesion: Complete paralysis - damage is in the anterior horn cells or the final common pathway Table 6. Motor Strength Grading Grade Description 0/5 No muscle contraction 1/5 Visible contraction but no movement 2/5 Active movement when gravity is eliminated 3/5 Moves muscle against gravity but not against resistance 4/5 Moves muscle group with some resistance ANATOMY LEC | LE6 UMN lesion: Spasticity (increased tone), muscle will be stiff; due to extrapyramidal tract lesion LMN lesion: Flaccidity (no/poor tone), muscle will be easy to move; due to pyramidal tract lesion Recall: Pyramidal tracts tend to INCREASE muscle tone Extrapyramidal tracts tend to DECREASE muscle tone REFLEXES UMN lesion: Hyperreflexia (exaggerated reflexes); due to extrapyramidal tract lesion → Corticospinal tracts initiate impulses to the muscles that they innervate → Manifestation of unopposed effect of corticospinal tracts LMN lesion: Areflexia (no reflexes); damage to LMN in reflex arc Table 7. Grading of Deep Tendon Reflexes Grade Description 0 No response; always abnormal 1+ A slight but definitely present response; may or may not be normal (Note: for our purposes, normal) 2+ A brisk response; normal 3+ A very brisk response; may or may not be normal 4+ A tap elicits a repeating reflex (clonus); always abnormal CLONUS Rapid strong muscle contraction of a paralyzed limb when it is grasped firmly Can be elicited in: flexor muscles of fingers, biceps, calf, and quadriceps muscles UMN lesion: WITH clonus; due to lesion in the extrapyramidal tracts LMN lesion: NO clonus BABINSKI (EXTENSOR PLANTAR) REFLEX To elicit Babinski reflex: stroke the lateral aspect of the sole of the foot up to the base of the toes Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 6 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA ⭐ (+) Babinski: dorsiflexion of the big toe and fanning of other toes → Normal response should be plantarflexion UMN lesion: WITH Babinski (Extensor Plantar) reflex; due to lesion in the pyramidal tracts, specifically the corticospinal tracts LMN lesion: NO Babinski reflex (+) Babinski reflex is normal up to 1st year of life as the corticospinal tracts are not yet fully myelinated ⭐ Projections are bilateral: innerations from BOTH contra & ipsilateral cortex EXCEPT for 2 cranial nerves: → Facial motor nucleus (CN VII): Located at the dorsal portion of the pons close to the midline → Hypoglossal nucleus (CN XII): Spans the length of the medulla oblongata, close to the midline In exercises on localization, it is important to know the location of the nuclei of the cranial nerves, especially if the lesion is in the brainstem. LOSS OF CERTAIN SUPERFICIAL REFLEXES A. FACIAL MOTOR NUCLEUS Superficial abdominal reflex → To elicit: Scratch or stroke the abdominal muscles → Normal response: Contraction of the corresponding muscles Cremasteric reflex → To elicit: Stroke the inner aspect of the thigh of a male → Normal response: Retraction of scrotum and testes UMN lesion: loss of these reflexes; due to lesion in the pyramidal tracts, specifically the corticospinal tracts MUSCLE FASCICULATIONS LMN lesion: muscle fasciculations or twitching of the muscle; seen in conditions where there is a slow destruction of the LMN IV. CORTICOBULBAR TRACT Origin: Cerebral cortex Destination: Bulbar region or brainstem Arises from face region of primary motor cortex (BA 4), premotor (BA 6), frontal eye fields (BA 8) (Refer to Fig. 3) ⭐ Figure 15. Basal Nuclei [Lecturer’s PPT] Fibers would pass through the corona radiata, genu of the internal capsule, and terminate in the brainstem Fibers would project to: → Motor nuclei of CNs III, IV, V, VI, VII, IX, X, XI & XII ◼ Exceptions are I, II and VIII which are purely sensory → Parts of reticular formation (corticoreticular fibers) in pons & medulla; essential in the control of facial muscles when it involves emotion → Sensory relay nuclei (gracilis, cuneatus, sensory trigeminal nuclei, & nucleus of solitary fasciculus); important in controlling inputs