Spinal Cord
The posterior nerve roots enter the spinal column at a site called the? The anterior nerve roots exit the spinal column at a site called the?
Posterior(sensory) enter at Posterior Lateral Sulcus Anterior (motor) leave at Anterior Lateral Sulcus
UMN cell bodies are located ? LMN cell bodies are located?
UMN: cell bodies located in cerebral cortex (corticospinal tract) and brainstem LMN: cell bodies located in ventral horn or brainstem motor nuclei (facial nerve motor nucleus)
http://www.usmleforum.com/files/forum/2009/1/441653.php
http://www.usmleforum.com/files/forum/2009/1/441653.php
A 29-year-old man comes to a local hospital with duodenal peptic ulcer and complains of cramping epigastric pain. Which of the following structures harbors the cell bodies of abdominal pain fibers? (A) Lateral horn of the spinal cord (B) Anterior horn of the spinal cord (C) Dorsal root ganglion (D) Sympathetic chain ganglion (E) Celiac ganglion
(C) Dorsal root ganglion Cell bodies of the abdominal pain fibers are located in the dorsal root ganglion. The lateral horn of the spinal cord contains cell bodies of sympathetic preganglionic nerve fibers; the anterior horn contains cell bodies of general somatic efferent (GSE) fibers. The sympathetic chain ganglion contains cell bodies of sympathetic postganglionic fibers, which supply blood vessels, sweat glands, and hair follicles. The celiac ganglion contains cell bodies of sympathetic postganglionic fibers, which supply the visceral organs such as stomach and intestine.
A 17-year-old boy was involved in a gang fight, and a stab wound severed the white rami communicantes at the level of his sixth thoracic vertebra. This injury would result in degeneration of nerve cell bodies in which of the following structures? (A) Dorsal root ganglion and anterior horn of the spinal cord (B) Sympathetic chain ganglion and dorsal root ganglion (C) Sympathetic chain ganglion and posterior horn of the spinal cord (D) Dorsal root ganglion and lateral horn of the spinal cord (E) Anterior and lateral horns of the spinal cord
(D) Dorsal root ganglion and lateral horn of the spinal cord The white rami communicantes contain preganglionic sympathetic general visceral efferent (GVE) fibers and general visceral afferent (GVA) fibers whose cell bodies are located in the lateral horn of the spinal cord and the dorsal root ganglia. The sympathetic chain ganglion contains cell bodies of the postganglionic sympathetic nerve fibers. The anterior horn of the spinal cord contains cell bodies of the GSE fibers. The dorsal root ganglion contains cell bodies of GSA and GVA fibers.
Ventral Spinothalamic Tract
*Carries discriminative/crude touch and pressure The Anterior Spinothalamic Tract is organized very similarly to the Lateral Spinothalamic pathway ; however, it is less clinically-emphasized since the Dorsal Column Medial Lemniscus pathway is more important for touch sensation. If the Anterior Spinothalamic pathway is lesioned, touch sensation will only be minimally affected, as long as the dorsal column remains intact. The Lissauer Tract is exclusive to the Lateral Spinothalamic Tract
Anterior Spinothalamic Tract
*Carries pain and temperature *-1*: ADelta/C fibers have free nerve endings in the periphery, their cell bodies in the DRG, and the the central processes enter the Dorsal horn and ascend or descend a few spinal cord levels in the Lissauer tract before entering the gray matter *Synapse primarily in superficial laminae (I and II) and in the nucleus proprius (laminae III and IV). -2*:Cross the midline within the spinal cord in the anterior white commissure and ascends as the anterior spinothalamic tract and terminate in the VPL of the thalamus -3*: From VPL, fibers project to the somatosensory cortex via the internal capsule *
Dorsal Column/Medial Lemniscus Pathway
*Carries sensory information for discriminative touch, joint position/proprioception, pressure, vibration -1*: Afferent fibers of various peripheral sensory receptors have their cell bodies in the DRG The axons of these fibers enter the dorsal horn and ascend as the fasciculus gracilis or cuneatus and synapse with second order neurons in the medulla (nucleus gracilis/cuneatus) -2*: The fibers from the nucleus gracilis/cuneatus cross the midline as internal arcuate fibers and then ascend the brainstem in the medial lemniscus and terminate in the VPL of the thalamus -3*: From VPL, fibers project to the somatosensory cortex via the internal capsule
Anterior Spinal Artery Syndrome
