Cranial nerves Flashcards
What are the identification of cranial nerves?
- Diameter
- Course
- Vessels
- CSF
What is cranial nerve III?
Oculomotor nerve
What is cranial nerve IV?
Trochlear nerve
What is cranial nerve V?
Trigeminal nerve
What is cranial nerve VI?
Abducens nerve
What are the segments of CN?
- Central (nuclei, central fascicles)
- cisternal (brainstem > dura)
- Cavernous sinus (SOF) - intraforaminal/intracanalicular
What can cisternal segments be visualised with? 1.5T
- 2D-SE/FSE/TSE
- 3D-CISS (Siemens)
- 3D-FSE/TSE
- 3D-FASE (Toshiba)
- FIESTA (GE)
What is CISS?
assessment of the anatomical variations and various pathologies involving the cranial nerves and central nervous system
What can cisternal segments be visualised with? 3.0T
3D-CISS (Siemens) SPACE (Siemens) FIESTA-C (GE) CUBE (GE) Balanced fast-field echo [b-FFE] (Philips) VISTA (Philips)
What are the features of CISS?
- Steady-state-gradient-echo sequence
- Flow compensated
- MR cisternography
What are the 3D set of data for CISS?
- Reconstructions in any desired plane
- Slice orientation - course of cranial nerves
- 0.7 (0.5) mm slice thickness
What are examples of big cranial nerves?
- Optic nerve
- Trigeminal nerve
- Oculomotor nerve
What are the percentages that can be observed for the big cranial nerves on T2w TSE and 3D-CISS?
Optic nerve;
T2-w TSE: 100%
3D-CISS: 100%
Trigeminal nerve:
T2-w TSE: 100%
3D-CISS: 100%
Oculomotor nerve:
T2-w TSE: 82.5%
3D-CISS: 100%
What are examples of the small cranial nerves?
Abducent nerve
Hypoglossal nerve
Trochlear nerve
What are the percentages that can be observed for the small cranial nerves on T2w TSE and 3D-CISS
Abducent nerve:
T2-w TSE: 32.5%
3D-CISS: 100%
Hypoglossal nerve:
T2-w TSE: 10%
3D-CISS: 100%
Trochlear nerve:
T2-w TSE: 7.5%
3D-CISS: 47.5%
Big CN: CN II, CN III, CN V (sensory)
3D-CISS = conventional 2D TSE
Small CN: CN IV, CN VI, CN XII
3D-CISS»_space; conventional 2D TSE
Trochlear nerve
3D-CISS: limitations
Technique has to be optimised
What sequences are intracanalicular and intraforaminal segment sensitive to with contrast?
T1w 3D-TOF (MRA) + CM 3D-MPRAGE (Siemens) + CM 3D-GRASS (GE) + CM 3D-SPGR (GE) + CM
What is the nucleus of oculomotor nerve?
Tegmentum of mesencephalon
superior colliculi
Diametr 2.5-3mm
Where is the trochlear nerve located?
Caudal mesencephalon beneath the cerebral aqueduct
What are the nucleus of trochlear nerve?
- Tegmentum of mesencephalon
2. Inferior colliculi
Where does the decussation of central fascicles occur for the trochlear nerve?
Superior medullary velum
What are the problems of cisternal segments?
Smallest CN 0.2-1 mm Longest intracranial course 60 mm Longest cisternal segment 15-20 mm Differentiation from SCA branches small veins joining petrosal vein “Hidden” between two folds of tentorium Subtentorial segment
What are the initial cisternal segments?
A) Short segment close to the brainstem > Quadrigeminal cistern
B) Long segment far from brainstem
- Subtentorial segment
> Ambient cistern
What is CN IV (trochlear nerve) identification?
3D-CISS + 3D-TOF ± CM
What are the landmarks for trochlear nerve?
- Inferior colliculi
2. Superior medullary velum
What is velum?
Very thin sheet covering the aqueduct
What are the segments for abducent nerve (CN VI)?
- Nucleus: Floor of 4th ventricle
- Pontomedullary sulcus
- Prepontine cisterne
- Dorello’s canal
- Cavernous sinus (SOF)
- Orbita (lateral straight muscle)
Diameter: 2.2 mm
What are the landmark for Abducent nerve?
- Facial colliculus
- Dorello’s canal
- Length of CSF invagination
< 1-3mm
What is found within cavernous sinus?
3rd, 4th , part of 5th nerve and 6th nerve
What are frontal eye field?
Region located in the frontal cortex
Responsible for saccadic eye movement for the purpose of visual field perception and awareness
What is Trigeminal ganglion?
Sensory ganglion of trigeminal nerve that occupies a cavity in the dura mater, covering the trigeminal impression near apex of petrous part of temporal bone
What is the identification for trigeminal ganglion?
3D-CISS + CM
How is facial nerve located?
Anteriorly
How is cochlear nerve located?
Superior and Inferior
What is the function of the vestibulocochlear nerve (CN VIII)?
- Information comes from cochlea
- Vestibular nuclei
- Relay station
- Up to the cortex
What are the components of Hypoglossal nerve?
- Premedullary cistern (3-6 rootlets)
- Hypoglossal canal (1-2 truncs)
- Extracranial segments (1 trunc)
What are the lower cranial nerve complex?
CN IX-XI
- Glossopharyngeal N (CN IX)
- Vagus N (CN X)
- Accessory N (CN XI)
What is located in CN VII?
chorda tympani & greater petrosal nerves
What is located in CN IX?
lingual branch
What is located in CN X?
superior laryngeal branch
How is CNVII located?
Rostral
Hhow is CN X located?
Caudal
What is the identification for hypoglossal canal?
3D-CISS + CM
3D-MPRAGE
+ CM
How can all cisternal segments of all CN be visualised?
in vivo at 1.5 T
Cranial nerve techniques
Location of nuclei
Course of cisternal segments
Exit through dura
Neurovascular contacts
Optimised MRI technique
Cisternal S; Meckel‘s cave > 3D-CISS
Intraforaminal/ intracanalicular S; Cavernous Sinus »_space; 3D-CISS / 3D-TOF / 3D-MPRAGE + CM
Trigeminal ganglion > 3D-CISS / 3D-TOF + CM
Neurovascular contacts ; CN IV > 3D-CISS + 3D-TOF ± CM
