Abstract 265: A Curious Case Of Acute Binocular Diplopia, Ischemic Stroke Of The Interstitial Nucleus Of Cajal
Authors: Ahmed Hamza M. , Al‐Awwad Ahmad 
Published: March 2024

Introduction
The nuclei in the periaqueductal gray of the midbrain are critical structures that coordinate and control vertical and torsional gaze, as well as crucial components of the vestibulo‐occular reflex. These structures are so fine that they may be missed on routine imaging however, they represent distinct localizations for the neurological exam, with lesions of these structures being important clinical considerations.
The Interstitial Nucleus of Cajal (inC) coordinates signals from the saccadic burst neurons in the rostral interstitial nucleus of the medial longitudinal fasiculus (riMLF), vestibular projections (utricular and semicircular canal pathways from the vestibular nuclei via the MLF), and descending pursuit fibers, the paired interstitial nuclei of Cajal act as neural integrators for vertical gaze and torsion.
These nuclei lie adjacent but dorsal and caudal to the riMLF, For upgaze, fibers from the inC cross via the posterior commissure, then connect to the contralateral superior rectus and inferior oblique subnuclei. For downgaze, fibers travel across the posterior commissure, then innervate the contralateral inferior rectus subnucleus and fourth nerve nucleus. Blood supply is derived from the terminal branches of the basilar artery. Lesions of these interstitial nuclei and their tracts may produce vertical and torsional gaze‐holding deficits such as impairments in the vertical vestibulo‐occular reflex, hypertropia, counter‐rolling of the eyes, superior oblique palsy, and see‐saw and torsional nystagmus.

Methods
Case report and review of literature

Results
45‐year‐old, right‐handed woman with history of turner syndrome, anemia, nephrolithiasis, horseshoe kidney, premature ovarian failure on hormone replacement therapy (HRT), suspected adrenal mass of undetermined significant, and degenerative disk disease presented to the emergency department with complaints of acute binocular diplopia and dizziness clarified to be sensation of the ground/objects bobbing in visual field. Neurological exam significant for left hypertropia and exotropia in primary gaze, equal in right/left gaze and right/left head tilt, as well as large amplitude medium frequency (see‐saw) nystagmus characterized by upbeat nystagmus with intorsion on the right, and downbeat nystagmus with extorsion left. Visual fields were intact to finger count with binocular diplopia and oscillopsia noted in primary gaze. CT head and CT angiogram of the head and neck were unrevealing. Initial MRI brain negative for diffusion restriction but with flair hyperintensity in periaqueductal gray prompting repeat MRI brain without contrast with thin slices through the brainstem with showed infarct in periaqueductal gray within the region of the interstitial nuclei, with stroke etiology undetermined at the time of presentation but suspicion of small vessel disease vs hypercoagulability given propensity for thrombophilia in Turner syndrome and patient being on HRT. Full dose aspirin and high intensity statin therapy was initiated given presentation out of tPA window, and hypercoagulability workup initiated prior to discharge.

Conclusion
Acute ischemic stroke and lesions of the interstitial nuclei in the periaqueductal gray are important, under recognized considerations for the evaluation of binocular diplopia, that may represent an opportunity for thrombolytic administration if providers had a higher index of suspicion. Hypercoagulability and Turner syndrome are also unique qualifiers, underscoring a nuanced approach to determination of stroke diagnosis and etiology in cases of isolated ocular symptomology.