*Most common clinical presentation of a spinal cord infarction * * * **Preservation of fine touch, proprioception, and vibration (spares dorsal column and lissauer tract) *Initially areflexia (spinal shock) followed by spasticity *Usually occurs after surgery to repair thoracic or thoracoabdominal aortic aneurysm
Blood supply to the spinal cord
*Single Anterior Spinal Artery: supplies anterior 2/3 of spinal cord *Paired Posterior Spinal Artery: supplies posterior 1/3 of spinal cord *Artery of Adamkiewicz: Supplies the lower 2/3 of the spinal cord via the anterior spinal artery (below T8) https://pdfs.semanticscholar.org/3b37/493f4c50cb1006b79804857fa650d0193c6e.pdf
Identifying a section of the Spinal Cord
*Two dorsal columns: T5 and above *Lateral horn present: T1-L2 *Large ventral horn: C5-T1; L2-S2 *Cervical sections have a thin dorsal horn and a flattened ventral horn *Thoracic sections have a thin dorsal and ventral horn *Moving rostrally, there is more white matter
Label following sections of the Spinal Cord
A) Cervical B) Lumbar C) Thoracic D) Sacral
A 76-year-old woman complains that her right hand feels a bit numb and "clumsy." When she reaches for a glass of water, for example, she sometimes knocks it over. Which one of the following arteries is most likely to be occluded by an embolus in this scenario? A. Branches of the right posterior spinal artery at the level of the cervical spinal cord. B. Branches of the right anterior spinal artery at the level of the cervical spinal cord. C. Branches of the right posterior inferior cerebellar artery at the level of the rostral medulla. D. Branches of the left vertebral artery at the level of the caudal medulla. E. Right paramedian branches of the basilar artery at the level of the caudal pons.
A. Branches of the right posterior spinal artery at the level of the cervical spinal cord. Branches of the right posterior spinal artery supply the posterior column tracts (i.e., fasciculus gracilis and fasciculus cuneatus), which carry fine touch, proprioception, and vibration sense. Information for the hand related to these modalities is carried by the fasciculus cuneatus. A lesion of the branches of the posterior spinal artery supplying the fasciculus cuneatus at the level of the cervical spinal cord could result in loss of discriminative touch and proprioception, which, in turn, could result in the feelings of numbness and clumsiness.
White matter in the spinal cord is divided into three columns fasciculi, what are they?
Anterior Posterior Lateral
Which Spinal tracts would be affected by infarction of the Anterior Spinal Artery? Posterior Spinal Artery?
Anterior Spinal Artery -Corticospinal(loss of motor fxn) -Spinothalamic(loss of pain, temperature, pressure) -Lateral/intermedial horn(autonomic dysfxn: loss of bladder/bowel control, sexual dysfxn Posterior Spinal Artery -Dorsal column (loss of proprioception. vibration sense, two point discrimination) *note that the deficits are all bilateral and occur below the level of the lesion
Describe the somatotopic organization of the Ventral Horn
Anterior: Extensors Posterior: Flexors Lateral: Distal muscles Medial: Proximal muscles
A 58 year old male in the Intensive care ward exhibited little voluntary control of urinary or fecal activity following a transplant procedure of his left kidney. In addition, physical examination revealed widespread paralysis of his lower limbs. These functions were essentially normal prior to admission to the hospital. The most likely cause of this patient's problems is which of the following? A) Injury to the left vertebral artery B) Injury of the great radicular artery (of Adamkiewicz) C) Ligation of the posterior spinal artery D) Transection of the conal segment of the spinal cord E) Division of the thoracic sympathetic chain
B) Injury of the great radicular artery (of Adamkiewicz) The (great radicular) artery of Adamkiewicz is important for blood supply to anterior and posterior spinal arteries. The location of this artery should be noted during surgery because damage to it can result in dire consequences, including loss of all sensation and voluntary movement inferior and at the level ofthe injury. Injury to the left vertebral artery would not be likely due its superior location to the surgical site. Ligation of the posterior spinal artery would not occur because of its protected location inside the spinal column. Transection of the conus medullaris of the spinal cord would not occur as this structure is located at L1, L2 levels and is, again, protected inside the spinal column. Division of the thoracic sympathetic chain would not be likely as the symptoms described include limb paralysis, which would not be a consequence of sympathetic disruption.
