Egleton - Descending Spinal Cord Pathways Flashcards
Parasympathetic vs Sympathetic
Parasympathetic - Rest & Digest
Originate: Brain Stem and Sacral Cord
Ganglia: Near Target
Long Pre, Short Post
Sympathetic - Fight or Flight
Originate: Thoraco-Lumbar (T1-L3)
Ganglia: Near Spinal Cord
Short Pre, Long Post
Terminus for Autonomic Nervous System fibers?
Intermediolateral Nucleus
Sympathetic: T1-L2
Parasympathetic: S2-S4
Referred Pain
Consequence of convergence of visceral and somatic pain fibers in given dorsal root on same spinothalamic tract.
Area corresponds to dermatome innervated by spinal segment to which the visceral afferents projects.
Corticospinal Tract
Origin?
Role?
“Great Voluntary Motor Pathway”
40% of fibers take origin from Primary Motor Cortex in the Precentral Gyrus
Also contributions from premotor cortex, somatic sensory cortex, parietal lobe, cingulate gyrus, contributions from
Coordinates how muscles move
Primary Motor Cortex
Arrangement?
Somatotropic, similar to motor cortex
Brodmann Area 4, homongulus
Path of Corticospinal Tract?
Forms what?
Decussates?
Starts in Primary Motor Cortex
Descends through the corona radiate and internal capsule to reach brainstem
Continues through the crus of the midbrain and the basilar pons to reach the medulla oblongata
Forms the Pyramid
85% fibers Decussates at Pyramidal Decussation, forms Lateral Corticospinal Tract (remaining form Anterior Corticospinal Tract)
15% Decussate at origin of LMN
Descending Motor Pathways and Motor Neurons:
Upper Motor Neuron (UMN) vs Lower Motor Neuron (LMN)
Upper Motor Neuron: Motor neurons projecting from the Cortex to the Spinal Cord or Brain Stem
Form synapses onto LMN in Anterior Horns of Central Grey in Spinal Cord or Brain Stem
Lower Motor Neuron: Axons project from CNS via Anterior Spinal Roots in Spinal Cord or via Cranial Nerves to muscle cells
Indirect Corticospinal Pathways:
Rubrospinal
Tectospinal
Vestibulospinal
Regulate background activity against which the cortiospinal pathway exerts its influence
Rubrospinal tract
Origin?
Decussates?
Travels Down?
Function?
Origin: Red Nucleus of Brain Stem
Decussates: Ventral Tegmentum
Descends: Lateral Column
Function: Integrates information, coordinates automatic movements (locomotion)
Anterior Grey Horn
Intrinsic muscles of hand and foot?
Diaphragm?
Each motor neuron column in the Anterior Horn supplies muscles having similar functions.
Trunk = Medial
Extensors Anterior to Flexors
Retrodorsolateral Nucleus devoted to hand/foot
Central Nucleus supplies Diaphragm
What is a unique property of corticomotoneuronal fivers of the Lateral Column Spinothalamic Tract?
What can be the result of a lesion in this area?
Fractionation - small groups can be selectively activated
Results in skilled movements
- - -
Damage to corticomotorneural fibers = loss of skilled movement, hard to recover
Types of Motor Neurons:
Alpha vs Gamma
Alpha = Main force generation
Gamma = Regulate Sensitivity
Renshaw Cells
Feedback Cells
Involved in co-contraction of like muscles, and inhibition of their antagonists
Also attenuate alpha motorneuron activity
Excitatory Internuncials
Ia Inhibitory Internuncials
Help recruit additional motor neurons
Antagonist Inactivation – first neurons activated during voluntary movement
UMN Lesion vs LMN Lesion
(not table, just define)
UMN = Lesion in pathway prior to synapse in the anterior horn
LMN = Lesion anywhere between the muscle and the synapse in the anterior horn
LMN Lesion:
Strength?
Muscle Tone?
Stretch Reflex?
Atrophy?
Other Signs?
LMN Lesion:
Strength: Decrease
Muscle Tone: Decrease
Stretch Reflex: Decrease
Atrophy: Severe
Other Signs:
Fasciculation (visible small twitch), Fibrillation (not visible small twitch)
UMN Lesion:
Strength?
Muscle Tone?
Stretch Reflex?
Atrophy?
Other Signs?
UMN Lesion:
Strength: Decrease
Muscle Tone: Increase
Stretch Reflex: Increase
Atrophy: Mild
Other Signs: Clonus, Pathological Reflex (Babinski)
Pathological Sign of LMN Lesion
Flaccid Paralysis
Results from denervation of muscle
Lack of muscle tone, absence of movement (plegia), decreased reflex
Pathological Sign of UMN Lesion
Spasticity (continuous contraction)
Hyperreflexia
Clasp-knife
Clonus
Abnormal Reflex Sign (Babinski)
Abnormal Superficial Flexor Reflexes?
