Sensory Systems: Proprioception Pathways Flashcards
Generally Speaking, how do spinal cord lesions present at the following locations?
- Dorsal Roots
- Posterior Columns
- Lateral Funiculus
- Anterior Funiculus
1. Dorsal Roots - Ipsilateral sensory dermatomal anesthesia; Ipsilateral diminished muscle tone/reflex, if reflex arc to muscle is impaired
2. Posterior Columns - Ipsilateral loss of proprioceptive/2-point discrimination below level of lesion
3. Lateral Funiculus - Ipsilateral UMN paralysis/paresis below level of lesion
4. Anterior Funiculus - Contralateral loss of pain and temperature below the level of lesion; Ipsilateral lower motor paralysis at the level of lesion; IF the lesion is bilateral, volitional control of bladder and bowel
1.
2.
- B
- C
- B
- C
What is his “favorite” stem for this exam?
“These findings indicate involvement of which of the following…”
What are some of the common clinical presentations for central lesions?
- Hemianalgesia and/or Hemianesthesia of Limb(s)
- Spastic paralysis/paresis or hemiplegia of Limb(s)
- Paraplegia or quadriplegia
- Supranuclear Facial Palsey
- Systemic Disorders/Diseases
- Visual Field Blindness
- Bilateral Deficits (occassionally)
How do the spinal nerves relate to the vertebral levels?
C-Spine - Spinal Nerve comes out ABOVE the vertebrae
T-Spine & L-Spine - Spinal nerve comes out BELOW the vertebrae
Differetiate between “Crude” and “Precise” proprioceptive pathways.
Crude: Says you are in contract with something
Precise: Say EXACTLY which object you are in contact with
**** Involves the CORTEX!
- A
- E
- B
- C
- B
Describe the Posterior Column-Medial Lemniscal System.
SENSORY from Arms and Legs!
***Some primary fibers synapse directly upon alpha motor neurons as part of a myotatic reflex circuit
*** Secondary Neurons that cross over are known as Internal Arcuate Fibers before they ascend as the Medial Lemniscus.
*** Secondary Neurons terminate on the Ventral Posterior Lateral (VPL) nucleus of the thalamus
Describe the following Unilateral Lesions of the Posterior Column/Medial Lemniscus Pathway:
- Unilateral Lesion of Fasciculus Gracilis
- Unilateral Lesion of Fasciculus Cuneatus
- Unilateral Lesion of the Medial Meniscus
1. Unilateral Lesion of Fasciculus Gracilis - result in an ipsilateral loss of proprioception, 2- point tactile discrimination and vibratory sensations from the lower half of the body and lower extremity. Partial lesions result in a sensory dermatomal deficit corresponding to the affected region of the fasciculus gracilis.
2. Unilateral Lesion of Fasciculus Cuneatus - result in an ipsilateral loss of proprioception, 2-point tactile discrimination and vibratory sensations from the upper half of the body and upper extremity. Partial lesions result in a sensory dermatomal deficit corresponding to the affected region of the fasciculus cuneatus
3. Unilateral Lesion of the Medial Meniscus - result in a loss of proprioception, two-point tactile discrimination and vibratory sensations on the opposite side of the body and limbs
Describe the Ventral Spinothalamic Pathway?
**** CRUDE TACTILE PATHWAY
Enter the DORSAL root and will ascend 6-10 segment levels (short ascending fibers)
Primary neurons will terminate in the Nucleus Proprius
Secondary neurons decussate in the ANTERIOR WHITE COMMISSURE and ascends as the Anterior Spinothalamic Tract (ASTT); Meets up with the Lateral Spinothalamic Tract to form the SPINAL LEMNISCUS (starts in the medulla); Terminates in the Ventral Posterolateral Nucleus in the medulla
Tertiary neurons will project to the Postcentral Gyrus
What are the various Unconscious Sensory Tracts that are going to head to the Cerebellum?
1. Cuneocerebellar Tract - Precise information from Upper Extremity
*** Primary axons from the C1-7 levels ascend in the lateral aspect of the posterior column, and terminate in the accessory cuneate nucleus
2. Dorsal Spinocerebellar Tract - Precise information from individual muscles from the Lower Extermity and Lower half of the body
3. Ventral Spinocerebellar Tract - Gross postural and general proprioception from the Lower Extremity and Lower Half of the body
Describe the various Lesions:
- Unilateral lesions of the Ventral Spinothalamic Tract (VSTT)
- Unilateral lesion of the Spinal Lemniscus
1. Unilateral lesions of the Ventral Spinothalamic Tract (VSTT) - May be difficult to lose crude touch sensations, because fibers ascend in both the posterior (primary fibers) and anterolateral funiculi (secondary fibers). This separation of information provides the system with a degree of bilaterality. Also, deficits associated with discrete lesions of the VSTT may be “masked” if the posterior column/medial lemniscal system is intact
2. Unilateral lesion of the Spinal Lemniscus - results in a contralateral hemianalgesia and thermal hemianesthesia. The loss of passive touch may be masked by the intact posterior column/medial lemniscal system