that go into the brain ANATOMY LEC | LE6 Figure 16. Corticobulbar Tract of Facial Nucleus [Lecture PPT] Corticobulbar tract projections are generally bilateral (projecting to both sides) → Dorsal portion (red dot) innervate the upper part of the face ◼ Receives innervation from both contralateral and ipsilateral sensory motor cortex → Ventral portion (blue dot) innervate the lower half of the face ◼ Only receives innervation from contralateral sensory motor cortex Shaded areas of the face show the distribution of facial muscles paralyzed after a supranuclear lesion of the corticobulbar tract and after a lower motor neuron lesion of the facial nerve → Lesion at the left sensory motor cortex face area or corticobulbar tract fibers (labeled Supranuclear Lesion) ◼ Function on dorsal portion (upper half of face) for both sides would still be intact d/t still receiving fibers from both sides ◼ Ventral facial nerve would be affected: Contralateral weakness on the lower half of the face Upper Motor Neuron or Supranuclear Lesion → Paralysis of contralateral lower half of the face called Central Facial Paralysis Lower Motor Neuron Lesion → Paralysis of ipsilateral half of the face called Peripheral Facial Paralysis (Bell’s Palsy) (see Figure 17) More than 85% have spontaneous recovery within 1 to 2 months ⭐ ⭐ Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca 💬 PAGE 7 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA ⭐ ◼ Right hypoglossal n. will not be able to draw the root of the tongue to the left → tongue will be drawn to the right Lower Motor Neuron Lesion (Hypoglossal Nucleus, CN XII) → Tongue deviation to the ipsilateral side, atrophy → Lesion to the right hypoglossal nucleus or CN XII ◼ The action of the right hypoglossal nerve will be impaired → tongue will be drawn to the right side Drawing for better understanding: Figure 17. Presentation of Bell’s Palsy [Lecturer’s PPT] PRACTICE CASES 1. A patient upon waking up in the morning is unable to move the entire LEFT half of his face. Type of lesion? LMN Where is the lesion? Left (Ipsilateral) Diagnosis? Bell’s Palsy → Prognosis: spontaneous recovery within 1-2 months 2. A stroke patient is unable to move the LEFT lower half of the face but can still wrinkle both eyebrows. Type of lesion? UMN Where is the lesion? Right (Contralateral) B. HYPOGLOSSAL NUCLEUS Figure 19. Corticobulbar Tract of Hypoglossal Nucleus Diagram [Lecture PPT] Black Arrows indicate the corticobulbar tract and innervation while blue arrows are for the direction of the action of the tongue Mark the lesion (whether UMN or LMN) and trace the arrows to identify direction of deviation PRACTICE CASES 3. The resident noted that the tongue of a stroke patient was deviated to the RIGHT but not atrophied Type of lesion? UMN Where is the lesion? Left (Contralateral) 4. The intern noted that the tongue of a stroke patient was atrophied and deviated to the RIGHT. Type of lesion? LMN Where is the lesion? Right (Ipsilateral) 📋 [Lecture PPT] Figure 18. Corticobulbar Tract of Hypoglossal Nucleus Corticobulbar projections are largely contralateral → Hypoglossal nuclei also receive ipsilateral corticobulbar fibers to a minimal extent Hypoglossal nerve innervates the genioglossus muscle → Draws the root of the tongue to the contralateral side Upper Motor Neuron Lesion (Corticobulbar Tract) → Tongue deviation to the contralateral side, no atrophy → Lesion at the left corticobulbar tract ◼ Small amount of ipsilateral fibers will be affected, but left hypoglossal nucleus mostly receives fibers from the right corticobulbar tract → intact (L) hypoglossal nucleus, affected (R) hypoglossal nucleus ⭐ ANATOMY LEC | LE6 Table 8. Summary of lesions resulting to facial weakness [2024A] Location of lesion Location of facial weakness Right UMN (before the facial Left lower half nucleus) Left UMN Right lower half Right LMN (facial nucleus or Right half facial nerve) Left LMN Left half V. EXTRAPYRAMIDAL TRACTS A. MIDBRAIN TECTOSPINAL AND TECTOBULBAR TRACTS “Tectum” = “roof of the midbrain” Origin: Superior colliculus Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 8 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA Fibers: → Cross in the dorsal tegmental decussation in the midbrain → Incorporated in the medial longitudinal fasciculus at the spinal cord level Likened into a highway used by tracts to go up and down ◼ Extends from the mid-thoracic level up to the midbrain Termination: → LMN in the brainstem (for tectobulbar tract) → Anterior gray column in the upper cervical segments of the spinal cord (Rexed Laminae VI, VII, & VIII) Function: → Mediate reflex postural movements of head and neck in response to visual stimuli (head turning and eye movements) 💬 INTERSTITIOSPINAL TRACT Origin: Interstitial nucleus of Cajal Fibers: Only tract in the midbrain that is uncrossed → Forms part of MLF Termination: → Anterior horn of upper cervical levels of the spinal cord in Lamina VII & VIII Function: → Modulates reflex postural movements in response to visual & vestibular stimuli (similar to tectospinal and tectobulbar tracts) 💬 B. PONS/MEDULLA LATERAL VESTIBULOSPINAL TRACT Origin: Lateral vestibular nucleus Termination: → Descends in anterolateral funiculus and terminates in Rexed Laminae VII & VIII on alpha & gamma motor neurons from cervical and lumbosacral levels Alpha motor neurons - innervate the extrafusal muscles Gamma motor neurons - innervate the intrafusal muscle fibers Fibers: uncrossed Afferents: → Receives afferents from the vestibular nerve and cerebellum Function: → Maintenance of upright posture and balance → Excites extensor motor neurons innervating the neck, back, forelimb, and hindlimb muscles 💬 💬 MEDIAL VESTIBULOSPINAL TRACT Origin: Medial vestibular nucleus Termination: → descends in MLF → anterior funiculus (as far as mid thoracic level) → terminates in the same laminae as the Lateral Vestibulospinal Tract (Rexed Laminae VII & VIII) Fibers: both crossed and uncrossed Afferents: → From primary vestibular & cerebellum Function: → Maintains upright posture → Excites the neck up to the back motor neurons only ⭐ Figure 20. Tectospinal Tract (Blue), Reticulospinal Tracts (Red)[Lecturer’s PPT] RUBROSPINAL TRACT “Rubro” = “red” Origin: Red nucleus (at the level of superior colliculus) Fibers: → Cross immediately in the ventral tegmental decussation → Descend down the brainstem → Enter lateral funiculus of spinal cord Termination: → Internuncial neurons (anterior gray column) in all spinal cord levels (Lamina V, VI, VII) Function: → Influence tone control/facilitates the activity of flexor muscle groups → Functionally similar to the CST; said to assist the CST in its function ANATOMY LEC | LE6 Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 9 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA Drooping of the right half of the face, but can still wrinkle eyebrows +4 DTRs over the right upper extremity Decreased pain and vibratory sensation to right side of face and upper extremity QUESTION: WHERE IS THE LESION? Upper motor neuron lesion (UMN) or lower motor neuron lesion (LMN)? Answer: UMN Table 9. Pertinent Findings Pertinent findings Affected tracts Laterality Motor strength 2⁄5 Corticospinal tract (Probably) left right upper extremity (paresis) Drooping right half Corticobulbar tract (Definitely) left of lower face +4 DTR's right upper Extrapyramidal (Probably) left extremity tracts/Corticospinal (hyperreflexia) tract Figure 21. Vestibulospinal Tracts (Red), Rubrospinal Tracts (Blue)[Lecturer’s PPT] RETICULOSPINAL TRACTS 1. PONTINE (MEDIAL) RETICULOSPINAL TRACT Origin: Pons Almost entirely ipsilateral Descends chiefly in anterior funiculus of SC (all cord levels, Lamina VII & VIII) Facilitatory to extensor motor neurons 2. MEDULLARY (LATERAL) RETICULOSPINAL TRACT Origin: Medulla Has both crossed and uncrossed fibers Descends in both the ipsi- and contralateral lateral funiculus of the SC (ALL SC levels, Lamina VII & IX) Function is opposite of the Pontine Reticulospinal Tract: