Lecture 30 Myogenic palsies Flashcards
What is myasthenia gravis?
what muscles are effected?
autoimmune condition
arises from severely weak muscle
*Only striated muscle affected
*effects all of the striated muscle or affects only some specific groups.
Order of frequency is:
*extra ocular, facial, bulbar, neck, limb, girdle, distal limb and trunk.
*Inter costal (respiratory) muscles are affected the disease may prove fatal
Does myasthenia gravis effect females or males more?
- Ages 20-30: females>males
- Ages 50-60: males>females
What is the aetiology of MG in paeds?
1.Neonatal
-born to myasthenic mother
-disease is self-limiting (6 weeks approx.)
2.Congenital
-infants born to non-myasthenic mothers
3. uvenile
-Develops in infancy
-More spontaneous remissions than adults
What is the aetiology of MG in adults?
- Ocular myasthenia
-Limited to eye muscles
-If still limited to muscles after 2 years, highly unlikely to become generalised - Mild to moderate (generalised)
-Often slow onset of symptoms
-Doesn’t effect respiratory muscles - Acute fulminating (generalised)
-Rapid onset
-Early involvement of respiratory muscles - Late severe (generalised)
-Severe
-Develops 2 years after first signs of muscle weakness - Drug related
-D-Pencillamine induced myasthenia
-This drug is used in rheumatoid arthritis, systemic lupus
Why are the muscles weak in MG?
-MG px develop antibodies to the receptor sites at the muscle end plate
-antibodies prevent Ach from binding and this reduces neurotransmitter take-up
-Ack continues to be released until supply is exhausted and muscle fatigues
What are the systemic symptoms and signs of MG?
General
*Fatigue
*Lack of energy
Limb girdle
*Difficulty getting out of a chair
*Difficulty climbing stairs
Facial
*Lack of facial expression
Bulbar
*Problems with speech
Respiratory
*Problems breathing
What are the ocular signs and symptoms of MG?
Ptosis
*marks onset of disease in 70% of cases
Diplopia
*marks onset of disease in 70% of cases
Orbicularis weakness
*ask them to close eyes and scrunch up lids tight.
*Gently try to pen up there eye. This will be easily done in these px.
Describe the ptosis you will get in someone with MG?
*Usually bilateral
*Often asymmetrical
*Increases with fatigue (px may say lids get lower throughout the day)
*Frontalis over-action seen to elevate eye (scrunching forward)
*Occasional lid retraction in attempt to elevate the more ptoic eye
What must you ask to investigate ptosis?
How can you check if the ptosis is due to MG?
does it vary across the day?
*Request px to elevate their eyes for 1-2 minutes and look at pen torch
*If Severity of ptosis increases after this in PP, suspect MG
-ice pack test: ice pack is placed on both eyelids for 2 minutes.
-if ptosis improves-strong indication of ptosis
What is cogan’s lid twich?
*Request patient to depress their eyes for 15 seconds and then look in PP
*Lid movement follows eyes movement on depression
*The lid initially moves above its previous level when eyes return to PP
*Lid then returns to its original ptotic position.
What is Gorelick’s sign?
*Done when px has asymmetric ptosis
*Examiner holds up the more ptotic lid
*Innervational drive to both eyes is reduced
*Ptosis on the less affected side starts to increase
How can you investigate diplopia in MG?
does double vision vary across the day?
*Variable diplopia (horizontal to vertical)
*Diplopia increases as muscles fatigue
*Mimics any type of muscle palsy (L-R palsy now IR palsy)
*May mimic internuclear ophthalmoplegia (INO)
*May mimic gaze palsy
How can you check for orbicularis weakeness?
- Can usually close eyes
- May not be able to bury eye lashes
- Unable to stop examiner opening eyes with gentle pressure
When must you suspect MG?
*Ocular symptoms increase with fatigue
*Systemic symptoms increase with fatigue
*Diurnal variation symptoms worse as the day progresses
*Weakness increases after exercise
*In the earlier stages the weakness maybe intermittent
VARIABILITY IN SYMPTOMS
How can you detect MG?
-receptor antibodies (detected in bloodtest)
-enlarged thymus gland
-tensilon test (short-acting anticholinesterase is injected)
What disease is associated with MG?
thyroid eye disease (5%)
What is the systemic treatment of MG?
what is the ocular treatment of MG?
*Longer acting anticholinesterases pyridostigmine (mestinon)
*Immunosuppressive agents such as systemic steroids
*Plasmaphoresis to reduce level of circulating antibody or intravenous immunoglobulin
*Thymectomy (20%-60% of patients can enter remission)
Ocular treatment of Myasthenia Gravis
Ptosis props.
* Contact lens
Occlusion
* Blenderm on glasses
* Frosted lens
* Occlusive contact lens
Surgery
* Contraindicated unless stable for a long time
What is lambert-eaton rooke syndrome (LERS)?
what disease is it associated with?
when does risk reduce?
why should you monitor closely for first 2 years?
*Defect is presynaptic.
*Proximal limb weakness
*Association with small cell carcinoma
- After having LERS for 2 years, risk reduces
- Monitored closely for first 2 years for cancer
What are the characteristics of LERS?
*Limb weakness
*The muscles resting action potential is reduced
*Muscles action potential increases after repetitive stimulation
*Dry mouth
*Ptosis in approximately 50% of cases
*Extraocular muscle involvement very unusual
*Response to tensilon is unpredictable.
What is the management of LERS?
-exclude malignancy
-guanidine hydrochloride
-ptosis props
What are the characteristics of chronic progressive external ophthalmoplegia?
*Progressive symmetrical loss of ocular motility
*Progressive symmetrical bilateral ptosis
*Loss of Bell’s reflex (i.e. eyes don’t roll upwards when lids are closed)
*If the loss is not symmetrical, px may not complain of diplopia
*Orbicularis weakness
*Pupillary responses normal as smooth muscle not affected
-end stage: eyes are severely mechanically restricted “FROZEN EYE”
What is the aetiology of CPEO?
*It is the commonest of the mitochondrial myopathies.
*CPEO is often associated with Kearne-Sayre-Daroff syndrome.
Kearne-Sayre-Daroff syndrome (Features):
* Onset before 20 years old.
* Fine pigmentary retinopathy
* Heart conduction block
What is the management of CPEO?
If complains of diplopia:
* Prisms
* Occlusion
* Occlusive contact lens
* Blenderm
* Frosted glasses
Surgery if eye is grossly eccentrically fixated.
What are the characteristics of orbital myositis?
*Inflammation of one or more of the extra-ocular muscles
*Usually unilateral
*Occasionally bilateral
*Proptosis. Measured using an exophthalmometer.
*Pain
*Lid oedema
*photphobia
*Conjunctivitis with or without chemosis
*limitation of extra-ocular movements:
-Paretic in direction of muscle action
-Mechanical in the opposite direction
What is the aetiology of orbital myositis?
what is the dd?
what is the management?
-autoimmune disorders
*orbital cellulitis
*orbital abscess
*hematoma
*Grave’s disease (thyroid eye disease)
*Tumours
-systemic steroids
What is Rhabdomyosarcoma?
what are the signs?
what is the management?
*Highly malignant tumour of the striated muscle
*60 children/year in the UK
*70% occur during first decade (boys >girls)
*May present with a tropia in early stages
*Limitation of eye movement in early stages
*Rapid (weeks) tumour growth will lead to proptosis
-rapid diagnosis and treatment
-radiotherapy and chemotherapy
