Questions:

1. When the etiology of Horner syndrome is not known at the initial neuro-ophthalmologic examination, but sufficient information is obtained to allow targeted imaging, how often is an etiology discovered?
   a. In about 90%
   b. In about 60%
   c. In about 30%
   d. In about 10%

2. When the etiology of Horner syndrome is not known at the initial neuro-ophthalmologic examination, and sufficient information is not obtained to allow targeted imaging, how often is an etiology discovered?
   a. In about 90%
   b. In about 60%
   c. In about 30%
   d. In about 10%

3. What are the two most common causes of Horner syndrome when the cause is not known at the time of presentation and clinical information is sufficient to permit a inferred targeted imaging evaluation?
   a. Apical lung malignancy
   b. Carotid artery dissection
   c. Cavernous sinus lesion
   d. Thyroid malignancy

_______________________________________________

Correct Answers:
1. b. In about 60%
2. d. In about 10%
3. b. Carotid artery dissection & c. Cavernous sinus lesion

Explanation¹: 

Background: The yield of imaging in Horner syndrome has been explored only in children. This study evaluates the yield of imaging in adults.

Methods: This was a retrospective cohort study of 52 patients with Horner syndrome examined in 2 neuro-ophthalmology hospital clinics. Patients were divided into 3 groups according to the ability to determine the etiology at the time of the first neuro-ophthalmology consultation: group I, etiology of Horner syndrome known at the initial neuro-ophthalmologic examination; group II, etiology of Horner syndrome not known at the initial neuro-ophthalmologic examination, but sufficient information obtained to allow targeted imaging; and
group III, etiology of Horner syndrome not known at the initial neuro-ophthalmologic examination, and sufficient information not obtained to allow targeted imaging. The yield of investigation and the frequency of the different etiologies were evaluated.

Results: In 32 (62%) patients, the etiology was already known at the initial neuro-ophthalmologic examination (group I). The most prevalent etiology was surgical trauma. In 11 (21%) patients, a targeted imaging workup was possible, revealing an etiology in 7 patients (7/11=64%  group II). Carotid dissection and cavernous sinus mass were the most common etiologies. In 9 (17%) patients, a nontargeted imaging evaluation was necessary, revealing an etiology in only 1 patient, who had a previously undetected thyroid malignancy (1/9=11% group III).

Conclusions: The etiology of Horner syndrome is usually known at the time of initial presentation to a neuro-ophthalmologist. When the etiology is not known and clinical information permits a targeted imaging evaluation, an etiology can usually be determined, most commonly a cervical carotid artery dissection or a cavernous sinus mass. When the etiology is not known and clinical information is insufficient to allow a targeted imaging evaluation, an etiology is rarely discovered. Even so, nontargeted imaging is warranted because life threatening lesions, such as thyroid malignancies, may rarely be detected.

Reference:
1. Diagnostic Value of Imaging in Horner Syndrome in Adults. Almog et al: J Neuro-Ophthalmol 2010; 30;1:7-11

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