March 31, 2009

Pupillary constriction on light and convergence

A 65-year-old woman is seen for evaluation of dementia. On examination, you note that her left pupil does not react well to light. When she follows your finger with her eyes, as you approach the bridge of her nose, you note the left pupil to constrict equally as well as the right one. [Taken and modified from Question 468,Pre Test USMLE Step 1:Pathophysiology, maurice A. Mufson, Mc Graw-Hill, 2002]

1) What nerve control the Constriction and dilation of the pupils?
2) Name the smooth muscle fibres of Iris and innervation in related to pupillary activity.
3) Explain the condition of the pupillary disorder
4) Name one disease synomous with above condition.
5) What labarotary investigation to confirm above disease.
6) What class of drugs use to treat the pupillary condition
7) At which site the lesion could lie which resulting in the pupillary disorder
8) What other disease associated with this pupillary disorder

Answer scheme

Question 1
- Pnemonic: PCP vs PDS (Pupillary constrict-Parasympathetic, Pupillary Dilate-Sympathetic).
- Cranial nerve III

Question 2
- Spinchter pupillae (Circular constrictor innervated by parasympathetic nervous system)
- Dilator pupillae (Radial dilator innervated by sympathetic nervous system)

Question 3
- Small pupils irregular in shape, which unreact to light but react to accomodation.
- Known as Argyl- Robertson Pupil

Question 4
- Syphilitic infection

Question 5
- Rapid Plasma Reagin, RPR ( a non treponemal antibody test)
- Blood Serology- VDRL, Captia G

Question 6
- Parasympathomimetic drugs ( Carbachol, Phenothiazine)
- Opiates producing miosis.

Question 7
- Midbrain (fibres passing to Edingal Westphal nucleus, posterior commisure or ciliary ganglion)

Question 8
- Midbrain lesion- neoplastic, vascular, inflammatory, demylinative.
- Diabetes
- Alcoholic neuropathy
- Infectious mononucleosis.

Reference: (page 140,141,144, Neurology and Neurosurgery illustrated Fourth Edition, Kenneth W. Lindsay & Ian Bone, Churchill Livingstone, 2004]


But Allah doth call to the Home of Peace: He doth guide whom He pleaseth to a way that is straight. [Q10:25]

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