cranial nerve lesions

Question 1

optic neuritis: Definition

Answer 1

Optic neuritis is a broad term expressing inflammation, degeneration, or demyelination of the optic nerve. It includes:

• papillitis or anterior optic neuritis - the intraocular portion of the nerve is affected, and the optic disc is swollen
• retrobulbar neuritis - optic neuritis in which the disc is not swollen
• neuroretinitis - optic disc and adjacent temporal retina are affected

Question 2

optic neuritis: Aetiology

Answer 2

Multiple sclerosis is the most common cause of retrobulbar neuritis accounting for 25-60% of cases.

Other causes of optic neuritis:

• other demyelinating disease, e.g. Devic’s disease
• toxic amblyopia
• metabolic - vitamin deficiencies, especially of B12; severe anaemia
• ischaemia - diabetes mellitis; temporal arteritis; arteriosclerosis
• familial - Leber’s disease

infection:

• viral - herpes zoster, infectious mononucleosis, typhoid fever
• bacterial - neurosyphilis, meningitis, tuberculosis
• other - toxoplasmosis

Question 3

optic neuritis: s/s

Answer 3

The clinical features of optic neuritis are divided into symptoms and clinical signs: Commonly symptoms are:

1. variable loss of central vision which usually recovers within 2-6 weeks
2. dull aching pain in the region of the eye, aggravated by movement, especially elevation

On examination:

1. visual field defect - most commonly a central scotoma
2. loss of colour vision
3. relative afferent pupillary defect
4. reduced visually-evoked response

Ophthalmoscopically:

1. the optic disc normal in retrobulbar neuritis
2. in papillitis, the disc may be swollen, with blurred margins and filling of the physiologic cup; the disc is hyperaemic with distension of retinal veins. The surrounding retinal oedema may be extensive and flame shaped haemorrhages may be observable on the surface of the disc and the adjacent retina.

Question 4

optic neuritis: ix

Answer 4

fundoscopy

Question 5

optic neuritis: diagnosis + rx

Answer 5

• Sudden loss of vision is an ophthalmological emergency and requires immediate referral to the eye emergency department.
• The treatment of optic neuritis is directed toward the underlying cause. Systemic corticosteroids are unproven except in cases of papillitis in which there is minimal evidence of collagen vascular disease or other signs of multiple sclerosis.
• The majority of patients under the age of 45 years recover normal visual acuity within 2 months. Older patients recover less well and there may be evidence of optic atrophy.
• If recovery is poor, a compressive lesion must be excluded, especially if both eyes are effected.
• Attacks are cumulative. Significant visual loss accompanies repeated episodes of neuritis.
• If a person has an episode of isolated optic neuritis, confirmed by an ophthalmologist, refer them to a consultant neurologist for further assessment

>>>>>Optic neuritis due to MS: good – gradually improves (dys-mo) – relative loss of colour vision

Question 6

trigeminal neuralgia definition

Answer 6

Trigeminal neuralgia is a pain syndrome characterised by severe unilateral pain.

The vast majority of cases are idiopathic but compression of the trigeminal roots by tumours or vascular problems may occur

often described as ‘worst pain ever’

Question 7

trigeminal neuralgia: aetiology

Answer 7

Exact cause of trigeminal neuralgia remains unclear (1)

most cases are considered idiopathic (1)

many are associated with demyelination of the trigeminal nerve. This can be due to

