CRANIAL NERVES Flashcards
Which cranial nerves are purely sensory?
Olfactory
Optic
Vestibular
Which cranial nerves are purely motor?
Occulomotor
Trochlear
Abducens
Accessory
Hypoglossal
Which cranial nerves have sensory + motor functions?
Trigeminal
Facial
Glossopharyngeal
Vagus
Which occipital lobe does the right visual field come from?
The left occipital lobe
Visual field defect when there is a lesion in the optic nerve e.g. demyelination or occlusion of retinal artery?
Total blindness of ipsilateral eye
Visual field defect when there is a lesion in the optic chiasm e.g pituitary tumour?
Bitemporal hemianopia
Visual field defect when there is a lesion in both optic radiations e.g. parietal and temporal lobe stroke?
Contralateral homonymous hemianopia
Visual field defect when there is a lesion in the inferior radiation e.g. temporal lobe stroke?
Contralateral upper quadrantic anopsia
Visual field defect when there is a lesion in the superior radiation e.g. parietal lobe stroke?
Contralateral lower quadrantic anopsia
Visual field defect when there is a lesion in the occipital lobe e.g. occipital lobe stroke?
Contralateral homonymous hemianopia with macular sparing
Abducens nerve supplies what and does what?
Lateral rectus muscle
Abducts the eye
Trochlear nerve supplies what and does what?
Superior oblique muscle
(Hooks around the Trochlear which is a pulley on the medial aspect of the orbit)
Moves eye in down and out position
Occulomotor nerve supplies what and does what?
Motor innervation to levator palpebrae superioris, superior rectus, inferior rectus, medial rectus and inferior oblique muscle = all movements other than “down and out”
Parasympathetic supply to sphincter pupillae and ciliary muscles of the eye = constriction of pupil
Occulomotor nerve palsy signs…
Eye is down and out (loses superior, inferior and medial rectus muscles)
Pupil dilated (loss of parasympathetic tone of ciliary body)
Ptosis (loss of levator palpebrae muscle)
Abducens nerve palsy signs…
Unable to abduct the affected eye = horizontal diplopia
Trochlear nerve palsy signs…
Eye will be facing up and inwards
Defective downward gaze = vertical diplopia
Function of trigeminal nerve?
Sensation to face and sensory part of corneal reflex
Motor supply to muscles of mastication and Jaw jerk reflex
Function of the facial nerve?
Motor function to muscles of facial expression
Supplies anterior 2/3rds of the tongue for taste
Parasympathetic - glands of head and neck e.g. lacrimal, mucous glands and some salivary glands
What is the facial motor nucleus?
Why is this clinically relevant?
A round aggregation of motor neuron cell bodies found in the pontomedullary junction which are paired on the left and right side of the brain stem and are neatly divided in half
The superior half of the nucleus represents superior half of face, and inferior half represents inferior half of face
Superior half of the face derives conscious control from left and right primary motor cortex
Inferior half derives conscious control from only the contralateral primary motor cortex
A supranuclear lesion to 1 side (UMN lesion) will cause paralysis of only the contralateral lower half of the face because the upper half of the face is supplied bilaterally - e.g. stroke
An infranuclear lesion (LMN lesion e.g. middle ear tumour, infection- Bell’s palsy if idiopathic) will cause paralysis/weakness in both the upper and lower halves of one side of the face
What does Weber’s test tell you?
If pt hears louder in R ear then either conductive hearing loss in R ear OR conductive hearing loss in L ear
What does Rinne’s test tell you?
Normal response - louder in front of ear than on mastoid as air conduction is greater than bone conduction
If louder on mastoid then bone conduction > air conduction = conductive hearing loss in that ear