Radiological anatomy of the cranial nerves and technique of imaging

Radiological anatomy of the cranial nerves and technique of imaging.

INTRODUCTION. 1- Cranial nerves are the nerves that emerge directly from the brain (including the brainstem), in contrast to the spinal nerves (which emerge from segments of the spinal cord) [1] . 2 -The numbering of the cranial nerves is based on the order in which they emerge from the brain, front to back (brainstem) [1] . 3 -Unlike most cranial nerves, the olfactory and optic nerves consist of white-matter tracts and is not surrounded by Schwann cells [2] ..

Fig.1-View of the human brain from below showing the cranial nerves on an autopsy specimen.

What happens if they are affected?. NERVE SYMPTOMS OLFACTORY Inability to smell ( anosmia ), a distortion in the sense of smell ( parosmia ) [1] . OPTIC Affects specific aspects of vision [3] . OCCIUOLMOTOR Causes diplopia , and inability to coordinate the movements of both eyes ( strabismus ), eyelid drooping ( ptosis ) and pupil dilation ( mydriasis ) [4] . . TROCHLEAR Causes diplopia with affected with impaired superior oblique muscle [4] . TRIGEMINAL Trigeminal neuralgia , cluster headache , and trigeminal zoster [1] ..

ABDUCENT Causes diplopia with affected with impaired lateral rectus M [4] . FACIAL Inability to move the ipsilateral muscles of facial expression , including elevation of the eyebrow and furrowing of the forehead. Drooping mouth on the affected side and often have trouble chewing because the buccinator muscle is affected [1] . VESTIBULOCOCHLEAR Sensation of spinning and dizziness [1] . SNHL and damage to the VIIIth nerve can also present as repetitive and involuntary eye movements ( nystagmus ) [3] . Glossopharyngeal Provides sensory innervation to the oropharynx and back of the tongue [1] . Unilateral absence of a gag reflex [5] ..

VAGUS Major effects of damage to the vagus nerve may include a rise in blood pressure and heart rate. Isolated dysfunction of only the vagus nerve is rare, but can be diagnosed by a hoarse voice, due to dysfunction of one of its branches, the recurrent laryngeal nerve . [1] Acessory Impaired shoulder elevation and head-turning [1] . HYPOGLOSSAL Fasciculations or atrophy of the muscles of the tongue. weakness of tongue movement on one side. When damage persists the tongue will move towards the weaker [ 3 ] ..

ANATOMY AND COURSE OF THE INTRA CRANIAL NERVES (6).

NERVE ORIGIN CISTERN STATIONS LANDMARK EXIT III Anterior mid brain ventral to the cerebral aqueduct interpeduncular Cavernous sinus superior cerebellar and posterior cerebral arteries Superior orbital fissure IV Posterior midbrain Posteriorly into the ambient cistern and then curves anterior to the interpeduncular cisten Cavernous sinus superior cerebellar and posterior cerebral arteries Superior orbital fissure.

Trav-.

V large sensory root that runs medial to a smaller motor root arises from the pons Prepontine cistern In Meckel cave, the trigeminal nerve forms the trigeminal ( gasserian ) ganglion before splitting into three subdivisions. The ophthalmic V 1, maxillary V 2 and mandibular division v3. V1: SOF V2: foramen rotandum . V3: foramen ovale . VI Pons but traverse inferior to exit at the level pontomedullary junction Prepontine cistern Runs vertically along the posterior aspect of the clivus , within a fibrous sheath called the Dorello canal . The nerve then continues over the medial petrous apex and through the medial cavernous sinus SOF VII VIII Pons cerebellopontine angle cistern The nerves cross the porus acusticus and traverse the length of the internal auditory canal. within the internal auditory canal, the VIII nerve splits into three parts(cochlear, superior vestibular, and inferior vestibular). VII: Facial canal . VIII:.

IX Medulla Cerebellomedullary From the lateral cerebellomedullary cistern, the nerve plunges into the jugular. Jugular foramen X Medulla Cerebellomedullary From the lateral cerebellomedullary cistern, the nerve plunges into the jugular. Exits between the IX and XI cranial nerves Jugular foramen XI Medulla Upper cervical segments Cerebellomedullary cistern below the vagus . After leaving the spinal cord, the spinal rootlets pass superiorly through the foramen magnum into the cisterna magna join the cranial rootlets in the lateral cerebello -medullary cistern. Jugular foramen.

X II. The hypoglossal nerve arises the a into the lateral cerebello -medullary cistern, The hypoglossal nerve then exits the skull via the hypoglossal canal. I . The neurosensory cells for smell reside in the olfactory epithelium >>cribriform plate of the ethmoid bone into the olfactory bulb >>courses posteriorly through the anterior cranial fossa >>>terminate in the inferomedial temporal lobe, uncus, and entorhinal cortex. II. It includes four anatomic segments: retinal, orbital, canalicular, and cisternal . The retinal segment leaves the ocular globe through optic foramen of the sclera>>The orbital segment>>>The optic canal, below the ophthalmic artery >>>Finally, the cisternal suprasellar cistern>>> optic chiasm. The anterior cerebral artery passes over the superolateral aspect of the cisternal segment of the nerve..

Illustration.

Cranial Nerves MRI Planning Protocol. Steady-State Free Precession (SSFP) GE : FIESTA (Fast Imaging Employing Steady- stateAcquisition ) Siemens : FISP (Fast Imaging with Steady-state Precession) Philips: FFE (Fast Field Echo), b-FFE (Balanced Fast Field Echo).

How to protocol ?. Routine MRI Brain sequences followed by FIESTA. 1-Routine Brain includes: ** Axial T1, FLAIR, T2w, Dwi,T2*GRE, Coronal T2, Sagittal T2. 2- Axial 3 D FIESTA. 3-In selected cases Contrast enhanced T1..

What is the plane?. Slap oriented at right angle to the vertical axis of the brain stem covering its whole surface area..

REFERENCES.

1- Vilensky , Joel; Robertson, Wendy; Suarez- Quian , Carlos (2015). The Clinical Anatomy of the Cranial Nerves: The Nerves of "On Olympus Towering Top". Ames, Iowa: Wiley-Blackwell. ISBN 978-1-118-49201-7 . 2- Wilson- PauwelsL , Akesson EJ, Stewart PA. Cranial nerves: anatomy and clinical comments. Philadelphia, Pa: Decker, 1988. 3-Kandel, Eric R. (2013). Principles of neural science (5. ed.). Appleton and Lange: McGraw Hill. pp. 1533–1549. ISBN 978-0-07-139011-8 . 4- Norton, Neil (2007). Netter's head and neck anatomy for dentistry. Philadelphia, Pa.: Saunders Elsevier. ISBN 978-1-929007-88-2 . : 5- Bickley, Lynn S., Peter G. Szilagyi , and Barbara Bates. Bates' Guide to Physical Examination and History-taking. Philadelphia: Wolters Kluwer Health/Lippincott Williams & Wilkins, 2013. 6- Sujay Sheth , Barton F. Branstetter , and Edward J. Escott. Appearance of Normal Cranial Nerves on Steady-State Free Precession MR Images: RadioGraphics 2009; 29:1045–1055..

THANK YOU.