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Acquired IV th Cranial Nerve Palsy related to a small lesion of the Ivth nerve (presumed s chwannoma ). Rabih Hage , MD Valérie Biousse , MD. Clinical examination. New onset binocular oblique diplopia Right hypertropia in primary gaze Worse with right head tilt
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Acquired IVth Cranial Nerve Palsy related to a small lesion of the Ivth nerve (presumed schwannoma) RabihHage, MD ValérieBiousse, MD
Clinical examination • New onsetbinocular oblique diplopia • Right hypertropia in primary gaze • Worsewithright head tilt • Worse in left gaze • No improvementwhenlyingdown • Small vertical fusion amplitudes • No head tilt on oldphotographs • Consistent withan acquiredright fourthcranial nerve (CN IV) palsy
T1-weighted axial brain MRI Figure 1a T1- weighted axial brain MRI at the level of the inferiorcolliculi
T1-weighted axial brain MRI Figure 1b Magnification of the brainstem
Course of CN IV IV Figure 1c CN IV crosses the midline, circlesanteriorlyaround the brainstem and runsforwardtowards the eye in the subarachnoidspace.
T1-weighted axial brain MRI(without contrast) Figure 2 The brainMRI withoutcontrastisunremarkable. Because of itssmalldiameter. CN IV isnot routinelyvisualized.
T1-weighted axial brain MRI(with contrast) Figure 3 There isfocalenhancementalong the course of the right CN IV, suggesting a small mass on the right CN IV
T1-weighted coronal brain MRI(without and with contrast) Figure 4a Figure 4b 4a: The brainMRI withoutcontrastisunremarkable (the arrow shows the lesionseen on the MRI withcontrast) 4b: There isfocal enhancement of CN IV (yellowarrow)
Final Diagnosis • IVth cranial nerve focal lesion suggesting a mass on the cranial nerve itself. The radiologic appearance suggests a IVth nerve schwannoma. • The patient’s diplopia was treated symptomatically and repeat MRIs over the course of 5 years have not shown any enlargement of the lesion.