Abdominal Cutaneous Reflex
Cremasteric Reflex (males)
Bulbocavernous Reflex
Anal Wink
Clinical: Unilateral Face, Arm, and Leg Weakness (no associated Somatosensory Defects–pure Motor)
Hemiparesis or Hemiplegia
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Locations Ruled Out:
Cortical - would need whole motor cortex
Muscle/Peripheral Nerve - would have to be a lot
Spinal Cord/Medulla - Face would be spared
Locations Rules In:
Corticospinal / corticobulbar fibers between cortex and medulla (internal capsule, basilar pons, cerebral peduncle)
Lesion Location WRT to Weakness:
Contralateral to weakness
Common Cause:
Blood supply to Internal Capsule (Middle Cerebral Artery, Anterior Choroidal Artery), or Pons (Basilar Artery)
Demyelination or tumor at bold locations
Lesion at Medulla–above / below?
Side affected?
Contralateral = Above
Ipsilateral = Below
Clinical: Unilateral Face, Arm, Leg Weakness (with associated somatorsensory, oculomotor, visual defects)
Hemiparesis or Hemiplegia
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Locations Ruled Out:
Below medulla
Locations Rules In:
Entire primary cortex
Lesion Location WRT to Weakness:
Contralateral to weakness
Common Cause:
Infarct / hemorrhagic stroke, tumor, trauma, herniation
Unilateral Arm and Leg Weakness or Paralysis
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Locations Ruled Out:
Cortical spinal tract below motor cortex and above medulla (no face)
Muscle or peripheral nerve
Spinal cord below C5 (would have some arm sparing)
Locations Rules In:
Arm/Leg area of motor cortex
Cortical Spinal Cord below Medulla and Above C5
Lesion Location WRT to Weakness:
Contralateral if Cortical or Medulla (above decussation)
Ipsilateral if Below
Common Cause:
Infarcts, Multiple Sclerosis, Lateral Trauma / Cervical Spinal Cord Compression
Associated Features:
Cortical may be associated with aphasia
Medial medulla may also lose vibration on side of lesion, tongue contralateral
Unilateral Face and Arm Weakness or Paralysis
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Associated Features?
Locations Ruled Out:
Muscle or Peripheral Nerve
Internal Capsule or Below
Locations Rules In:
Face and Arm areas of Motor Cortex
Lesion Location WRT to Weakness:
Contralateral
Common Cause:
Middle Cerebral artery superior division
Tumors, abcesses
Associated Features:
UMN and dysarthria
Broca’s Aphasia (if dominant hemisphere)
Unilateral Arm Weakness or Paralysis
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Associated Features?
Locations Ruled Out:
Corticospinal tract
Locations Rules In:
Arm area of Motorcortex
Peripheral nerves supplying arms
Lesion Location WRT to Weakness:
Contralateral = motorcortex
Ipsilateral = nerves
Common Cause:
Motor Cortex = Infarct of MCA, tumor
Nerve = Compression Injury, Diabetes
Associated Features:
Motor Cortex = UMN signs
Nerve = LMN signs
Unilateral Leg Weakness or Paralysis
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Associated Features?
Locations Ruled Out:
Corticospinal tract above thoracic cord (no arm)
Locations Rules In:
Motor Cortex leg area
Lateral corticospinal tract below T1
Peripheral Nerve supplying leg
Lesion Location WRT to Weakness:
Motor Cortex = Contralateral
Spinal Cord/Nerve = Ipsilateral
Common Cause:
Motor Cortex = Anterior Cerebral Artery, tumor
Spinal Cord = Unilateral cord trauma, tumor, MS
Nerve = Compression, Diabetes
Associated Features:
Motor Cortex = UMN signs
Spinal Cord = UMN signs, Brown-Sequard
Nerve = LMN signs
Unilateral Face Weakness or Paralysis
Locations Ruled Out?
Locations Rules In?
Lesion Location WRT to Weakness?
Common Cause?
Associated Features?