Which ascending spinal pathway (tract) carries the same sensory information as the spinothalamic tracts and the dorsal-column/medial-lemniscal system, but from the face nasal cavity, oral cavity, and teeth? A) spinotectal B) trigeminothalamic C) spinoolivary
B) trigeminothalamic
Which statement is true of sensory information on discriminative touch, vibration, and proprioception that enters the spinal cord? A. It ascends ipsilaterally until reaching the pons. B. It crosses the midline in the caudal medulla. C. It has second-order neurons in the Clarke column. D. It synapses in the posterior horn before ascending. E. It ultimately synapses in the ipsilateral primary and association sensory cortices
B. It crosses the midline in the caudal medulla. Cell bodies of the first order neurons are in the spinal ganglia. Information enters the spinal cord and ascends without synapsing to terminate in the nuclei gracilis and cuneatus in the caudal medulla. From there, second-order neurons cross the midline as the internal arcuate fibers and ascend to the thalamus.
A 25-year-old male race car driver is admitted to the emergency department after a severe car crash. Radiographic studies reveal damage to the tip of the transverse process of the third cervical vertebra, with a significantly large pulsating hematoma. What artery is the most likely to have been damaged? A. Anterior spinal artery B. Vertebral artery C. Ascending cervical artery D. Deep cervical artery E. Posterior spinal arteries
B.. Vertebral artery The vertebral arteries run through the transverse foramina of cervical vertebrae C6 through C1 and are therefore most closely associated with injury to the transverse processes. The anterior spinal artery is located anteriorly along the spinal cord and is not directly associated with the vertebrae. The ascending cervical artery is a very small branch from the thyrocervical trunk of the subclavian artery, running on the anterior aspect of the vertebrae. The deep cervical artery arises from the costocervical trunk is also a very small artery and courses along the posterior aspect of the cervical vertebrae. The posterior spinal arteries are adherent to the posterior aspect of the spinal cord.
Which of the following ascending sensory pathways (tracts) contains secondary neurons that cross at the level of the medulla? A) lateral spinothalamic B) anterior spinothalamic C) dorsal-column/medial-lemniscal system D) posterior spinocerebellar
C) dorsal-column/medial-lemniscal system
A patient presents with selective loss of pain and temperature sensations to both hands. Other sensory modalities and voluntary motor activity are intact. What is the most likely cause of this problem? A. A lesion to the left and right anterolateral white columns at the level of the cervical spinal cord. B. A lesion to the left and right anterolateral white columns at the level of the caudal medulla. C. A lesion around the central canal at the cervical level of the spinal cord, extending into the white matter anteriorly. D. A lesion to both left and right branches of the anterior spinal artery at the level of the cervical spinal cord. E. A lesion to both left and right branches of the anterior spinal artery at the level of the caudal medulla
C. A lesion around the central canal at the cervical level of the spinal cord, extending into the white matter anteriorly. This is a case of syringomyelia, a central cavitation of the spinal cord beginning around the central canal. It can result from inflammation and other causes. The cavitation can then extend further into the central gray matter, affecting the anterior gray horns, and/or can extend into the white matter. In this case, the cavitation has extended into the white matter anterior to the central canal, disrupting the crossing fibers of the left and right anterolateral or spinothalamic tracts. At the cervical level of the cord, specifically C7-C8, this would result in loss of pain and temperature sensations to the hands. The other choices all would involve a fairly large bilateral lesion, which would present with additional symptoms.
