Cranial Nerve Lesions

Question 1

Cranial Nerve I

Answer 1

Anosmia caused by Head Injury (Shearing of Olfactory Neurones) or Tumours of Olfactory Groove; Might also be lost in Parkinson’s Disease; Detailed testing is difficult; Requires
commercially available kits e.g. Scratch and sniff, Odour filled pens

Question 2

Visual Acuity

Answer 2

Visual Acuity by Snellen Chart; 6 (or 3) Metres from Chart, corrected for refractory errors with
Lenses or Pinhole; Recorded as distance in metres from the chart over distance at which line is legible e.g. 6/6 is normal, 6/60 is poor

Question 3

Visual Field Defects

Answer 3

Mononuclear (Optic Nerve), Bitemporal Hemianopia (Chiasm), Homonymous Hemianopia (Optic Tract), Homonymous Quadrantanopia (Baum’s/Meyer’s
Loops), Homonymous Hemianopia with Macular Sparing (Occipital Cortex), Hemiscotoma
(Occipital Pole)

Question 4

Total Optic Nerve Lesion

Answer 4

Unilateral Blindness

with Loss of Pupillary Light Reflex

Question 5

Unilateral vision loss

Answer 5

Unilateral Visual Loss commencing with Central/Paracentral Scotoma; Most fibres of Optic
Nerve subserve Macular vision; Disproportionately
affects Central Vision and Colour

Question 6

Optic Neuropathy

Answer 6

Reduced Acuity in affected eye,
Central Scotoma, Impaired Colour Vision, Afferent
Pupillary Defect, Optic Atrophy (Late stage; appears
as pale disc)
o Inflammatory, Demyelination,
Compression/Trauma, Toxic, Ischaemic,
Hereditary (e.g. Leber’s), Nutritional
Deficiency, Infection, Neurodegeneration,
Papilloedema

Question 7

Papilloedema

Answer 7

• Swelling of the Optic Disc; Disc pinkness, Blurring and Heaping of Disc Margins; Loss of spontaneous pulsation of Retinal Veins within the Disc
• Physiological cup becomes obliterated; Disc engorged with Dilated Vessels; Small
Haemorrhages around the Disc
• Hyaline Bodies (Drusen) can be mistaken for Disc Swelling; IV Fluorescein Angiography for
diagnosis; Retinal leakage seen with Papilloedema
• Few Visual symptoms; Momentary Visual Obscuration with changes in posture; Blind spot
enlarged but not noticed by patient

Question 8

Afferent Pupillary Defect

Answer 8

– Complete Optic Nerve
Lesion causing Dilated Pupil; Unreactive to light (loss
of Direct Reflex) and Consensual Reflex is lost;
Affected pupil contracts in response to light into
intact, contralateral eye (Consensual Reflex in
another eye preserved)

Question 9

Relative Afferent Pupillary Defect

Answer 9

Incomplete damage to one optic nerve relative to other; When light is swung, affected pupil dilates slightly when
illuminated and constricts when another eye is
illuminated (Consensual Reflex is stronger than
Direct Reflex)

Question 10

Horner’s Syndrome

Answer 10

Unilateral Miosis, Partial
Ptosis, Anhidrosis; Subtle Conjunctival Injection and
Enophthalmos

Question 11

Myotonic Pupil

Answer 11

Dilated, Irregular Pupil; Common and often unilateral
o Slow or no response to bright light; Incomplete
Constriction to Convergence
o Due to denervation of Ciliary Ganglion; Sometimes
associated with Diminished or Absent Tendon Reflexes

Question 12

Argyll Robertson Pupil

Answer 12

Small, Irregular Pupil fixed to light but Constricts on Convergence; Lesions is around Cerebral Aqueduct
o Neurosyphilis, Diabetes or Multiple Sclerosis

Question 13

Unilateral Destructive Lesion

Answer 13

allows eyes to be driven
by Contralateral pathway e.g. Left Frontal Lesion leads
to Failure of Conjugate Lateral Gaze to the Right

Question 14

Acute FEF

Answer 14

eyes deviated to look towards side of lesion; There is usually a contralateral
Hemiparesis

