Ascending Spinal Cord Pathways Flashcards
What is Exteroceptive sensation?
Sensations from the external world
Where are conscious sensations perceived in the brain?
The level of the cerebral cortex
Where are non-conscious sensations perceived?
They aren’t perceived
Routed to the cerebellum
What are the two major pathways involved in somatic sensory perception?
Posterior column-medial lemniscal pathway
Spinothalamic (anterolateral) pathway
The medial portion of the spinal column, gracile fasiculus, carries information from where?
Legs and lower trunk
The cuneate fasiculus carries information from where?
Upper trunk, Arm, neck, and occiput
T6 and up
What is the chief function of the posterior column-medial lemniscal pathway?
Conscious proprioception and discriminative touch
What is disturbance of posterior column function associated with?
Demyelinating diseases such as MS
Sensory ataxia
Romberg’s sign
What are the three tracts in the anterolateral pathway?
Spinothalamic - pain and temperature
Spinoreticular - pain emotion/arousal
Spinomesencephalic - central modulation of pain
Where does the secondary afferent decussate in the anterolateral pathway?
At the level of its origin via the anterior commissure
Describe modality segregation in the spinothalamic tract.
Lateral ST - mediates noxious and thermal sensations separately
Anterior ST - mediates touch
What is Syringomyelia?
Disorder associated with some kind of trauma
Syrinx (fusiform cyst) in or beside the central canal, typically in the cervical region
Initial symptoms arise from obliteration of spinothalamic fibers decussating in the white commissure
What is the clinical presentation of syringomyelia?
Dissociated sensory loss
Sensitivity lost to pain and temp., retained to touch
Ulcers arising from painless cuts and burns
Disorganized joints due to loss of warning from stretched joint capsules
What is the spinoreticular tract?
Arises from Laminae VI-VII
Invovled in arousing the cerebral cortect i.e. induce or maintain the waking state
Assigns some emotional context to sensation
What is the spinomesencephalic tract?
Arises in laminae I and V
Involved in central pain regulation
What are the three spinocerebellar pathways?
Posterior SC tract
Anterior SC tract
Cuneocerebellar tract
Where does the Posterior SC tract originate?
Clarke’s nucleus
Travels through nucleus gracilis until about L2
What peduncle does the Posterior SC tract enter the cerebellum through?
Inferior
Origin, body part, peduncle for the cuneocerebellar tract?
Origin: Lateral cuneate nucleus
Body part: Trunk, upper extremity
Inferior peduncle
Where does the anterior spinocerebellar tract originate, body part represented, peduncle, cross?
Origin: Spinal border cells
Body part: Trunk, lower extremity
Crossing: Once in cord, again in cerebellum
Peduncle: Superior
What pathway does two-point discrimination and vibration test?
Posterior column-medial lemniscal pathway
What does contralateral neglect indicate?
A lesion in the cortex
What is most often affected due to a lesion in the somatosensory cortex?
Discriminative touch and joint position sense
Contralateral to lesion
Where are the deficits due to a lateral pontine or medullary lesion?
Contralateral anterolateral pathway
Ipsilateral trigeminal pathway
What deficits are associated with lateral pontine or medullary lesions?
Loss of pain and temperature sensation in the body contralateral
” “ in the face ipsilateral to the lesion
What deficits occur with a medial medullary lesion?
Contralateral loss of vibration and joint position sense
What deficits are associated with distal symmetrical polyneuropathies?
Bilateral sensory loss in a “glove and stocking” distribution, all modalities
What is Tabes Dorsalis?
Inflammatory invovlement of the dorsal roots results in degeneration of the dorsal columns of the spinal cord
Caused by tertiary syphilis
What are the clinical presentations of Tabes Dorsalis?
Bilateral loss of fine touch, vibration and conscious proprioception
Romberg and/or Lhermitte’s signs may be present as well, depending on location of lesions
What is subacute combined degeneration?
Deficiency in Vitamin B12 intake or metabolism
Chronic demyelination and loss of axons in the dorsal and dorsolateral columns; more posterior columns than lateral corticospinal tract
May also involve deep white matter of the hemispheres to produce dementia
What is the clinical presentation of subacute combined degeneration?
Loss of proprioception, discriminative touch, vibration, ataxia, and spastic weakness or paralysis
What is the clinical presentation of Multiple Sclerosis?
Lack of proprioceptive input - causing falling
Lhermitte’s sign if cervical areas are involved
Loss of discriminative touch, conscious proprioception and vibration
Constellation of symptoms
What deficits will occur with large lesions to the postcentral gyrus?
Sensory loss involving a number of submodalities
Body part correlates with position of the lesion on the gyrus
What deficits occur with a small lesion to the postcentral gyrus?
Loss of two-point discrimination
Difficulty in localizing painful stimulation precisely (but not loss of pain sensation)
Body part affected correlates to position of the lesion on the gyrus
What is astereognosis?
Loss of size/shape/texture discrimination
What is agraphesthesia?
The inability to recognize letters and numbers drawn on the palm of the hand