A young woman develops signs and symptoms of multiple sclerosis. Both of her lower limbs are weak, she has bilateral Babinski signs, and her muscle stretch reflexes are hyperactive. Her physician concludes that she has a lesion of upper motor neurons. The woman's hyperactive muscle stretch reflexes result from overactivity of muscle spindles. Excessive stimulation of which of the following neurons that innervate the polar regions of muscle spindles is most likely responsible for the womanâ's hyperactive muscle stretch reflexes? A. Alpha motor neurons B. Class C dorsal root afferent fibers C. Gamma motor neurons D. Ia dorsal root afferent fibers E. Ib dorsal root afferent fibers
C. Gamma motor neurons Gamma motor neurons innervate the polar regions of the muscle spindle, and when overstimulated in individuals with an upper motor neuron lesion, cause the central part of the spindle to be stretched, resulting in a lowering of the threshold for activation of the muscle spindle, and hyperactive muscle stretch reflexes. Alpha motor neurons (choice A) are the lower motor neurons that innervate extrafusal muscles fibers, and when stimulated cause extrafusal fibers to contract. Class C dorsal root afferent fibers (choice B) are unmyelinated sensory fibers that convey nociceptive information into the spinal cord. Ia dorsal root afferent fibers (choice D) innervate the central regions of muscle spindles, and form the afferent limb of the muscle stretch reflex. Ib dorsal root afferent fibers (choice E) innervate Golgi tendon organs which when excessively stimulated make skeletal muscles relax.
A 70-year-old woman with atrial fibrillation who is not taking anticoagulation medication "throws" an embolus and develops sudden weakness in her legs. She also has some associated pain in the legs and back. Which of the following would be expected on back and neurologic examination? A. Absence of the Babinski reflex B. Intact pain and temperature sensation over both lower legs C. Intact vibration and proprioception in the feet D. Spasticity would be present on inspection of the lower legs E. Tenderness over the spinal process at the vertebral level of the embolus
C. Intact vibration and proprioception in the feet Vibration and proprioception are spared in anterior spinal artery thrombosis, because they are in the posterior columns and not located in the anterior two thirds of the spinal cord that becomes infarcted.
Which region of the spinal cord contains more white matter? The cervical or caudal regions?
Cervical
Which ascending spinal pathway (tract) carries the sensations of two-point discrimination, proprioception, pressure and vibration? A) lateral spinothalamic B) posterior spinocerebellar C) anterior spinothalamic D) dorsal-column/medial-lemniscal system E) spinotectal
D) dorsal-column/medial-lemniscal system
A lesion in branches of the anterior spinal artery that supply the medial aspect of the lateral white column of the spinal cord is most likely to cause deficits in A. Discriminative touch and proprioception on the ipsilateral side. B. Pain and temperature sensations on the contralateral side. C. Pain and temperature sensations on the ipsilateral side. D. Voluntary movement on the ipsilateral side. E. Coordinated movements of the lower limbs
D. Voluntary movement on the ipsilateral side The lateral corticospinal tract, which mediates voluntary motor activity, travels in the lateral column of the spinal cord. It carries motor information from the cerebral cortex to the anterior horn cells in the spinal cord.
Compare the location of the cell bodies in spinal nerves of the Dorsal vs Ventral root
Dorsal root: Cell bodies are located in the Dorsal root ganglion (pseudounipolar cells) Ventral root: Cell bodies are located in the Ventral horn
Which of the following statements about the spinocerebellar tracts is correct? A. Proprioceptive and exteroceptive information from the lower limb is carried to the cerebellum in the cuneocerebellar tract. B. The rostral spinocerebellar tract integrates information from the lower limb with descending input. C. The Clarke nucleus plays an important role in integrating proprioceptive information from the upper and lower limbs. D. The anterior spinocerebellar tracts project directly to the side of the cerebellum ipsilateral to the original peripheral input. E. Spinal border cells convey information to the cerebellum about the postural stability of the lower limb.
E. Spinal border cells convey information to the cerebellum about the postural stability of the lower limb. Spinal border cells are unique cells in the anterior horn of the spinal cord. They receive input from lower limb muscles as well as input from modulating descending tracts to the lower motor neurons and from flexor refl ex arcs in the spinal cord, and can feed this integrated information back to the cerebellum. The sum of the input to the spinal border cells gives information to the cerebellum about the postural stability of the lower limb.
A patient swaying with their eyes closed is a sign of ____________(cerebellar/dorsal column) damage A patient swaying with their eyes open is a sign of ____________(cerebellar/dorsal column) damage
Eyes closed: Dorsal column damage (loss of proprioception) Eyes open: Cerebellar damage
A positive Romberg test is a sign of Cerebellar dysfunction T/F?
