USMLE Forums banner

1 - 7 of 7 Posts

·
Registered
Joined
·
487 Posts
Discussion Starter · #1 ·


Patient with anisocoria...

A. Diagnostic approach: key questions to ask in the evaluation of the patient with anisocoria
1. The first question to ask: Which eye is abnormal?
2. The second question to ask: Could the abnormal pupil be due to primary ocular disease?
3. If intraocular disease is not present, a neurologic cause of anisocoria is sought.
4. If the mydriatic (dilated) pupil is abnormal - is it an afferent (retina, optic nerve) or efferent (parasympathetic) lesion?
5. If the miotic (constricted) pupil is abnormal - is it a pre-ganglionic or post-ganglionic sympathetic lesion?

B. How do you determine which eye is abnormal?
1. In most patients with anisocoria, only one eye is abnormal.
Less often, both eyes are abnormal. May see with brain trauma (see later) or multiple separate primary ocular disease conditions.

2. How to look for pupil asymmetry
a. Examine from an arm's length away from patient so you can see both eyes simultaneously.
b. Dark room - use retroillumination to view tapetal reflex through pupils.

3. Which is abnormal - the miotic or mydriatic pupil?
a. Examine in light: if the mydriatic pupil fails to constrict, it is abnormal.
b. Examine in the dark: if the miotic pupil fails to dilate, it is abnormal.
 

·
Registered
Joined
·
487 Posts
Discussion Starter · #2 ·
Do this qn

After nearly drowning, an 82-year-old man suffers from severe hypoxia with resulting severe brain edema. This edema leads to raised intracranial pressure. When the pressure exceeds 200 mmHg, the medial temporal lobe begins to be compressed against the tentorium cerebelli. What is typically the first sign of such compression?

A Anisocoria contralateral to compression
B Anisocoria ipsilateral to compression
C Both pupils 5-6 mm and fixed
D External oculomotor ophthalmoplegia
E This condition has no effect on the eyes
 

·
Registered
Joined
·
373 Posts
D External oculomotor ophthalmoplegia

Parasympathetic fibers comprise the outermost fibers of the CN III, so it seems to be the correct answer.
 

·
Registered
Joined
·
12 Posts
i think the answer should be anisocoria of ipsilateral side.
reason: in uncal herniation (medial temporal lobe), parasympathetic effects precede the somatic effects as parasympathetic fibres are on the periphery.
so first is dilated pupil followed by the classical 'down and out' eye features.
 

·
Registered
Joined
·
136 Posts
C

edema cause increase intra cranial pressure, then this should effect both sides of medial temporal lobes leading to
bilateral dilated & fixed pupils :notsure:
 

·
Registered
Joined
·
487 Posts
Discussion Starter · #6 ·
i think the answer should be anisocoria of ipsilateral side.
reason: in uncal herniation (medial temporal lobe), parasympathetic effects precede the somatic effects as parasympathetic fibres are on the periphery.
so first is dilated pupil followed by the classical 'down and out' eye features.
You are most correct.
 

·
Registered
Joined
·
12 Posts
edema cause increase intra cranial pressure, then this should effect both sides of medial temporal lobes leading to
bilateral dilated & fixed pupils :notsure:
ya! also quadriplegia. then it is called kernohan sign. the last stage of raised ict.
 
1 - 7 of 7 Posts
Top