Case Study 
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History: Trigeminal Nerve Sheath Tumor
A ten year old Paint gelding presented to Animal Imaging for an MRI of the brain.  In January of 2009, the horse was treated for a refractory ulcer on the left eye.  The ulcer did not respond to treatment.  Other symptoms noted included mild unilateral facial sweating, marked unilateral atrophy of the masticatory muscles, decreased palpebral reflex and corneal reflexes, as well as retraction of the eye.
  Trigeminal Nerve Sheath Tumor                                                   MR Findings: 
An MRI exam of the brain revealed a large mass associated with the left trigeminal nerve.  The mass originates at the level of the origin of the trigeminal nerve at the brain stem and extends rostrally along the floor of the calvarium to the level of the mid brain reaching its widest diameter of 3.4cm.  It extends rostrally to involve both ophthalmic and maxillary branches of the trigeminal nerve.  The mass causes a mass effect with a resulting shift of the mid brain towards the right.   
Impressions and Recommendations:
The large mass is most consistent with a trigeminal nerve sheath tumor.  This extensive mass does carry a poor prognosis.  The left eye would likely need to be enucleated.  Potential treatment could involve focused radiation with a linear accelerator.  This may shrink the mass to some extent, but would likely not be curative.  The mass effect could lead to increased CNS signs including vestibular involvement. 
Animal Imaging 
Animal Imaging is a veterinary referral diagnostic center in Irving offering MRI, Scintigraphy, Radiology, Fluoroscopy and Ultrasound for companion animals and equine patients. 

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Jake Hersman, DVM            Robert Cole, DVM, DACVR           Susan Willenbrock
Managing Partner                 Imaging Director                           Office Manager
(972) 869-2180                     (972) 869-2180                             (972) 869-2180