Cranial Nerve Lesions Flashcards
(38 cards)
Cranial Nerve I
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
Visual Acuity
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
Visual Field Defects
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)
Total Optic Nerve Lesion
Unilateral Blindness
with Loss of Pupillary Light Reflex
Unilateral vision loss
Unilateral Visual Loss commencing with Central/Paracentral Scotoma; Most fibres of Optic
Nerve subserve Macular vision; Disproportionately
affects Central Vision and Colour
Optic Neuropathy
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
Papilloedema
• 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
Afferent Pupillary Defect
– 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)
Relative Afferent Pupillary Defect
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)
Horner’s Syndrome
Unilateral Miosis, Partial
Ptosis, Anhidrosis; Subtle Conjunctival Injection and
Enophthalmos
Myotonic Pupil
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
Argyll Robertson Pupil
Small, Irregular Pupil fixed to light but Constricts on Convergence; Lesions is around Cerebral Aqueduct
o Neurosyphilis, Diabetes or Multiple Sclerosis
Unilateral Destructive Lesion
allows eyes to be driven
by Contralateral pathway e.g. Left Frontal Lesion leads
to Failure of Conjugate Lateral Gaze to the Right
Acute FEF
eyes deviated to look towards side of lesion; There is usually a contralateral
Hemiparesis
Internuclear Ophthalmoplegia (INO)
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
One and a Half Syndrome
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
Vertical Gaze
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
Nystagmus
Rhythmic Oscillation of Eye Movement; Either Jerk or Pendular; Must be
sustained with Binocular Gaze; Few beats at extreme gaze is normal
Jerk Nystagmus
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
Pendular Nystagmus
Movement to-and-fro; Similar Velocity and Amplitude; Usually Vertical
and present in all directions of Gaze; Generally Ocular or Congenital
Oculomotor Palsy
• 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
Trochlear Nerve Palsy
• 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
Abducens Nerve Palsy
• 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
Trigeminal Nerve Palsy
• 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
