E-Pearl of the Week: Junctional Scotoma of Traquair

February 14, 2011

Brought to you by the Resident and Fellow Section of the journal Neurology®.

February 14, 2011

Quick Quiz: When does a unilateral optic nerve lesion cause visual loss from both eyes?

Answer: When it involves Wilbrand's knee!

Lesions at the junction of the optic nerve and optic chiasm may produce a characteristic visual field defect. Ipsilateral optic nerve involvement results in a central scotoma. The fibers from the inferonasal retina of the contralateral eye may loop anteriorly for a short distance in the ipsilateral optic nerve (known as Wilbrand's knee). Involvement of Wilbrand's knee produces a supero-temporal scotoma in the contralateral eye.

The combination of ipsilateral central scotoma and contralateral supero-temporal scotoma is known as a junctional scotoma. The cause should be assumed to be a compressive lesion at the junction of the optic nerve and chiasm until proven otherwise. Caveat: some have questioned whether the phenomenon of Wilbrand's knee is an artifact of anatomical preparation or eye enculeation, however.

References

1. Miller NR, Newman NJ. Topical diagnosis of acquired optic nerve disorders. In: Miller NR, Newman NJ, editors. Walsh and Hoyt's Clinical Neuro-ophthalmology 6th ed. Baltimore: Lippincott Williams & Wilkins; 2005: 228-229.
2. Kirton A, Shroff M, Pontigon AM, deVeber G. Risk factors and presentations of periventricular venous infarction vs. arterial presumed perinatal ischemic stroke. Arch Neurol 2010; 67:842-848.
3. Lee JH, Tobias S, Kwon JT, Sade B, Kosmorsky G. Wilbrand's knee: does it exist? Surg Neurol. 2006; 66: 11-17.

Suresh Subramaniam, MD, MSc, Chief Neurology Resident University of Calgary

Disclosure: Dr. Subramaniam has nothing to disclose.

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