Cranial Nerve Lesions Flashcards
Olfactory Nerve Lesion
Anatomy
-Series of bipolar neurones which past through the cribriform plate
Signs
-Reduced taste and smell but not to ammonia (ammonia detected by trigeminal nerve)
Causes
-Trauma, frontal lobe tumour, meningitis
Optic Nerve Lesion
Anatomy
- Axons of retinal ganglion cells
- Nasal fibres decussate
Signs and causes
- Visual field deficits
- Scotomas
- Monocular blindness (e.g. MS GCA)
- Bilateral blindness (methyl alcohol, tobacco amblyopia, neurosyphilis)
- Bitemporal hemianopia (adenoma, internal carotid aneurysm)
- Homonymous hemianopia
- Pupillary abnormalities
- Optic neuritis (demyelination)
- Optic atrophy
- Papilloedema
Oculomotor Nerve Lesion
Anatomy
-Nerve emerges from brainstem and pierces dura and passes with Iv and VI to enter orbit
Signs
-Fixed and dilated pupil which does not accommodate, then ptosis develops, then internal ophthalmoplegia
Causes
- DM, GCA, syphilis, posterior communicating artery aneurysm
- If no dilation; medical causes
Trochlear Nerve Lesion
Anatomy
-Passes backwards in the brainstem
Signs
- Diplopia
- Tilting away from affected side
Causes
-Rare most commonly due to trauma
Trigeminal Nerve Lesion
Anatomy
- Three trunks
- Ophthalmic, maxillary, mandibular
- Mandibular contains sensory and motor
Signs
- Reduced sensation over affected area
- Weakness of jaw clenching
Causes
- Sensory: neuralgia, herpes, carcinoma
- Motor: bulbar palsy, acoustic neuroma
Abducens Nerve Lesion
Anatomy
Signs
-Inability to look laterally
Causes
- MS, pontine CVA
- Long extracerebral course so considered a false localising sign
Facial Nerve Lesion
Anatomy
-Mainly motor
Signs
-Facial weakness
Causes
- UMN: Bell’s palsy, polio, skull fracture
- LMN: stroke, tumour
Vestibulocochlear Nerve Lesion
Anatomy
-Carries two groups of fibres; hearing and balance and posture
Signs
- Unilateral sensorineural deafness, tinnitus
- Slow growing lesions seldom present with vestibular symptoms as compensation has time t to occur
Causes
- Paget’s (most common for 8 to be affected but any can be)
- Ménière’s, herpes
Glossopharyngeal Nerve Lesion
Anatomy
-Sensory, motor and parasympathetic fibres
Signs
- Unilateral lesions do not cause deficit because of bilateral corticobulbar connections
- Bilateral lesions result in pseuduobulbar palsy
Causes
-Trauma, brainstem lesions, cerebellopontine angle and tumours
Vagus Nerve Lesion
Anatomy
-The wanderer
Signs
- Palatal weakness can cause nasal speech and nasal regurgitation
- Palate moves asymmetrically when patient says ahh
Causes
-Trauma, brainstem lesions, tumours in the cerebellopotine angle
Accessory Nerve Lesion
Anatomy
-Motor
Signs
-Weakness and wasting
Causes
-Same as vagus
Hypoglossal Nerve Lesion
Anatomy
-Passes
Signs
- Wasting of ipsilateral
- Tongue towards
Causes
-Polio, syringomyelia, median branch thrombosis
