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Cranial Nerves Overview

Main Text

TERMINOLOGY

Abbreviations

• Olfactory nerve (CNI)
• Optic nerve (CNII)
• Oculomotor nerve (CNIII)
• Trochlear nerve (CNIV)
• Trigeminal nerve (CNV)
• Abducens nerve (CNVI)
• Facial nerve (CNVII)
• Vestibulocochlear nerve (CNVIII)
• Glossopharyngeal nerve (CNIX)
• Vagus nerve (CNX)
• Accessory nerve (CNXI)
• Hypoglossal nerve (CNXII)

IMAGING ANATOMY

Overview

• Cranial nerve groupings based on area of brainstem origin

Diencephalon: CNII

Mesencephalon (midbrain): CNIII and CNIV

Pons: CNV, CNVI, CNVII, and CNVIII

Medulla: CNIX, CNX, CNXI, and CNXII

ANATOMY IMAGING ISSUES

Imaging Recommendations

• Best imaging modality for any simple or complex cranial neuropathy is MR

Single exception to this directive is distal vagal neuropathy where it is necessary to image to aortopulmonic window on left

– CECT better here as less affected by breathing, swallowing, and coughing movements
• If lesion located in bony area, such as skull base, sinuses, or mandible, bone CT highly recommended to provide complementary bone anatomy and lesion-related information

Contrast enhancement of CT is not necessary if full T1, T2, and T1 C+ MR available

Imaging Approaches

• Remember: Cranial nerves do not stop at skull base
• Radiologist must image entire extent of affected cranial nerve

CNI, CNII, CNIII, CNIV, and CNVI : Include focused orbital sequences

CNV : Include entire face to inferior mandible if V3 affected

CNVII : Include CPA, temporal bone, and parotid space

CNVIII : Include CPA-IAC and inner ear

CNIX-XII : Include basal cistern, skull base, nasopharyngeal carotid space

– CNX : To fully evaluate for recurrent laryngeal nerve lesion, follow carotid space to aortopulmonic window on left, cervicothoracic junction on right

– CNXII : Remember to reach hyoid bone to include distal loop as it rises into sublingual space

Imaging Pitfalls

• Do not forget to image extracranial structures associated with cranial nerve affected

CLINICAL IMPLICATIONS

Clinical Importance

• Cranial nerves and their functions

Olfactory nerve ( CNI )

– Sense of smell

Optic nerve ( CNII )

– Sense of vision

Oculomotor nerve ( CNIII )

– Motor to all extraocular muscles except lateral rectus (CNVI) and superior oblique (CNIV)

– Parasympathetic supply to ciliary and pupillary constrictor muscles

Trochlear nerve ( CNIV )

– Motor to superior oblique muscle

Trigeminal nerve ( CNV )

– Motor (V3) to muscles of mastication, anterior belly digastric, mylohyoid, tensor tympani and palatini

– Sensory to surface of forehead and nose (V1), cheek (V2), and jaw (V3)

– Sensory to surfaces of nose, sinuses, meninges, and external surface of tympanic membrane (auriculotemporal nerve)

Abducens nerve ( CNVI )

– Motor to lateral rectus muscle

Facial nerve ( CNVII )

– Motor to muscles of facial expression

– Motor to stapedius muscle

– Parasympathetic to lacrimal, submandibular, and sublingual glands

– Anterior 2/3 tongue taste ( chorda tympanic nerve )

– General sensation for periauricular skin, external surface of tympanic membrane

Vestibulocochlear nerve ( CNVIII )

– Senses of hearing and balance

Glossopharyngeal nerve ( CNIX )

– Motor to stylopharyngeus muscle

– Parasympathetic to parotid gland

– Visceral sensory to carotid body

– Posterior 1/3 tongue taste

– General sensation to posterior 1/3 of tongue and internal surface of tympanic membrane

Vagus nerve ( CNX )

– Motor to pharynx-larynx

– Parasympathetic to pharynx, larynx, thoracic and abdominal viscera

– Visceral sensory from pharynx, larynx, and viscera

– General sensation from small area around external ear

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You may also need
Hypoglossal Nerve (CNXII)
Insula and Parainsula Areas (Areas 13, 43)
Primary Somatosensory Cortex (Areas 1, 2, 3)
Parahippocampal Gyrus (Areas 28, 34, 35, 36)
Primary Visual and Visual Association Cortex (Areas 17, 18, 19)
Inferior Parietal Lobule (Areas 39, 40)
Subgenual Cingulate Cortex (Area 25)
Temporal Cortex (Areas 20, 21, 22)

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Tags: Imaging Anatomy Brain and Spine

Mar 13, 2021 | Posted by admin in NUCLEAR MEDICINE | Comments Off

Main Text

TERMINOLOGY

Abbreviations

IMAGING ANATOMY

Overview

ANATOMY IMAGING ISSUES

Imaging Recommendations

CLINICAL IMPLICATIONS

Clinical Importance

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