Localization of ANS/HT Disorders Flashcards
Which regions, if lesioned, will produce horner’s syndrome?
Which region regulates heat dissipation?
Either the posterior or medial hypothalamus can produce Horner’s syndrome.
The anterior region is involved in heat dissipation–lesioning there causes hyperthermia.
What diseases can cause dysregulation of the suprachiasmatic nucleus? What does this cause?
Where do pyrogens act to increase temperature set point?
What can cause overeating via downregulation of medial (ventromedial) hypothalamic function?
Alzheimer’s disease is known to cause dysregulation here, resulting in insomnia. Shiftwork can also “throw off” the SCN.
The anterior nucleus is involved in heat dissipation, pyrogens act here to induce fever.
Prader-Willi (genetic) or craniopharyngioma can produce these effects.
Describe the course of SNS outflow to the level of T1.
How may these fibers then reach the eye?
Fibers originate in the PVN, and travel laterally through the brainstem and spinal cord (interomediolateral column).
Exit at the T1 level, then ascension in the chain ganglia to the superior cervical ganglion. From there, fibers track along the internal carotid artery to reach the eye (dilator pupillae).
Name 3 conditions that can cause disruption of SNS outflow, especially to the eyes.
- Pancoast tumor affecting the brachial plexus (including T1).
- Cavernous sinus disruption (eg thrombus, pituitary adenoma)
- ICA dissection (but generally not aneurysms).
What is horner’s syndrome? What are its symptoms?
What is “anisocoria”?
Disruption of SNS outflow to the ipsilateral eye, causing miosis, ptosis, and anhidrosis.
Uneven pupil size. Typically a product of Horner’s syndrome.
Describe how light-flash can test parasympathetic circuitry.
What does it mean if there is a direct but not consensual constriciton in response to this test?
In a light-flash test, afferents from the optic nerve reach the edinger-westphal nuclei bilaterally. This is a parasympathetic nucleus, which triggers miosis in either eye (innervation of sphincter pupillae).
This could indicate a lesion of one pretectal/EW nucleus, but could also indicate a CN III lesion on the other side.
Summarize the effects of SNS and PNS innervation to the bladder.
Overstimulation of which one will cause urinary retention?
SNS relaxes the detrusor and activates the internal urinary sphincter (no voiding).
PNS activates the detrusor and relaxes the IUS (micturition).
Urinary retention is generally caused by overactive SNS.
Explain how bladder incontinence could be caused either by PNS or SNS overactivity.
How will they differ on exam?
PNS activation causes excessive voiding (spastic bladder or weak sphincter). It is treated with anti-cholinergics.
SNS activation causes retention, which may progress to incontinence as a result of overflow (flaccid bladder or spastic sphincter). It is treated with anti-adrenergics.
Incontinence due to SNS activity will yield a full bladder, clearly apparent following catheterization.
What visual disturbances might a craniopharyngioma cause?
Bitemporal hemianopia (impinge on the optic chiasm; lose both temporal field inputs).
What exam findings usually accompany ICA dissections?
Horner’s syndrome as well as various cortical signs due to interrupted supply to the circle of willis (eg neglect, numbness).
