Egleton - Ascending Spinal Cord Pathways Flashcards
Two Types of Sensation:
Conscious vs Non-Conscious
Conscious
- Perceived at cerebral cortex
- Two types: Exteroceptive (external sensation, touch, pressure, heat, cold, pain, vision, hearing), Proprioceptive (body sense)
Non-Conscious
- Routed to cerebellum
- Two types: Proprioception, Interoception (visceral reflexes)
Major pathways for Somatic Sensory perception?
Posterior (dorsal) column–Medial Lemniscal Pathway
Spinothalamic (anterolateral) Pathway
Major Function of Posterior Column (Dorsal, Medial Lemniscal Pathway)
Two Sections of Spinal Cord?
Pathway to brain + Decussate?
Chief Functions?
Spinal Cord Sections:
- Gracile Fasiculus - Lower Body
- Cuneate Fasiculus - Upper Body (T6 >)
Pathway to Brian:
Move along Gracile/Cuneate to Medulla where they will decussate
Move to pons, midbrain, thalamus, then somatosensory cortex
Chief Functions:
Conscious Proprioception and Discriminative Touch
Gracile Fasiculus vs Cuneate Fasiculus
Gracile - Carries info from lower body
Cuneate - Carries info from upper body
Border is T6
Cuneate ONLY in UPPER VERTEBRA
Clinical: Disturbance of Posterior Column Function?
Most often associated with demyelinating disease such as Multiple Sclerosis
Symptoms: Sensory Ataxia, Romberg’s Sign
Major Function of Anterolateral Tract (Spinothalamic)
Sections of Spinal Cord?
Pathway to brain + Decussate?
Chief Functions?
Sections in Spinal Cord:
- Spinothalamic (Pain and temp)
- Spinoreticular (Pain emotion and arousal)
- Spinomesencephalic (Central modulus of pain)
Pathway to Brain:
Some axon collateral ascend/descend for muliple segments before entering central grey–permit’s coodinated response; decussates at ORIGIN of insertion
Anterior Spinothalamic Tract/Lateral Spinothalamic Tract merge in brain stem to form spinal lemniscus, joined by trigeminal from head
30 neurons project from thalamus to the somatosensory cortex
Modality Segregation of Lateral Spinothalamic Tract and Anterior Spinothalamic Tract?
LSTT - Noxious and Thermal Sensations separately
ASTT - Touch
What is rough somatotropical organiztion of somatosensory cortex?
Genitals + Legs, Feet = Middle
Hands, Arms = Mid-Lateral
Face = Lateral
Clinical: Syringomyelia
Stem: “Injury in car crash”
Characterized by syrinx (fusiform cyst) in or beside central canal in cervical region
Symptoms: Dissociated sensory loss–loss of pain and thermal stimuli; ulcers can get developed on fingers and joint capsules can get stretched
Spinoreticular Tract
Involved in arousing the cerebral cortex to maintain waking state
Also reports to limbic cortex of the anterio cingulate gyrus aout the nature of a stimulus (pleasure vs pain)
Spinomesencephalic Tract
Involved in central pain regulation
How do the anterolateral tracts interact?
Spinothalmic - Tells you something sharp is touching your foot
Spinothalamic intralaminar projections/Spinoreticular Tract - Cause you to “feel” pain, probably aversive
Spinomesencephalic - modulates pain, eventually feels better
Spinocerebellar Pathways
Region For:
Posterior Spinocerebellar Tract
Anterior Spinocerebellar Tract
Cuneocerebellar Tract
Fiber tracts from spinal cord to cerebellum–provide feedback from the body, regulate limbs on SAME SIDE
Posterior Spinocerebellar Tract - Leg
Anterior Spinocerebellar Tract - Leg
Cuneocerebellar Tract - Arm
Posterior Spinocerebellar Tract
Clarke’s Nucleus
Ipsilateral leg + ipsilateral trunk
Fibers pass through the inferior cerebellar peduncle to the medial cerebellum
Clarke’s Nucleus - neurons of medial part of lamina VII; do not exist caudal to L2–neither does spinocerebral tract
Cuneocerebellar Tract
Ipsilateral thorax/arm
Travel through lateral cuneate nucleus
Form cuneocerebellar tract
What do the Posterior Spinocerebellar and Cuneocerebellar Tract have in common?
Basically same pathways, but Posterior Spinocerebellar = Legs, Cuneocerebellar = Thorax/Arms
Anterior Spinocerebellar Tract
How is it different from Posterior Spinocerebellar?
Ipsilateral Leg
Three Main Differences:
- More complex inputs
- Decussates at level of spinal cord
- Different route–enteres superior cerebellar peduncle
- - -
Main role is MODULATION of SIGNALS
Clinical Test: Two Point Discrimination
Measure of Posterior (dorsal) Column-Medial Lemniscal Pathway
Clinical Test: Vibration
Test of medial lemniscal pathways
Clinical Test: Romberg Test
Cerebellar lesion
Clinical: Lesion in Primary Somatosensory Cortext
Deficit contralateral to lesion
Discrimative touch/joint position often affected
Contralteral neglect is a cortical sign
Clinical: Lesion in Thalamic Region
Contralateral deficit to lesion, may be more noteiceable in face, hands, and foot
Clinical: Lesion to Lateral Pontine or Medulla
Contralateral anterolateral and ipsilateral trigeminal pathway
Loss of pain and temperature sensation in the body opposite the lesion
Loss of pain and temperature sensation in the face on the same side of the lesion
Clinical: Medial Medulla Lesion
Involves medial lemniscus
Causes contralateral loss of vibration and joint position sense
NO FACE = higher medial medulla lesion
Clinical: Distal Symmetrical Polyneuropathies
Clinical: Isolated Nerve Injury
DIABETES
Bilateral sensory loss in “glove and stocking” distribution, all modalities
Cause sensory loss in specific territories
Clinical: Tabes Dorsalis
Caused by Syphilis
Degeneration of the dorsal columns of the spinal cord
Bilteral loss of fine touch, vibration, and conscious proprioception
May have Romberh/Lhermitte’s Sign (electrical like shock)
Clinical: Subacute Combined Degeneration
Deficiency in B12 – VEGANS
Chronic demyelination and loss of acons in the dorsal and dorsolateral columns, more posterior
May product dementia
Loss of proprioception, discriminative touch, vibration, ataxia, coordination, spastic weakness or paralysis
Clinical: Demyelinating Disease
Multiple Sclerosis
Difficulty walking up stairs, maybe Lhermitte’s sign
Clinical: Lesion of Postcentral Gyrus
Usually hit multiple modalities
Larger lesions result in loss of fine touch, proprioception, in body part represented
Parathesia may be present
Difficulty localizing pain
Astereognosis: Loss of size/shape/texture discrimination
Agraphesthesia: Inability to reognize letters and numbers drawn on palm of hand