inhibitory to extensor motor neurons Provides pathway by which the hypothalamus can control the sympathetic outflow & sacral parasympathetic outflow to influence autonomic functions: → Respiration, circulation, sweating, shivering → Dilation of pupils → Sphincter muscles of the gastrointestinal & urinary tracts Decreased pain and vibratory sensation to right side of face and upper extremity MSE: Normal or Abnormal? Lateral spinothalamic DCMLS Cannot be identified yet Where is the lesion? In localizing the specific lesion, think of an area that: All tracts mentioned above will pass through All the manifestations can be explained Patient is drowsy: Abnormal MSE A. SPINAL CORD LESION ⭐ 💬 VI. CASES A 65 y/o male, hypertensive, was rushed to the UERM-ER because of right-sided weakness of the face and upper extremities. NEUROLOGICAL EXAMINATION Mental status exam (MSE): → Patient is drowsy but arousable, speaks very slowly and with effort Motor strength of 2⁄5 over the right upper extremity ANATOMY LEC | LE6 Figure 22. Spinal cord segment showing lateral spinothalamic tract and lateral corticospinal tract [Lecturer’s PPT] Ipsilateral loss of motor function → Fibers below the pyramidal decussation → If the lesion is above the pyramidal decussation, it would produce loss of motor function contralateral to the side of the lesion → If the lesion is below the pyramidal decussation, motor deficit will be seen on the same side of the lesion Contralateral loss of pain and thermal sensation below the level of the lesion → Fibers in lateral funiculus (of the lateral spinothalamic tract) are axons of N2 which have already crossed Dorsal column-medial lemniscal system (DCMLS) → Fibers cross in the medulla Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 10 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA → Symptoms should be ipsilateral to the lesion CASE EVALUATION In the patient, all of the manifestations are on the same side (right) → Not a spinal cord lesion ◼ If it were a spinal cord lesion, motor and sensory deficits should be contralateral to the side of the lesion ◼ Thus, spinal cord lesion side (R) can be ruled out SPINAL CORD INJURIES: UMN OR LMN? Symptoms → LMN ◼ Progressive muscular atrophy ◼ Paresis – UMN but take note that there will be a progressive destruction of neurons in the anterior gray (ventral) horn – Initially, the patient would present with weakness and once the neurons are completely destroyed, it will present with paralysis ◼ Fasciculations – Specific for LMN – Slow destruction of the anterior horn cells → UMN ◼ Paresis ◼ Spasticity ◼ (+) Babinski Both sets of conditions will be seen –– LMN and UMN POLIOMYELITIS Figure 23. Spinal cord injuries: UMN or LMN [Lecturer’s PPT] It could be upper or lower manifestation → NOT all spinal cord injuries would present with LMN manifestations → It could be both or could be either just LMN or UMN UMN: If only the tracts were affected → Eg. Lateral funiculus is affected LMN: If the lesion was on the anterior gray column of the spinal cord, anterior horn cells will be damaged AMYOTROPHIC LATERAL SCLEROSIS (LOU GEHRIG DISEASE) Figure 25. Poliomyelitis [Lecturer’s PPT] Acute viral infection of the neurons of the anterior gray columns of the spinal cord and cranial nerve motor nuclei affecting the LMN Lower limb muscles are affected more than the upper limbs → If you see patients with polio, you will notice that both lower limbs are affected Severe cases: Paralysis of intercostal muscles and diaphragm → Patients would have to be put in ventilators There is no treatment but there is prevention → Prevention for polio: vaccination ADDITIONAL INFORMATION: In 2000, WHO declared the Philippines as polio-free but due to the Dengvaxia scare in September 2019, the Philippines again reported an outbreak [Lecturer’s PPT] Figure 24. Amyotrophic lateral sclerosis Chronic progressive disease of unknown etiology with NO treatment Made popular because of the ice bucket challenge Rarely familial but inherited in ~10% of cases Occurs in late middle age, fatal in 2 to 6 years Affects the anterior gray column affecting the LMN On the lateral funiculus, ALS would also affect the corticospinal affecting the UMN Since both the tracts and the anterior horn cells will be damaged, the patient would present with both UMN and LMN lesion manifestations ANATOMY LEC | LE6 B. BRAINSTEM LESION With CN deficits (nerves exit ipsilateral to their symptoms) → Midbrain: CN III → Pons: CN V, VI, VIl → Medulla: CN IX, XI, XIl Clue if brainstem lesion is present → Multiple cranial nerve deficits (ipsilateral) Deficits → CN deficits: Ipsilateral to the lesion → Motor deficits: Contralateral to the lesion Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 11 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA CASE EVALUATION CASE EVALUATION May be considered as CN VIl deficit since the patient manifests weakness in the area of the face → However, facial deficit is just central facial paralysis ◼ Indicates a UMN lesion ◼ NOT a cranial nerve deficit Brainstem lesion can be ruled out since there were no cranial nerve deficits in the patient Patient was drowsy: Abnormal MSE Normal CN Motor and sensory deficits on the same side WHERE IN THE CEREBRAL CORTEX, SPECIFICALLY? Must be an area that will affect both the motor and sensory area of the face and upper extremity Lesion is in the motor and sensory cortex LATERALITY C. INTERNAL CAPSULE LESION Figure 26. Figure showing corticospinal and corticobulbar tracts in the internal capsule [Lecturer’s PPT] Posterior limb → Where fibers of the CST pass through → ATL: Arms, trunks, legs Denser symptoms → Not only see weakness of the face and upper extremities but we can also expect corresponding weakness of the lower extremities MSE should be normal Figure 28. Lesion in the left sensorimotor cortex [Lecturer’s PPT] CASE EVALUATION Patient did NOT exhibit weakness in the lower extremities → Only symptoms on the upper extremity Patient was drowsy: Abnormal MSE → Thus, lesions of the internal capsule can be ruled out D. CORTICAL LESION Figure 29. Loss of pain, thermal sensation and decreased vibratory sensation Left (contralateral side) → Lesion in the left sensorimotor cortex → Patient manifests weakness in the face and upper extremities on the right side → Loss of pain, vibratory, and thermal sensation on the right side WHAT COULD BE THE CAUSE? Embolism Stroke involving occlusion of a vessel Vessel is the middle cerebral artery (MCA) → Supplies the area of the face and upper extremities Figure 27. Sensory and motor Homunculus [Lecturer’s PPT] Cerebral cortex is affected Abnormal MSE Normal CN Motor and sensory deficits should be ipsilateral ANATOMY LEC | LE6 VII. SAMPLE QUESTIONS 1. The corticospinal tract fibers to the lower extremities pass through which part of the internal capsule? a) Genu Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 12 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA b) Distal posterior limb c) Proximal posterior limb d) Proximal anterior limb 2. The medullary reticulospinal tract functions as: a) Facilitatory to extensor motor neurons b) Inhibitory to flexor motor neurons c) Facilitatory to flexor motor neurons d) Inhibitory to extensor motor neurons 3. Cells found at the 2nd layer of cortical surface a) Pyramidal cells b) Stellate cells c) Large pyramidal cells of Betz d) Small pyramidal cells 4. An occlusion at the lateral aspect of the cerebral hemisphere results in a weakness on which body part? a) Legs b) Feet c) Thigh d) Arms 5. Fasciculations are seen in cases where there is slow destruction of the anterior horn cells. It can only be seen in patients with: a) Lower motor neuron lesion b) Upper motor neuron lesion 6. A lesion in the lateral funiculus of the RIGHT cervical spinal cord affecting the descending tracts would produce which of the following manifestations? a) Weakness of the RIGHT leg b) Complete paralysis of the LEFT leg c) Weakness of the RIGHT arm d) Complete paralysis of the LEFT arm d)LEFT