Question 15

Internuclear Ophthalmoplegia (INO)

Answer 15

Damage to MLF causes INO; E.g. Right INO due to lesion of right MLF; On attempted Left Lateral Gaze, Right eye fails to adduct; Left eye develops Nystagmus in Abduction; Side of lesion is side of Impaired Adduction rather than Nystagmus; If Bilateral, Pathognomonic of MS

Question 16

One and a Half Syndrome

Answer 16

PPRF, Abducens Nuclear
and MLF Infarction leads to Ipsilateral Horizontal Gaze Palsy and INO; Abduction of
Contralateral eye (with Nystagmus) is the only Horizontal eye movement possible
o Vertical Gaze and Convergence are preserved

Question 17

Vertical Gaze

Answer 17

Failure of Upgaze due to Dorsal Midbrain Lesions (E.g. Pinealomas, Infarction)
o Parinaud’s Syndrome – Tectal Plate affected causing failure of Pupillary Light Reflex
o Also occurs in certain degenerative disorders e.g. Progressive Supranuclear Palsy

Question 18

Nystagmus

Answer 18

Rhythmic Oscillation of Eye Movement; Either Jerk or Pendular; Must be
sustained with Binocular Gaze; Few beats at extreme gaze is normal

Question 19

Jerk Nystagmus

Answer 19

Fast/Slow Oscillation; Seen in Vestibular, Vestibulocochlear Nerve, Brainstem and Cerebellar Lesions; Direction of Fast movement (Reflex attempt to correct slower Primary Movement)
o Horizontal/Rotary Jerk – Nystagmus might lead to Vertigo (Acute and Transient in Peripheral lesions, Long-Lasting in Central)
o Vertical Jerk Nystagmus typically due to Central lesions
o Down-Beat Jerk Nystagmus – Lesions around Foramen Magnum

Question 20

Pendular Nystagmus

Answer 20

Movement to-and-fro; Similar Velocity and Amplitude; Usually Vertical
and present in all directions of Gaze; Generally Ocular or Congenital

Question 21

Oculomotor Palsy

Answer 21

• Unilateral Ptosis (Levator Weakness), Eye Deviated down and out, Fixed and Dilated Pupil
• Sparing of the Pupil suggests Parasympathetic fibres are undamaged (Medical Oculomotor
Palsy) and can be caused by Diabetes
• Other causes include PComm Aneurysm, Atheroma, Coning, Midbrain Infarction (E.g.
Weber’s), Midbrain Tumours

Question 22

Trochlear Nerve Palsy

Answer 22

• Torsional Diplopia (Double vision at an angle) when attempting to look down; Head is tilted
away from affected side
• Commonly due to Head Injury; Bilateral Palsy can occur

Question 23

Abducens Nerve Palsy

Answer 23

• Horizontal Diplopia maximal on looking on side of lesion; Eye cannot be fully Abducted; Esotropia (Inward Eye Deviation)
• Nuclei can be damaged (e.g. MS, Infarction); In raised ICP, Compression against Petrous Temporal Bone; Nerve Sheath might be infiltrated by tumours e.g. Nasopharyngeal
Carcinoma; Microvascular Ischaemia may occur in Diabetes followed by Recovery within 3
months for most cases

Question 24

Trigeminal Nerve Palsy

Answer 24

• Complete Lesion causes Unilateral Facial Sensory loss, Anterior 2/3rds of Tongue and Buccal
Mucosa; Jaw Deviates towards ipsilateral side; Diminished Corneal Reflex is early sign
• Brainstem Pathology, Cerebellopontine Angle Tumours, Cavernous Sinus and Skull Base
Pathology; Peripheral Branches might be damaged (e.g. Numb Chin Syndrome in Breast Cancer due to Breast Ca Metastases

Question 25

UMN Facial Nerve Palsy

Answer 25

Weakness of lower part of Contralateral Face; Frontalis is spared (e.g. Eyebrows,
Blinking) due to Decussating fibres from Contralateral Facial Nerve; Relative preservation of
Spontaneous Emotional movement compared to Voluntary Movement