vascular compression of the nerve root by aberrant or tortuous vessels

multiple sclerosis or tumours affecting the nerve root

Question 8

trigeminal neuralgia: s/s

Answer 8

• a unilateral disorder characterised by brief electric shock-like pains, abrupt in onset and termination, limited to one or more divisions of the trigeminal nerve
• the pain is commonly evoked by light touch, including washing, shaving, smoking, talking, and brushing the teeth (trigger factors), and frequently occurs spontaneously
• small areas in the nasolabial fold or chin may be particularly susceptible to the precipitation of pain (trigger areas)
• the pains usually remit for variable periods

~~~~~~~~~~~~~~~

Trigeminal neuralgia presents with brief electric shock-like pains, abrupt in onset and termination, limited to the distribution of one or more divisions of the trigeminal nerve (1).

site

• pain is unilateral in the distribution of the trigeminal nerve, mandibular is singularly affected in 20% of cases; the mandibular and maxillary divisions together in 40% of cases; and all three affected in 15% of cases, it is rare for the ophthalmic division to be affected by itself
• it is bilateral in only 3% of patients and rarely is the pain active on both sides at the same time

periodicity

• episodic and sudden onset of pain, lasting a few seconds to minutes and stopping suddenly, with many attacks a day
• there is a refractory period between each attack
• pain might then go into remission for a few weeks or months; pain free intervals gradually shortens between episodes with time (pain often gets longer with time)

character

• electric shock like, sharp, shooting

severity

• very severe attacks, pain may be so severe that the patient will only be able to point to the site of the pain and not be able to touch the site
• can get milder when patients are given drug treatment

factors affecting pain

• pain can be provoked by light touch to the face, eating, cold winds or vibrations
• repeated stimulation may alleviate symptoms temporarily and permit pain free activity, e.g. to eat food

associated factors

• rarely associated with history of other chronic pain or migraine. Some forms have more continued aching background pain after main attack. Rarely associated with autonomic features

Question 9

trigeminal neuralgia ddx

Answer 9

• the differential diagnosis facial pain includes (1):
  
  • trigeminal neuralgia
  • atypical facial pain
  • trigeminal neuropathy - persistent pain; associated sensory loss
  • dental causes e.g. dental abscess - localized; related to biting or hot or cold foods; visible abnormalities on oral examination
  • local causes of eye pain
    
    • glaucoma, orbital cellulitis
  • post herpetic facial pain - continuous pain; tingling; history of zoster; often first division
  • local injury to the trigeminal nerve
    
    • facial trauma
    • fractures of the facial bones
    • sinus surgery
  • tumor infiltration of the nerve anywhere anterior to the gasserian ganglion
  • glossopharyngeal neuralgia - pain in tongue, mouth, or throat; brought on by swallowing, talking, or chewing
  • vascular causes of facial pain
    
    • temporal or giant-cell arteritis - persistent pain; temporal; often bilateral; jaw claudication
    • migraine - pain in tongue, mouth, or throat; brought on by swallowing, talking, or chewing
  • autoimmune disorders
    
    • systemic lupus erythematosus
• it is important to exclude other causes of trigeminal neuropathy (secondary trigeminal neuralgia) before reaching what is essentially, a clinical diagnosis.

Question 10

trigeminal neuralgia: ix

Answer 10

MRI: exclude 2ry cause

Question 11

trigeminal neuralgia: medical mx

Answer 11

The aim of treatment for trigeminal neuralgia is pain relief

• medical management
  
  • carbamazepine
    
    • only drug licensed for trigeminal neuralgia in the UK
    • 70% of patients with trigeminal neuralgia have good initial pain control with carbamazepine (1)
    • side effects include: tiredness and poor concentration and there is a high risk of drug interactions.
  • oxcarbazepine
    
    • a keto derivative of carbamazepine
    • recommended as second line medicine
    • has shown similar efficacy to carbamazepine
  • baclofen
    
    • useful in multiple sclerosis and when combined with carbamazepine
  • lamotrigine
    
    • can be used with carbamazepine or oxcarbazepine

Question 12

trigeminal neuralgia: surgical mx

Answer 12

• surgical management
  
  • patients with poor control of pain while taking medications, may need surgical intervention.
  • surgical treatment falls in to two categories
    
    • palliative destructive procedures
      
      • controlled destruction of trigeminal nerve root with the aim to relieve pain
      • heat (radiofrequency lesioning), chemicals (with a viscous glycerol called glycerol rhizolysis), and mechanical (by crushing the nerve against surrounding bone and dural reflections called balloon compression) procedures are used
      • can be performed for all causes of trigeminal neuralgia
    • microvascular decompression:
      
      • aims to decompress the trigeminal nerve, and deals with the cause of trigeminal neuralgia in the 95% of cases not caused by other lesional causes (1)

Question 13

trigeminal neuralgia: prognosis

Answer 13

• The prognosis of trigeminal neuralgia is poor.
• Remissions may last for several years between attacks. The longer the individual has had the condition, the more frequent the episodes become.

Question 14

bells palsy: definition

Answer 14

• Bell’s palsy may be defined as an acute, unilateral, idiopathic, facial nerve paralysis.
• The aetiology is unknown although the role of the herpes simplex virus has been investigated previously.
• The peak incidence is 20-40 years and the condition is more common in pregnant women.
• it is a lower motor neurone palsy usually diagnosed by exclusion.
