Cranial Nerve Disorders Flashcards
What Cranial nerve(s) would be affected by a midbrain lesion?
Oculomotor Bilaterally
What Cranial nerve(s) would be affected by a lesion in the Sup Orbital fissure?
Oculomotor
Trochlear
Abducens
Opthalmic (V1)
What Cranial nerve(s) would be affected by a lesion in the Pontomedullary junction?
VI/VII/VIII
What Cranial nerve(s) would be affected by a lesion at the cerebellopontine angle?
Trigeminal & Vestibulocochlear
Describe some lesions that could damage a cranial nerve?
ISchaemia or tumour within the brain
Meningitis or SAH whilst crossing the subarachnoid space
Skull tumours outside the cranium
Name a condition that can cause optic neuritis?
MS
What are the symptoms of optic neuritis?
- Monocular visual loss
- Pain on eye movement
- Reduced visual acuity & Colour vision
- Papilloedema
What could cause a dilated pupil?
Naturally:
- Youth
- Dim lighting
- Anxiety or Excitement
Unnaturally:
- Mydriatic eye drops
- Amphetamines/cocaine
- third nerve palsy
- Brain death
What could cause a constricted pupil?
Naturally:
- Old Age
- Bright Light
Unnaturally:
- Miotic Eye Drops
- Opiates
- Horners Syndrome (comes with anhydrosis and ptosis)
Define horner’s Syndrome
Something cutting off or compressing the sympathetic innervation to the eye and face (unilateral)
Can be intracranial lesions at the point where the sympathetic fibres leave thalamus and enter brainstem or in spinal cord or after they leave the spinal cord (e.g. pancoast tumour)
It causes:
- Miosis (Constricted pupil)
- Anhydrosis
- Ptosis
What type of cranial nerve palsies can cause eye movement disorders?
- Isolated nerve palsy to III, IV or VI
- Any combination of the above
- Supranuclear gaze palsy
- Nystagmus (VIII)
What is a supranuclear gaze palsy?
An inability to look in a particular direction due to impairment in the cerebrum (Above the cranial nerve nuclei)
What could cause an Isolated III nerve palsy?
Microvascular conditions like diabetes or hypertension could cause a painless, pupil sparing III palsy
Compressive conditions like raised ICP or a Post. Comm. Art. Aneurysm could cause a a painful III palsy with a dilated pupil
What could cause an isolated VI nerve Palsy?
- Idiopathic
- Diabetes
- Meningitis
- Raised ICP
What are the common causes of pathological nystagmus?
- Congenital (may never notice visual problems)
- Visual impairment
- Vestibular problems
- Brainstem disease (Affecting VIII)
- Cerebellar Disease
- Alcohol
- Toxic Med
Name 2 meds that can cause pathological nystagmus?
- Phenytoin
- Carbamazepine
Both are epileptic medications
What causes Trigeminal Neuralgia?
A vascular loop compressing the V nerve in the posterior fossa
What is trigeminal neuralgia?
Paroxysmal attacks of Lancinating pain (Stabbing/piercing) in the face
Brought on my temp changes, wind, touch or chewing
How do we treat trigeminal neuralgia?
Carbamezepine
Surgery
Define Bell’s Palsy?
A LMN idiopathic facial nerve palsy:
- Unilateral facial weakness
- Often preceded by ear pain
- Risk of corneal damage form open eye
How do you treat bell’s palsy
Steroids!
Whats different about an UMN and LMN Facial nerve palsy?
Facial nerve fibres to lower face (below zygomatic arch) have UMNs from the contralateral cortex
So in an UMN or LMN lesion the lower face is always affected
However the facial nerve fibres to the upper face recieve UMNs form both hemispheres
Meaning if theres an UMN lesion the forehead is preserved but a LMN will affect that entire side of the face
Examples of UMN vs LMN facial palsies?
UMN - Stroke or tumour
LMN - Bells Palsy, Lymes disese or sarcoid
What is Vestibular Neuronitis?
Sudden onset VIII palsy causing:
- Vomiting
- Disabling Vertigo
They tend to recover fully over a few weeks
What are bulbar and pseudobulbar palsy?
Palsys afffecting the 9th-12th cranial nerves causing Inability to control movements (such as chewing and speaking)
Due to bilateral lesions of the:
- corticobulbar tracts i.e.
UMNs (Pseudobulbar)
- Motor Cranial Nerves i.e. LMNs (Bulbar)
What could cause pseudobulbar palsy?
Bilateral UMN lesion
- Vascular lesions of both internal capsules
- Motor Neuron Disease
Difference between pseudobulbar and bulbar palsy presentations?
Bulbar (LMN):
- wasted, fasciculating tongue
- dysarthria (slurred Speech)
- dysphonia (Abnormal sound production)
- dysphagia
Pseudobulbar (UMN):
- Hyperreflexia (Gag, Jaw Jerk)
- Dysarthia, Dysphonia, Dysphagia
- Spastic Immobile Tongue
What should you be careful of in patients with bulbar or pseudobulbar palsies?
Feeding them, they will likely choke
What could cause Bulbar Palsy?
Bilateral LMN lesions affecting IX-XII
- MND
- Polio
- Tumour
- Vascular lesion of medulla
- Syphilis
