Clinical Aspects of the Sensory and Motor Pathways

Question 1

lesion of the dorsal roots

Answer 1

• may diminish motor reflexes including muscle tonicity
• involvement of the dorsal roots in the sacral region results in atonic bladder and painless retention of urine
  
  • also occurs with tabes dorsalis

Question 2

if you cut the dorsal root fibers…

Answer 2

get dec tone and dec M spasticity

• cut degree of contracture of M
• input=output–if cut input to reflex arc, you diminish output

Question 3

lesions of primary neurons in conscious sensory pathway

Answer 3

result in ipsilateral lesions

Question 4

unilateral lesions of the posterior columns

Answer 4

-complete unilateral lesions of the posterior columns result in an ipsilateral loss of proprioception, 2 point tactile discrimination and vibratory sensations below to the level of the lesion

Question 5

unilateral lesion of the fasciculus gracilis

Answer 5

• results in ipsilateral loss of proprioception, 2 pt 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

Question 6

unilateral lesion of the fasciculus cuneatus

Answer 6

• results in ipsilateral loss of proprioception, 2 pt tactile discrimination, and vibratory sensations from the upper hand of the body and upper extremity
• partial lesions result in a sensory dermatomal deficit corresponding to the affected region of the fasciculus cuneatus

Question 7

lesion of the lateral corticospinal tract

Answer 7

• results in ipsilateral spastic paralysis, hyperreflexia, hypertonia, Babinski sign, clonus, and disuse atrophy below the level of the lesion
• also occurs with destruction of assoc motor tracts in the lateral funiculus

Question 8

lesion of the lateral reticulospinal tract

Answer 8

• transection of the SC above S2 interrupts the lateral reticulospinal tracts to the sacral autonomic nucleus
• pt is unable to voluntarily cold bladder so experience urinary retention
• after spinal shock, the bladder reflex may return without voluntary control, and pt will have automatic reflex voiding or a reflex bladder

Question 9

unilateral lesion of the lateral spinothalamic tract

Answer 9

-result in contralateral loss of pain and temp sensation 2 sensory dermatomal segments BELOW the level of the lesion

Question 10

lesions of secondary neurons in a conscious sensory pathway

Answer 10

contralateral deficits

Question 11

lesion of the anterior white commissure

Answer 11

-results in bilateral loss of pain and temp sensations to the upper extremities (*yoke like anesthesia)

Question 12

lesions of lower motor neurons in the anterior horn of the SC

Answer 12

• LMN paralysis results from the destruction of motor neurons or the axons of one or more of the cranial or spinal motor nuclei
• LMN paralysis is characterized by flaccid paralysis, areflexia, atonic, atrophy, and fasciculations

Question 13

testing position sense

Answer 13

• with the pt’s eyes closed, the examiner gently flexes and extends the pt’s diner or toe
• pt should be able to indicate whether the digit is bent, straight, unchanged

Question 14

testing vibratory sense

Answer 14

-pt should be able to discern vibrations from activated tuning fork when placed on medial malleolus or MCP joint

Question 15

testing stereognosis and 2 point discrimination

Answer 15

-when placed upon palm or sole, pt should be able to distinguish the 2 blunt tips of open paper clip as being separate

Question 16

poliomyelitis

Answer 16

• affects alpha motor neurons and LMN
• involves the motor neurons of the anterior horns and CN motor nuclei
• initially, there is severe inflammation, vasodilation, edema, macrophagic activity
• then, these neurons die and there is astrocytic gloss
  
  • symptoms may subside and pt may completely recover or result in varying degrees of paresis or paralysis

Question 17

Amyotrophic Lateral Sclerosis (ALS)

Answer 17

• cause is unknown, but may be due to defect in glutamate metabolism
• AKA Lou Gehrig’s Dz
• onset avg is 66 yo
• death due to bulbar paralysis: virtual respiratory centers within an avg of 4 yrs of onset
• most common form involves:
  
  • LMN: anterior horn cells, hypoglossal nucleus, nucleus ambiguus, facial motor nucleus
  • UMN: chronic, progressive degeneration of corticospinal tracts
• ALS leads to LMN paresis and atrophy of the intrinsic Ms of the hands followed by arms and shoulder musculature
  
  • pts may develop dysarthria, dysphagia, and paresis of tongue
  • involvement of corticospinal tract leads to spastic paralysis, hyperreflexia, and Babinski sign
• NO SENSORY DEFICITS

Question 18

anterior horn…

Answer 18

alpha motor neurons, LMN

Question 19

anterior white commissure…

Answer 19

fast pain pathway

Question 20

lateral spinothalamic tract…

Answer 20

pain and temp from contralateral side of body

Question 21

lateral corticospinal tract…

Answer 21

UMN

Question 22

posterior columns…

Answer 22

fasciculus cuneatus (not below T6)
fasciculus gracilis