leg 4. Which of the following is a manifestation of an Upper Motor Neuron Lesion? a) Complete paralysis b)Areflexia c) Clonus d)Flaccidity 5. Which of the following is a manifestation of a Lower Motor Neuron Lesion? a) Muscle strength of ⅖ b)Babinski c) Absent cremasteric reflex d)Areflexia 6. Corticobulbar tract fibers pass through which part of the internal capsule? a) Anterior limb b) Posterior limb c) Genu 7. A lesion involving the LEFT Corticobulbar Tract projecting to the facial motor nucleus would produce weakness of which part of the face? a) RIGHT half b)LEFT half c) RIGHT lower half d)LEFT lower half 8. A lesion in the RIGHT hypoglossal nucleus would manifest with which of the following neurologic findings? a) Tongue deviated to the RIGHT, no atrophy b)Tongue deviated to the LEFT, no atrophy c) Tongue deviated to the RIGHT, with atrophy d)Tongue deviated to the LEFT, with atrophy 6)C 5)A 4)D 3) D 2) D 1) B V. FORMATIVE QUIZ 1. The corticospinal tract fibers pass through which part of the internal capsule a) Anterior limb b)Posterior limb c) Genu 2. A patient with a lesion involving the dorsolateral portion of the LEFT sensorimotor cortex will present with which of the following neurologic manifestations? a) Weakness of the RIGHT arm b)Weakness of the LEFT arm c) Weakness of the RIGHT leg d)Weakness of the LEFT leg 8) C 7) C 6) C 5) D 4) C 3) D 2) A 1) B APA CITATION Batch 2025 (2022). Pyramidal and Extrapyramidal Tracts. [Transcription] Calilao, M. (2020). Extrapyramidal Tracts. [Lecture Video] Calilao, M. (2020). Pyramidal Tracts. [Lecture Video] 3. A patient with a lesion of the LEFT lateral funiculus of the lumbar segment of the spinal cord will present with weakness of which of the following? a) RIGHT arm b)LEFT arm c) RIGHT leg ANATOMY LEC | LE6 Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca PAGE 13 of 14 ANATOMY LEC | LE6 Pyramidal and Extrapyramidal Tracts | Melissa C. Calilao, MD, DPPS, DPSA APPENDIX 📋 Table 10. Extrapyramidal tracts arising from the midbrain. Tectospinal & Tectotubular Tract Rubrospinal Tract Origin Superior colliculus Red nucleus (superior colliculus) Course of Cross in dorsal tegmental decussation Cross in ventral tegmental Fibers decussation; lateral funiculus of spinal cord Termination LMN in brainstem and anterior gray Internuncial neurons of all spinal cord horn of spinal cord (upper cervical levels segments) Function Mediate reflex postural movements of Facilitates the activity of flexor muscle head and neck in response to visual groups, functionally similar to the CST; stimuli important indirect pathway 📋 Table 11. Extrapyramidal tracts arising from the pons/medulla. Vestibulospinal Tract (VT) Lateral VT Medial VT Origin Lateral vestibular nucleus Medial vestibular nucleus Course of Fibers Termination Function Descends in anterolateral funiculus of spinal cord, uncrossed Cervical and lumbosacral levels (Lamina VIl & VIII) For maintenance of upright posture and balance (excites extensor motor neurons: neck, back, forelimb, and hindlimb) ANATOMY LEC | LE6 Anterior funiculus of spinal cord, both crossed and uncrossed Cervical and midthoracic (Lamina VII & VIII) Maintains upright posture (excites neck and back motor neurons) Tizon, Tobias, Tolentino A., Tolentino S., Torre, Torrefranca Interstitiospinal Tract Interstitial nucleus of Cajal Uncrossed, forms part of MLF Anterior horn of upper cervical levels of the spinal cord Modulates reflex postural movements in response to visual and vestibular stimuli Reticulospinal Tract (RT) Pontine (Medial) RT Medullary (Lateral) RT Pons (Reticular formation) Medulla (Reticular formation) Anterior funiculus of spinal Lateral funiculus of spinal cord; almost entirely cord; fibers project ipsilateral bilaterally All spinal cord levels (lamina All spinal cord levels VIl & VIII) (Lamina VIl & IX) Facilitatory to extensor Inhibitory to extensor motor motor neurons; influence neurons; influence descending autonomic descending autonomic pathways pathways PAGE 14 of 14