Somatosensory Tracts 2 Flashcards
what is the collective system for the pathways that are responsible for relaying pain, temperature and non-discriminative touch?
the anterolateral system
what is the largest tract that makes up the anterolateral system?
the spinothalamic tract
where do the pain and temperature afferent fibers enter the spinal cord?
the lateral division of the posterior root entry zone (posterolateral fasciculus)
after entry, some fibers ascend/descend 1-2 levels in what?
the posterolateral (Lissauer) tract
where do the afferent fibers target after entry into the spinal cord?
they target 2nd order neurons in the posterior horn in superficial laminae I and II
what is the immediate next step of the second order neuron?
to immediately extend through the posterior horn, cross in the anterior white commissure and then move over to the contralateral side of the spinal cord and join the ALS
What is the somatotopic set up of the ALS?
axons from lower levels are found posterolaterally and more rostral levels are added in an anteromedial sequence
where do 2nd order neurons go after reaching the contralateral ALS?
they ascend up to the VPL nucleus of the thalamus
what kind of fibers are found in the indirect spinothalamic pathway?
spinoreticular fibers
what is the main purpose of the spinoreticular pathway?
it contributes to the perception of dull pain and moderates behavioral and motivational changes associated with pain
where do the 2nd order neurons travel to after joining the contralateral ALS in the spinoreticular pathway (indirect spinothalamic pathway)?
3rd order neurons in the reticular formation
where does the blood supply of the ALS originate from?
the arterial vasocorona and via the sulcal branches of the anterior spinal artery
What does occlusion of the blood supply of the ALS result in?
patchy loss of nociceptive, thermal, and touch over the contralateral side of the body, 2 SPINAL SEGMENTS BELOW the lesion
what does a complete spinal cord injury result in?
bilateral, total loss of all motor and sensory function at/ below the level of injury
what does an incomplete spinal cord injury result in?
some function remains below the primary level of the injury
what does an anterior cord syndrome result in?
injury to the motor and pain/temperature pathways in the anterior spinal cord. Patient’s still have proprioception and sensation
what does a central cord syndrome result in?
damage to the center of the cord/ anterior white commissure. causes loss of pain/temp pathways, with deficits relative to the size of the lesion
what is Brown-Sequard Syndrome?
it is a combination of sensory and motor deficits due to damage to the ALS, PCML, and CST pathways
what are the results/symptoms of brown-sequard syndrome?
contralateral deficits: loss of nociceptive, thermal sensation (ALS) approximately 2 segments below the level of lesion; ipsilateral deficits: loss of discriminative tactile, vibratory, and position sense (PCML) at/below the lesion, paralysis of the trunk and extremity (CST)
what is the diagnosis of cystic cavitation of central regions of the spinal cord?
Syringomyelia
What is the initial damage of a syringomyelia?
to ALS fibers in the anterior commissure
How do deficits present for cases of syringomyelia?
cape-like pattern- loss of pain and temperature bilaterally over the arms and shoulders; weakness atrophy, and fasciculations of muscles of the hands
What is the trigeminal nuclei responsible for pain, temperature, and non-discriminative touch?
spinal trigeminal nucleus
what is the range of the spinal trigeminal nucleus?
obex–> C2/C3
what are the three divisions of the spinal trigeminal nucleus?
pars caudalis, pars oralis, pars interpolaris
where do the primary afferent fibers for the trigeminal come in at?
the levels of the mid pons
what happens after the primary afferent fibers enter?
they descend down to the spinal trigeminal nucleus
Once the primary afferent descend and enter into the spinal nucleus, what happens nect?
the second order neurons cross midline within the medulla
after crossing within the medulla, what do the second order neurons ascend as?
anterior trigeminothalamic tract
where do the second order neurons target after crossing within the medulla?
they target the contralateral VPM nuclei of the thalamus
where is the opthalmic dermatome located on the spinal trigeminal nucleus?
anteriorly
where is the mandibular dermatome located on the spinal trigeminal nucleus?
posteriorly
where do the fibers from right around the mouth terminate on the spinal trigeminl nucleus?
rostrally–> near the obex
where do the fibers of the midcheek terminate on the spinal trigeminal nucleus?
the middle segments
where do the fibers of the lateral edges of the face terminate on the spinal trigeminal nucleus?
the caudal regions down to C2/C3
damage to the spinal trigeminal tract can be described as what type of sensory loss?
onion-peel sensory loss
a more caudal lesion of the spinal trigeminal nucleus would result in what?
it spares the oral region, but it affects the posterior and lateral boundaries of the face
a more rostral lesion (into the brain stem) of the spinal trigeminal nucleus would result in what?
sensory loss that is increasingly anterior and converges on the mouth
what happens when you get a lateral medullary syndrome?
there is an occlusion of the posterior inferior cerebellar artery or branches of the posterior inferior cerebellar artery
what happens when you get lateral pontine syndrome?
there is an occlusion of the long circumferential branches of the basilar artery and/or branches of anterior inferior cerebellar artery or superior cerebellar artery
what is the reticular formation?
it is a region in the pons
What is the vascular supply of the lateral medulla?
PICA (posterior inferior cerebellar artery
what would an occlusion of PICA result in?
contralateral loss of pain and thermal sensation
what is the vascular supply of the lateral pons?
long circumferential branches of basilar artery and/or branches of anterior inferior cerebellar artery or superior cerebellar artery
what would an occlusion of the long circumferential branches of the basilar artery and/or branches of the anterior inferior cerebellar artery or superior cerebellar artery result in?
contralateral loss of pain and thermal sensation
what is alternating trigeminal hemiplegia?
unilateral destruction of the trigeminal nerve and CST in the pons
what would you expect to see with alternating trigeminal hemiplegia?
ipsilateral trigeminal anesthesia and paralysis as well as contralateral spastic hemiplegia
