Egleton - Ascending Spinal Cord Pathways

Question 1

Two Types of Sensation:

Conscious vs Non-Conscious

Answer 1

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)

Question 2

Major pathways for Somatic Sensory perception?

Answer 2

Posterior (dorsal) column–Medial Lemniscal Pathway

Spinothalamic (anterolateral) Pathway

Question 3

Major Function of Posterior Column (Dorsal, Medial Lemniscal Pathway)

Two Sections of Spinal Cord?

Pathway to brain + Decussate?

Chief Functions?

Answer 3

Spinal Cord Sections:

1. Gracile Fasiculus - Lower Body
2. 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

Question 4

Gracile Fasiculus vs Cuneate Fasiculus

Answer 4

Gracile - Carries info from lower body

Cuneate - Carries info from upper body

Border is T6

Cuneate ONLY in UPPER VERTEBRA

Question 5

Clinical: Disturbance of Posterior Column Function?

Answer 5

Most often associated with demyelinating disease such as Multiple Sclerosis

Symptoms: Sensory Ataxia, Romberg’s Sign

Question 6

Major Function of Anterolateral Tract (Spinothalamic)

Sections of Spinal Cord?

Pathway to brain + Decussate?

Chief Functions?

Answer 6

Sections in Spinal Cord:

1. Spinothalamic (Pain and temp)
2. Spinoreticular (Pain emotion and arousal)
3. 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

Question 7

Modality Segregation of Lateral Spinothalamic Tract and Anterior Spinothalamic Tract?

Answer 7

LSTT - Noxious and Thermal Sensations separately

ASTT - Touch

Question 8

What is rough somatotropical organiztion of somatosensory cortex?

Answer 8

Genitals + Legs, Feet = Middle

Hands, Arms = Mid-Lateral

Face = Lateral

Question 9

Clinical: Syringomyelia

Answer 9

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

Question 10

Spinoreticular Tract

Answer 10

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)

Question 11

Spinomesencephalic Tract

Answer 11

Involved in central pain regulation

Question 12

How do the anterolateral tracts interact?

Answer 12

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

Question 13

Spinocerebellar Pathways

Region For:

Posterior Spinocerebellar Tract

Anterior Spinocerebellar Tract

Cuneocerebellar Tract

Answer 13

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

Question 14

Posterior Spinocerebellar Tract

Clarke’s Nucleus

Answer 14

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

Question 15

Cuneocerebellar Tract

Answer 15

Ipsilateral thorax/arm

Travel through lateral cuneate nucleus

Form cuneocerebellar tract

Question 16

What do the Posterior Spinocerebellar and Cuneocerebellar Tract have in common?

Answer 16

Basically same pathways, but Posterior Spinocerebellar = Legs, Cuneocerebellar = Thorax/Arms

Question 17

Anterior Spinocerebellar Tract

How is it different from Posterior Spinocerebellar?

Answer 17

Ipsilateral Leg

Three Main Differences:

1. More complex inputs
2. Decussates at level of spinal cord
3. Different route–enteres superior cerebellar peduncle
   - - -

Main role is MODULATION of SIGNALS

Question 18

Clinical Test: Two Point Discrimination

Answer 18

Measure of Posterior (dorsal) Column-Medial Lemniscal Pathway

Question 19

Clinical Test: Vibration

Answer 19

Test of medial lemniscal pathways

Question 20

Clinical Test: Romberg Test

Answer 20

Cerebellar lesion

Question 21

Clinical: Lesion in Primary Somatosensory Cortext

Answer 21

Deficit contralateral to lesion

Discrimative touch/joint position often affected

Contralteral neglect is a cortical sign

Question 22

Clinical: Lesion in Thalamic Region

Answer 22

Contralateral deficit to lesion, may be more noteiceable in face, hands, and foot

Question 23

Clinical: Lesion to Lateral Pontine or Medulla

Answer 23

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

Question 24

Clinical: Medial Medulla Lesion

Answer 24

Involves medial lemniscus

Causes contralateral loss of vibration and joint position sense

NO FACE = higher medial medulla lesion

Question 25

Clinical: Distal Symmetrical Polyneuropathies

Clinical: Isolated Nerve Injury

Answer 25

DIABETES

Bilateral sensory loss in “glove and stocking” distribution, all modalities

Cause sensory loss in specific territories

Question 26

Clinical: Tabes Dorsalis

Answer 26

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)

Question 27

Clinical: Subacute Combined Degeneration

Answer 27

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

Question 28

Clinical: Demyelinating Disease

Answer 28

Multiple Sclerosis

Difficulty walking up stairs, maybe Lhermitte’s sign

Question 29

Clinical: Lesion of Postcentral Gyrus

Answer 29

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