F! Romberg's test is not a test of cerebellar function, as it is commonly misconstrued. Patients with cerebellar ataxia will, generally, be unable to balance even with the eyes open; therefore, the test cannot proceed beyond the first step and no patient with cerebellar ataxia can correctly be described as Romberg's positive. Rather, Romberg's test is a test of the proprioceptive receptors and pathways function.
The posterior column is subdivided above T6 into two fasciculi. What are they called and what type of information do they carry?
Fasciculus Gracilis and Fasciculus Cuneatus Gracilis = medial = carry discriminative touch and proprioception from ipsilateral lower body (below T6) Cuneatus = lateral = concerning discriminative touch and proprioception from the ipsilateral upper body (above T6)
A 23 year old man has had progressive weakness and atrophy of the intrinsic muscles of the left hand during the past 3 months. The most likely cause is damage to which of the following labeled sites in cross section of the spinal cord shown? A) B) C) D) E) F) G) H) I) J)
G) Progressive weakness and atrophy of intrinsic muscles of hand = sign of LMN damage LMN neurons have their cell bodies in the anterior horn. The intrinsic hand muscles would be represented by the lateral anterior horn while more proximal muscles would be represented by the medial anterior horn (F) *Remember that degeneration of intrinsic hand muscles is often the first sign of ALS
Inside the spinal cord, _____________ (gray/white) matter is located centrally and is shaped like a butterfly
Gray matter
The Lateral Spinothalamic Tract carries _______________ information The Anterior Spinothalamic Tract carries _______________ information
Lateral: Pain, temperature Anterior: Crude touch, pressure
The gray matter can be subdivided into 10 distinct layers which are called? How are they distributed?
Rexed Laminae (I-X) Layers 1-6 make up the posterior horn Layers 7-9 make up the anterior horn Layer 10 surrounds the central canal
Sensory information enters the spinal cord through the __________(anterior/posterior) roots Motor information enters the spinal cord through the __________(anterior/posterior) roots
Sensory: Posterior Motor: Anterior
The fasciculus gracilis is found at all spinal cord levels while the fasciculus cuneatus is only found in C1-T6 T/F?
T!
A lesion of the Lateral spinothalamic tract causes loss of pain and temperature on the contralateral side of the body T/F?
T! Because fibers carrying pain and temperature travel up or down a few levels before synapsing in the posterior horn and cross the midline within the spinal cord, a lesion of the spinothalamic tract causes a loss of pain and temperature sensation on the side of the body contralateral to the injury, beginning a few levels below or above the level of the injury
Fasciculus Gracilis vs Fasciculus Cuneatus
T6 down?
ASCENDING
TRACTS
Which part of the spinal cord gray matter contains the cell bodies of preganglionic parasympathetic and sympathetic neurons?
The lateral horn Preganglionic Parasympathetic visceral motor cell bodies in S2-S4 Preganglionic Sympathetic visceral motor cell bodies in T1-L2
What is the watershed area of the spinal cord?
The midthoracic spinal cord has been demonstrated to be the most poorly vascularized region of the spinal cord with an inconsistent arterial supply at T4 or T5
What is a watershed area?
Watershed area refers to regions of the body that receive dual blood supply from the most distal branches of two large arteries. During times of blockage of one of the arteries that supply the watershed area, such as in atherosclerosis, these regions are spared from ischemia by virtue of their dual supply. However, during times of systemic hypoperfusion, such as in DIC, Heart failure, or systemic hypotension, these regions are particularly vulnerable to ischemia by virtue of the fact that they are supplied by the most distal branches of their arteries, and thus the least likely to receive sufficient blood.
A 69-year-old woman was admitted to a local hospital after she reported that she couldn't move her legs. Neurologic examination indicated that not only did she lose motor functions in both of her legs but that she could not detect any sensation in either leg when probed with a safety pin. However, she was aware of sensation in both legs when the neurologist applied tactile stimulation to them. It was concluded that the patient suffered damage to the: a. Anterior half of both sides of the spinal cord at the lumbar level b. Posterior half of both sides of the spinal cord at the lumbar level c. Region surrounding the central canal of the lumbar cord d. Left half of the cervical cord e. Dorsal roots of the lower thoracic cord, bilaterally
a. Anterior half of both sides of the spinal cord at the lumbar level
