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cranialnerves [2026/05/26 18:16] – scottcranialnerves [2026/06/05 14:34] (current) – [The Vestibulocochlear / Facial Nerves] scott
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 ====The Optic Nerves==== ====The Optic Nerves====
  
-The optic nerves are paired nerves extending from the optic chiasm, just rostral to the pituitary gland, toward the eyes in an oblique dorsal plane. The optic nerves are not as commonly affected as the other cranial nerves, but do require more special imaging when it is necessary to assess them. To best assess the optic nerves, consider a few things: The nerves are small, surrounded by CSF, cushioned in fat, well vascularized, and take a tortuous and oblique path between the eyes and the brain. Fat saturation and oblique angles will be required, FLAIR may be helpful to suppress CSF, and 3D Fast Spin Echo will help suppress the signal from blood vessels if available. Ideally, Dixon fat saturation and 3D T1 /T2 FLAIR is a great combo if it's available, otherwise 2D fast spin echo is the best choice. +The optic nerves are paired nerves extending from the optic chiasm, just rostral to the pituitary gland, toward the eyes in an oblique dorsal plane. The optic nerves are not as commonly affected as the other cranial nerves, but do require more special imaging when it is necessary to assess them. To best assess the optic nerves, consider a few things: The nerves are small, surrounded by CSF, cushioned in fat, well vascularized, and take a tortuous and oblique path between the eyes and the brain. Fat saturation and oblique angles will be required, FLAIR may be helpful to suppress CSF, and 3D Fast Spin Echo will help suppress the signal from blood vessels if available. 
 + 
 +**Useful Sequences:** 
 + 
 +  * Dixon T1 or T2 FSE 
 +  * T2 FLAIR with Fat Saturation 
 +  * 3D FSE with Fat Saturation
  
 ===Special View for Optic Nerves=== ===Special View for Optic Nerves===
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 {{::dorsaloblsliceplan.png?600|}} {{::dorsaloblsliceplan.png?600|}}
  
-See GIFs below to get a sense of the anatomy. Sequence: 3D Isotropic PD FRFSE+See GIFs below to get a sense of the anatomy. 
  
 Dorsal Oblique T2 FLAIR Fat Sat Dorsal Oblique T2 FLAIR Fat Sat
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 Dorsal Oblique 3D PD FRFSE Dorsal Oblique 3D PD FRFSE
  
 +{{::dor3dpdopticnerves.gif?|}}
  
 ==**Sagittal Oblique**:== ==**Sagittal Oblique**:==
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 ====The Trigeminal Nerves==== ====The Trigeminal Nerves====
  
-====The Vestibulocochlear Nerves====+The Trigeminal nerves are 3 paired nerves extending from the brainstem rostrally. The three branches include the ophthalmic, maxillary, and mandibular, and serve sensory and motor functions for the face. Due to their relatively small size and oblique course, they can be tough to visualize much beyond their origins without high resolution imaging. When trigeminal nerve pathology is present, downstream effects of denervation may be seen such as muscle wasting or inability to close the mouth. These changes can readily be seen as an asymmetry in the muscle size on either side of the head, and sometimes hyperintensity on T2 weighted imaging. While there are no special views needed to visualize the nerves, high in-plane resolution  and thin slices are helpful, and slice coverage from the eyes through the brain is required. 
 + 
 +**Useful Sequences:** 
 + 
 +  * T1 or T2 FSE 
 +  * DWI b600-1000 
 +  * T1 Post Gd with Fat Saturation 
 + 
 +All three branches visualized on a DWI b1000 
 + 
 +{{::trigemnerve_normal_dwi.gif?|}} 
 + 
 +Right sided trigeminal tumor seen on DWI b1000 
 + 
 +{{::trigemtumorrsidelg.gif?}} 
 + 
 +In the slide below, notice the asymmetrical muscle size (blue arrow) and how fat saturation improves image quality after contrast administration. 
 + 
 +{{::trigemtumorlabeled.png?600|}} 
 + 
 + 
 +====The Vestibulocochlear / Facial Nerves==== 
 + 
 +The vestibulocochlear and facial nerves are located closely together in the inner ear and their origins can be well visualized on MRI with appropriate slice planning. Some common findings in animals with pathology in this area can include head tilt, and may be due to infection, inflammation, or neoplasia. A common source of pathology is infection within the bulla, air filled spaces just ventral to the inner ear. In certain cases, further high resolution imaging can be helpful. 
 + 
 +**Useful Sequences:** 
 + 
 +  * T1 FSE with Fat Saturation 
 +  * 3D T2 or PD FSE 
 +  * 3D FIESTA-C (GE)/CISS (Siemens) 
 + 
 +{{::vestibulocochlearnervesslide.png?600|}} 
 + 
 +{{::cochlea3dpd.gif?|}} 
 +