Locations Ruled Out:
Below Rostral Medulla
Locations Rules In:
Common - CN VII
Uncommon - Lesion in face area, facial nucleus, pons, rostral medulla
Lesion Location WRT to Weakness:
Ipsilateral if CN VII/nucleus, Contra if motor cortex/internal capsule
Common Cause:
CN VII (Bell’s Palsy), Trauma, Surgery
Associated Features:
CN VII - Forehead and orbicularis oculi, hyperacusus, loss of taste, ear pain
Motor Cortex - Forehead spared, tongue weakness
Bilateral Arm Weakness or Paralysis
Locations Ruled Out:
Locations Rules In:
Lesion Location WRT to Weakness:
Common Cause:
Associated Features:
Locations Ruled Out:
Corticospinal Tracts (no face, legs)
Locations Rules In:
Medial fibers of both lateral corticospinal tracts
Bilateral cervical spine ventral horn cells
Lesion Location WRT to Weakness:
Medial (bilateral)
Common Cause:
Central Cord Syndrome (Syringomyelia, cord tumor)
Anterior Cord Syndrom (ant. Art. infarct, trauma)
Peripheral Nerve (carpel tunnel, disc herniation)
Associated Features:
Central cord syndroms or anterior cord syndrome, peripheral nerve disorders affecting both arms
Bilateral Leg Weakness or Paralysis
Locations Ruled Out:
Locations Rules In:
Lesion Location WRT to Weakness:
Common Cause:
Associated Features:
Locations Ruled Out:
Corticospinal tract above T1 (no face, arms)
Locations Rules In:
Motor Cortex (both leg areas)
Lateral Corticospinal Tracts below T1
Cauda Equina Syndrome
Lesion Location WRT to Weakness:
Medial (bilateral)
Common Cause:
Motor Cortex = Parasagittal Meningioma, Cerebral Palsy
Spinal Cord (Common) = Tumor, Trauma, Myelitis, Epidural abscess
Bilateral Peripheral nerve = Cauda Equina Sundrom, Guillian Barre, Lambert-Eaton, diabetes
Associated Features:
Bilateral Arm and Leg Weakness or Paralysis
Locations Ruled Out:
Locations Rules In:
Lesion Location WRT to Weakness:
Common Cause:
Associated Features:
Locations Ruled Out:
Between motor cortex and medulla
Spinal cored below C5 (arms would be spared)
Locations Rules In:
Motor Cortex (bilateral arm and leg)
Corticospinal Tracts between medulla and C5 (bilateral lesions)
Peripheral Nerve and Muscle disorders of all four limps
Lesion Location WRT to Weakness:
Medial (bilateral)
Common Cause:
Motor Cortex = Watershed infarcts, anterior cerebral palsy
Upper Cervical / Lower Medulla = Tumor, Trauma, Infarct, MS
Nerve/Muscle = Lots
Associated Features:
Motor Cortex = UMN, cognitive dysfunction, aphasia
Upper Cervical Cord = UMN, sensory dysfunction, respiratory issues, trigeminal issues
Lower Medullary = UMN, headache, tongue weakness, hiccups, abnormal eye movements
Peripheral Nerve = LMN
Generalized Weakness and Paralysis
Locations Ruled Out:
Locations Rules In:
Lesion Location WRT to Weakness:
Common Cause:
Associated Features:
Locations Ruled Out:
Small focal or unilateral lesions
Lower medulla or spinal cord (face would be spared)
Locations Rules In:
Motor cortex (bilateral)
Corticospinal tracts between corona radiata and pons (bilateral)
Lesion Location WRT to Weakness:
Common Cause:
Global cerebral anoxia, Pontine infarct (Locked In Syndrome), Advanced ALS, Guillain Barre, Myasynthia, Botulism
Associated Features:
Motor / Corticospinal = UMN
Nerve = LMN
Clinical: Spinal Muscular Atrophy
Congenital degeneration of cells of Anterior Horns of Spinal Cord
Mutation of SMN1 Gene
Diffuse proximal muscle weakness (more in lower limbs)
Decrease deeo tendon reflex
Clinical: Amyotrophic Lateral Sclerosis (ALS, Lou Gehrig’s Disease)
Heterogeneous group of neurodegenerative diseases of both UMN and LMN
Progressive loss of Anterior Horn Cells, Corticobulbar, Corticospinal tract, and Betz neurons in motor cortex and neurons of te cranial nerve motor nuclei
Small muscles will waste first, weight loss, speech, respiration difficult
Clinical: Occlusion of Anterior Spinal Artery
Spares dorsal columns and Lissauer tract
Can be caused by Aortic Aneurysm Repair
UMN below lesion
LMN at level of lesion
Loss of temp/pain sensation below lesion
Clinical: Tabes Dorsalis
Caused by Syphilis
Demyelination of dorsal columns and roots
Progressive sensory ataxia, impaired proprioception
Romberg Sign
Clinical: Syringomyelia
Syrinx expans and damages the Anterior White Commissure of Spinothalamic Tract
Bilateral loss of pain and temperature in cape like pattern
Clinical: Vitamin B12 Deficiency
Demyelination of Spinocerebellar tracts, Lateral corticospinal tracts, dorsal columns
Symptoms: Ataxic Gate, Paresthesia, Impaired position and vibration sense
Clinical: Cauda Equina Syndrome
Compression of spinal roots L2 and below
Cause: Disc herniation
Absense knee/ankle reflex, loss of bladder and anal sphincter reflex
Saddle anesthesia
Clinical: Poliomyelitis
Caused by Polio virus
Destruction of cells in Anterior Horn
LMN signs
Clinical: Brown-Sequard (prob on exam..)
Hemisection of Spinal Cord
Ipsilateral loss of all sensation at level of lesion
Ipsilateral LMN sign at level of lesion
Ipsilateral UMN sign below level of lesion
Ipsilateral loss of pripriocepition, vibration, light tourch below lesion
Contralateral loss of pain, temp, and non-discrimative touch below lesion