Question 26

LMN Facial Nerve Palsy

Answer 26

Complete Unilateral Weakness of all muscles of Facial Expression; Angle of Mouth falls,
Unilateral Dribbling; Frowning and Eye Closure are weak; Corneal exposure and Ulceration
can occur; Taste sensation is frequently impaired

Question 27

Causes of Facial Nerve Palsy

Answer 27

Most common UMN lesion is due to Hemispheric Stroke; Can also be due to Lesion in Pons (Might affect PPRF and CST as well), CPA Tumours, Bell’s Palsy, Trauma, Middle Ear Infection and Ramsay Hunt Syndrome (Herpes Zoster), Parotid Gland
Tumours or damage during surgery

Question 28

Bell’s Palsy

Answer 28

1 In 5000; Acute Facial Palsy due to Viral Infection (? Herpes Simplex); Unilateral
LMN Facial Weakness, Taste loss and Hyperacusis (Innervates Stapedius)
o Ear and Palate examined for Vesicles (Ramsey-Hunt = Shingles of Geniculate
Ganglion); Parotid Tumours, Middle Ear Infections to be excluded; Rule out
involvement of other CN; Lyme disease, HIV seroconversion

Question 29

Vestibulocochlear Nerve Palsy

Answer 29

• Deafness, Tinnitus – Testing of Sensorineural and Conductive Deafness using 256Hz fork; Pure
Tone Audiometry and Auditory thresholds
• Vestibular Function Testing by Head Impulse Test, Hallpike Test and Epley Particle Repositioning Manoeuvre

Question 30

Glossopharyngeal Nerve Lesions

Answer 30

Unilateral lesion causes diminished sensation on same side

Question 31

Vagus Nerve Palsy

Answer 31

Ipsilateral Failure of Voluntary and Reflex Elevation of the Soft Palate (leads to Uvula being drawn to Contralateral side) and Ipsilateral Vocal Cords

Question 32

Bilateral Lesions of both nerves (9+10)

Answer 32

Palatal Weakness, Reduced Palatal Sensation, Absent

Gag Reflex, Dysphonia, Choking with Nasal Regurgitation

Question 33

Bulbar Palsy

Answer 33

Palatal, Pharyngeal and Tongue weakness of LMN or Muscle Origin

Question 34

Recurrent Laryngeal Nerve

Answer 34

Paralysis causes Hoarseness (Dysphonia) and Failure of
Explosive cough (Leading to Bovine Cough)
o No visible Palatal Weakness; Vocal Cord Paralysis seen endoscopically
o Bilateral Acute Lesions can cause Respiratory Obstruction
o Left Recurrent Laryngeal Nerve more commonly damaged than the Right; Causes
include Mediastinal Tumours, Invasion from Bronchial Carcinoma, Aortic Aneurysm or
Trauma/Surgery of Neck and Thorax

Question 35

CN 11 Palsy

Answer 35

Weakness of SCM, Trapezius; Can be caused by Nerve section (i.e.
Iatrogenic) leading to Persistent Neuralgic Pain

Question 36

Hypoglossal Nerve Palsy

Answer 36

Unilateral Tongue Weakness, Wasting and Fasciculation; Protruded Tongue deviates towards weaker side (“Lick the Lesion”);
o Bilateral Supranuclear (UMN) Lesions lead to slow limited tongue movements and
stiff tongue; Fasciculation is absent

Question 37

Bulbar Palsy

Answer 37

• LMN weakness of muscles controlled by
CN IX, X, XI, XII
• Caused by disease of CN Nuclei, Lesions
of CN, NMJ disorders (e.g. MG) or Muscular disorders

Question 38

Pseudobulbar Palsy

Answer 38

• UMN Lesions of CN IX, X, XI, XII
• Stiff, slow, spastic tongue (Not wasted),
Dysarthria and Dysphagia; Gag and
Palatal Reflexes preserved; Jaw Jerk
exaggerated
• Emotional Lability often accompanies
• MND, Stroke, Neurodegeneration, TBI,
MS (Late event)