Neuroscience MSP
Problem Set #14
1 a)Describe the three modalities of balance, and where do these modalities integrate?
b) In "Living without a Balancing Mechanism," the patient experiences a shocking fall as he is blindfolded by his facecloth. What is the analogous to this experience in medical approach to vestibular problem?
c) What are the inputs and outputs of the vestibular system?
2. Explain the two paths of vestibulospinal projections that are parallel but different.
3. Why is VOR needed? How does it operate?
4. A 63 year-old patient arrives at your clinic with difficulty focusing his vision on a given target. Upon physical exam, you establish that his second cranial nerve is intact. But when asking him to “follow your finger” caudo-rostrally and laterally you elicit an exaggerated optokinetic nystagmus in both lateral fields. This pathological nystagmus (pathologic because of its severity, not necessarily its presence) is likely to be caused by an anatomical lesion (tumor, cerebro-vascular accident, etc.). Give an anatomically based differential diagnosis of this vestibular malfunction.
5. List the six ways in which nystagmus can be physiologically induced in a normal individual.
6. You are doing a neurology externship at the University of Miami, and a 45-year-old patient with renal cell carcinoma presents with focal neurologic symptoms, highlighted by near-sightedness n the right eye. His internist has established that his cancer has unfortunately metastasized to the apex of his right lung, and is now concerned with metastasis to the brain. Upon physical exam you notice that the right side of his face is very dry (anhidrosis), and that the patient has lid lag (ptosis) in the right eye. When attempting to elicit pupillary light response you notice that pupil responses are intact in left eye (even when shining light in left eye), but you notice that throughout the exam his right pupil is markedly decreased in size (miosis).
Are his miosis and ptosis due to an oculomotor palsy or an Edinger-Westphal nucleus lesion? Given the patient’s history, what type of lesion could describe such findings? Is neuroimaging necessary? How would an oculomotor palsy present? How would a lesion of the Edinger-Westphal nucleus present?
7.a) Name the four most important types of neurons involved in bringing about a saccadic movement of the eye.
b) Describe the function of each of the four types of neurons mentioned above as they relate to the occurrence of a saccade.
8. Match the type of eye movement in the right column with the statement in the left column that best fits the type of eye movement which is named. Use each answer only once.
__orientation a.eye movment velocity is matched to target
velocity.
__pursuit b.involves increased muscular tone
reflexively maintained by the presence of a
target.
__fixation c.response is always saccadic
__exploration d.centrally initiated
9.Discuss what is meant by the phenomenon of corollary discharge.