• Typically, presentation is with facial distortion, loss of taste, hyperacusis and a watery eye.

Question 15

bells palsy: aetiology

Answer 15

• Causes of facial nerve palsy:
• Bell’s palsy (70% of cases)
• Ramsay hunt syndrome
• Infection: TB, Viruses (HIV, Polio), meningitis, Lyme disease
• Brainstem lesions: stroke, tumour, MS
• Cerebello-pontine angle: acoustic neuroma, meningioma
• Systemic disease: DM, sarcoid, guillian-barre
• ENT: Parotid tumours, otitis media, cholesteatoma

Cranium: trauma to the base of skull, intracranial hypotension

Question 16

bells palsy: s/s

Answer 16

The clinical features of Bell’s palsy are varied:

• usually of sudden onset and complete within 24 hours; less frequently, the condition is progressive developing over a course of less than 4 days
• almost always unilateral
• onset may be preceded by post-auricular pain which develops over a 48 hour period
• there is paralysis of the upper and lower facial muscles
  
  • the eyebrow droops and the wrinkles of the brow are smoothed out; frowning and raising the eyebrows are impossible
    
    • if there is an upper motor neurone lesion affecting the facial nerve then the ability to wrinkle the brow is preserved; in Bell’s palsy this ability is lost
  • the eye cannot be closed. When asked to close the eyes and show the teeth, the eyeball rotates upwards and outwards - Bell’s phenomenon.
• the lower lid is everted. Tear production (lacrymation) is decreased.Eye irritation often occurs due to lack of lubrication and constant exposure.The eye may appear to tear excessively due to loss of lid control, which may cause tears to spill freely from the eye (3)
• the mouth sags and the patient dribbles. The patient is unable to blow out the cheeks. The lips cannot be pursed and whistling is impossible. The effects tend to be more pronounced in the elderly.
• sensory component of the corneal reflex is intact - trigeminal nerve - but motor component is lost - facial innervation of orbicularis oculi.
• involvement of the chorda tympani nerve results in loss of taste
• hyperacusis develops if the lesion of the facial nerve extends to above the point at which the branch to the stapedius muscle is given off

Question 17

bells palsy: ddx

Answer 17

• Bell’s palsy must be distinguished from other causes of facial palsy - see facial palsy for more information
• the differential diagnosis includes:
  
  • nuclear (peripheral) causes (1)
    
    • lyme disease
      
      • this is more likely if the facial weakness is bilateral
      • history of tick exposure, and arthralgias
      • look for a rash
    • otitis media
      
      • suppurative otitis is excluded by examining the ear
      • there is gradual onset ear pain, fever, and conductive hearing loss
    • Ramsay Hunt syndrome
      
      • herpes zoster may produce an acute facial weakness but is accompanied by a rash within the auricle - geniculate herpes - or on the palate, pharynx, face, neck or trunk
      • there may be a pronounced prodrome of pain
    • sarcoidosis
      
      • sarcoidosis affecting the parotid gland is suggested by recurrent facial palsy
      • facial weekness is often bilateral
    • Guillain-Barré syndrome
      
      • facial weekness is often bilateral
    • HIV infection
      
      • more likely if the facial weakness is bilateral
      • look for lymphadenopathy
    • tumours
      
      • cholesteatoma, parotid gland tumours
  • supranuclear (central) causes (2)
    
    • multiple sclerosis
      
      • multiple sclerosis should be considered if the palsy is unilateral, in a young adult, is painless, and resolves in 2-3 weeks
    • stroke
    • tumours
      
      • metastases or primary brain tumours
      • history of cancer
      • look for mental status changes
• Horner’s syndrome and IIIrd nerve palsies produce a ptosis

Question 18

bells palsy: mx

Answer 18

• general measures - reassurance is important. The patient may be worried that there has been a stroke or that there will be permanent disfigurement.
• recommended that prednisolone 1mg/kg for 10 days should be prescribed for patients within 72 hours of onset of Bell’s palsy. Adding in aciclovir gives no additional benefit
• eye care is important - prescription of artificial tears and eye lubricants should be considered + :
  • Dark glasses
  • Tape closed @ night
• treatment of sequelae - if recovery has not occured after a reasonable time - 10 months - then the lesion may be considered permanent and plastic surgery should be considered to correct any deformity. Surgery to cut the tympanic nerve and prevent crocodile tears - i.e. tears from the affected eye on eating as a result of faulty reinnervation in the autonomic system may also be necessary.

Question 19

bells palsy: prognosis

Answer 19

• Incomplete paralysis: recovers completely w/iwks
• Complete: 80% get spontaneous full recovery – delayed ~3mo
• Remainder have delayed recovery or permanent
• neurological / cosmetic abnormalities

Question 20

Ramsay hunt syndrome:

Answer 20

Definition: Reactivation of VZV in geniculate ganglion of CNVII

Epidemiology: Incidence - ~5-100000, age - >60

Clinical features:

· Preceding ear pain or stiff neck

· Vesicular rash in auditory canal ± TM, pinna, tongue, hard palate (no rash = zoster sine herpete) or iris

· Ipsilateral facial weakness, ageusia, hyperacusis,

· May affect CN8 → vertigo, tinnitus, deafness

Mx: If Dx suspected give Aciclovir+ prednisolone w/I first 72h

Prognosis: Rxed w/i 72h: 75% recovery, Otherwise: 1/3 full recovery, 1/3 partial, 1/3 poor

Question 21

bells palsy: complications

Answer 21

• Aberrant Neural Connections
• Synkinesis: e.g. blinking causes up-turning of mouth
• Crocodile tears: eating stimulates unilateral lacrimation, not salivation

Question 22

forehead sparing + UMN/LMN lesions

Answer 22

• Upper motor neuron lesion: upper part of the face is spared
• Lower motor neuron lesion: both upper and lower parts of face affected