Myesthenia Gravis/CPEO

aetiology

MG - aetiology

• autoimmune disease

• disorder of neuromuscular junction due to reduction of acetycholine receptors sites and motor end of plate

• causing weakness in skeletal muscles.

• Mechanism: Autoantibodies block or destroy acetylcholine receptors at the neuromuscular junction, impairing muscle contraction.

• Affected Areas: Eyes, face, neck, limbs, and respiratory system.

• Progression: Muscle weakness worsens with activity, improves with rest.

Types of MG

11. Autoimmune Myasthenia (most commom

12. Neonatal Myasthenia – transient, due to maternal antibodies.

3. Congenital Myasthenia – genetic, not autoimmune.

Subtypes:

• Ocular MG – affects eye muscles (ptosis, diplopia).

• Generalized MG – includes eye, facial, neck, limb, and throat muscles.

Most common in women ~40 years and men >60 years.

symp

Symptoms

-          Muscle weakness, fatigue

-          Ocular: dip, ptosis

-          Facial dysphagia: swallowing issues

-          Limb weakness

-          Respiratory: SOB

-          Variability symptoms

-          Worse in hot temp

Causes

• Autoimmune: Faulty immune response; thymus gland involvement.

• Congenital: Genetic mutation.

• Neonatal: Transferred antibodies from mother.

Pathophysiology

• Normal: Nerve releases acetylcholine → binds to muscle receptor → muscle contracts.

• MG: Antibodies block receptors → impaired signal transmission → muscle weakness.

risk factors and complications

-          Autoimmune disease – lupus

-          Thyroid disorder

-          Triggers: sx, infection

Complication

-          Respiratory failure

-          Emotional stress, depression

-          Physical limitation

-          Over 40yrs

-          Bilat ptosis

-          TED, diabetes

-          Diplopia

-          CT: Hyper T – IR isolated

thymus gland & diagnosis

hymus Gland Connection

• Thymic hyperplasia: In 2/3 of cases.

• Thymoma: Tumors in 10% (may be benign or cancerous).

Diagnosis

• Physical exam & history.

• Tests:

  • Blood tests: ACh receptor or MuSK antibodies.

  • MRI/CT: Check thymus for tumors.

  • EMG: Measures nerve-muscle communication.

MG Classification (Severity):

1. Class I: Ocular only.

2. Class II: Mild generalized.

3. Class III: Moderate generalized.

4. Class IV: Severe.

5. Class V: Respiratory involvement (needs ventilation)

tx

TX

-          No cure

-          Medication

o    Monoclonal antibodies

o    Immunosuppressant

o     Corticosteroid

o    Anti ACH drug

Procedure

-          Plasmapheresis – remove harmful antibodies

-          IVIG/SCIG – donor antibodies

-          Thymectomy – removal thymus gland  

-          Anticholinesterase

-          Mestinon

Sx

-          BT sm dev

-          Ptosis: props, brow suspension, tarsal resection

Optical

-          Prism or occlusion – symptomatic

Lifestyle

-          Mod exercise

-          Balanced diet

Multidisciplinary team

 

Test

-          Cogan lid twitch – upward lid twitch after downgaze

-          Ice pack test - ↓ in ptosis

-          Fatigue testing – sustained upward gaze = worsen ptosis

-          Tensolin – hospital injection imp ptosis

-          ACH test – blood test confirmation + musk antibodies  

-          Simpson test- + ve

-          EMG- ↓ firing - SFEMG

-          Hess: variable

-          MRI/CT: hyperplasia/ thymoma

-          Anti- musk test

-      

inv

Investigation

-          Ch: fatigue, dip, ptosis int

-          VA: amblyopia risk

-          CT: decomp phoria, manifest dev

-          OM: variable, eye signs

o    IR paresis: mimic INO

-          Special sign

o    Cogan lid twitch

o    Upper lid retraction

-          Fatigue test

o    IR palsy

-          Sleep test

o    Radiodiagnosis

o    ACH test

o    Single F EMG

o    Musk antibodies

DD

-          Anything

-          Aberrant regeneration = ptosis, variability, restrictions

o    BUT MG NOT CONTROL PUPIL movements

o    If findings stable = AR

CPEO

Overview

-          Benign, progressive, ocular disorder

-          Progressive to full CPEO w no remissions

Onset

-          Age – around 30yrs – hereditary

-          Childhood – rapid deterioration by 5yrs

-          Self-limiting

Aetiology

-          Primary myopathy of EOM

-          Inherited e.g. multiple mutation

CPEO - INV

Investigation

-          Bilateral ptosis/ weak orbicularis

-          AHP – chin elevation

-          X or sm V

-          Fibrosis late

-          +VE FDT

-          Slow progressive limitation of OM

-          Ptosis props

Clinical feature

-          CH: pharyngeal weakness, deafness, dementia + optic atrophy

-          Diplopia

CT: HypoT – XT

AHP – chin elevation

Ptosis

-          Unilat – becomes bilat

-          No LPS function

-          Frontalis o/a

-          Absent bells p

CPEO - mx

Mx

-          Ptosis props – complete bilat ptosis

-          Poor Bells – corneal protection

-          Brow suspension – or ptosis sx – if stable

-          Prism/ occlusion for dip

Sx when stable

-          Cosmetic/ AHP

-          Transposition – IR or SR resection

-          LR recession + MR resection

-          BT – sm angle dev