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Thursday, March 29, 2007

Tabes Dorsalis

  • This is a manifestation of tertiary (late) syphilis called neurosyphilis
    • caused by infection with treponema pallidum, a spirochete
    • tertiary syphilis also turns the vasa vasora (blood vessels that supply other blood vessels, eg aortic root) into a bunch of granulomas →:
      • Aortic regurgitation – know how to recognize!
        • Diastolic decrescendo murmur heard best along the left sternal border
      • Aneurysm of the ascending aorta
  • Note that tabes dorsalis only affects the dorsal horns.
  • This patient had a positive (+ve) Rhomberg's sign
    • Rhobmerg's sign
      • Patient's balance is fine with his eyes open
        • Visual input supplies spatial awareness/proprioception
      • Upon closing his eyes the pt sways
        • loss of proprioception from dorsal column

(If patient is swaying with eyes open and closed, this is likely a lesion in the cerebellum or vestibular system (eg. CN VIII) and would NOT qualify as a +ve Rhomberg's sign)

  • Can you guess the level from which this spinal cord section was taken
A) C1
B) C4
C) T4
D) L4
E) S1

Answer posted on 4/2/07

Note the lateral horns (sometimes called intermediolateral cell column):
(I have circled the right one and have drawn an arrow to the left one)
This area of white matter contains preganglionic sympathetics which arise from the hypothalamus and will synapse onto a postganglionic sympathetic fiber in the paravertebral (aka chain) ganglion. Question for you... would the neurotransmitter used here be
a) norepinephrine (Norepi)
b) epinephrine (Epi)
c) acetylcholine (ACh)
d) glycine (Gly)
e) glutamate (Glu)
f) seratonin (5-HT)

Answer is c) Ach
Remember, all preganglionic autonomic fibers use ACh
Epinephrine is released from the adrenal medulla when preganglionic sympathetic fibers release ACh onto it.

Now, back to the level of the spinal cord:
Since we are talking about sympathetic (aka thoraco-lumbar) outflow, you should know right away that this slide must therefore have been sliced from somewhere between T1-L2.
Knowing this would have gotten you the right answer to my question.

If the question writer is out for your blood he may ask you to distinguish between 2 choices within the range of the lateral horn. Notice the shape of the above section. Now compare it to an upper lumbar section. See the difference? The lumbar section has only one dorsal column and it is just a lot more round. That "just a lot more round" part (I bet) is enough to differentiate for purposes of the exam. But feel free to knock yourself out, I know I did.

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