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Show A Macro Dilemma Demonstrations of the anterior chiasmal syndrome and Wilbrand's Knee Created by Drs. Ariel Axelbaum1 and Nurhan Torun 1,2 Departments of Neurology (1) and Ophthalmology (2) Beth Israel Deaconess Medical Center, Boston, MA Harvard Medical School, Boston, MA Case 1: History • 75 year-old woman who noticed progressive worsening vision in her left eye starting ~2 years prior to examination with no visual changes in her right eye. • PMH: hypertension • Ocular history: unremarkable • Referred to neuro-ophthalmology after MRI brain did not revealed an etiology for her symptoms. MRI brain without contrast prior to referral MRI read as normal Axial and sagittal T1 without contrast Case 1: Neuro-ophthalmology Examination • • • • • • BCVA 20/25 OD, 20/400+1 OS. No improvement with pinhole Relative afferent pupillary defect OS Color vision 16.5/17 OD, unable to see plates OS Extraocular motility was full Confrontation fields were full to finger counting OU Slit lamp exam showed diffuse pallor OS with normal appearing disc OD Humphrey Visual Fields • Significant superior and temporal field loss OS with a small amount of temporal field loss OD • Optical coherence tomography (OCT) of the optic nerves demonstrated definite nerve fiber layer losses OS and questionable thinning of optic nerve OD OS OD MRI brain WITH contrast Axial T1 without contrast Axial T1 with contrast Sagittal T1 with contrast MRI with contrast shows a sellar mass that extends from sella/suprasellar region. Retrospective review of initial MRI • Looking back, lesion was evident on original MRI, but did not enhance without contrast. • Initial imaging should have included contrast as well as orbital cuts to fully evaluate for causes of her vision loss. Axial T2 Case 2- History • 59 year-old male referred for vision loss in the left eye. First noticed by the patient incidentally 3 months prior to visit when he covered his right eye. • PMH: DM and HTN • Ocular history: unremarkable • Medication: Enalapril, metoprolol, metformin, gemfibrozil, and Viagra Case 2- Examination • BCVA 20/20 OD and count fingers at 1 ft OS. No improvement with pinhole. • Relative afferent pupillary defect OS • Extraocular motility was full • Confrontation fields full to finger counting OD; full to finger count in the nasal quadrants OS, hand motion only in the temporal quadrants • Slit lamp exam showed diffuse pallor OS and possible temporal pallor OD Humphrey Visual Fields OS Dense temporal hemianopia with central and inferonasal defects OS. Superotemporal defect OD. OD MRI brain with and without contrast MRI brain with and without contrast shows a large homogenously enhancing sellar and suprasellar mass abutting the anterior chiasm. Patient was taken for surgical resection. Coronal T1 without contrast Coronal T1 with contrast Visual Field Comparison- before/after resection Prior to resection OS After resection OD Question 1: Why did these sellar masses not present with bitemporal hemianopia? The answer is contained in the next slides! There is variation in chiasmal anatomy Incidence1: 5% 78% 17% These differences contribute to varying symptoms from sellar masses. 1. Gulsen S, Dinc AH, Unal M, Cantürk N, Altinors N. Characterization of the anatomic location of the pituitary stalk and its relationship to the dorsum sellae, tuberculum sellae and chiasmatic cistern. J Korean Neurosurg Soc. 2010;47(3):169-173. doi:10.3340/jkns.2010.47.3.169 Question 2: In case 2, the mass is primarily compressing the medial left optic nerve. Why is there a contralateral superotemporal quadrantanopia? OS OD Pre-thalamic visual pathways Note that the inferonasal fibers cross anterior to the superonasal fibers. These fibers are referred to as Wilbrand's knee. Anterior chiasmal syndromes 1. 2. Lesion 1 is slightly more anterior than lesion 2, thus sparing the decussating fibers. Teaching Points • MR contrast is usually needed to visualize and characterize intracranial masses. • Chiasmal anatomy varies, prefixed and postfixed chiasms are seen in ~5% and 17% of patients respectively. • Nasal fibers decussate at the chiasm with inferonasal fibers crossing anteriorly to superonasal fibers. • Masses can present with varying symptoms based on the location of the mass, the anatomy of the optic pathways, and the relation between the two. |
