Myasthenia gravis. David Hilton-Jones Oxford Neuromuscular Centre

Size: px

Start display at page:

Download "Myasthenia gravis. David Hilton-Jones Oxford Neuromuscular Centre"

Tracey Dixon
5 years ago
Views:

1 Myasthenia gravis David Hilton-Jones Oxford Neuromuscular Centre SWIM, Taunton, 2018

2 Myasthenia gravis Autoimmune disease Nature of Role of thymus

3 Myasthenia gravis Autoimmune disease Nature of Role of thymus Why? Thymoma (paraneoplastic) Molecular mimicry Immune diathesis Unknown

4 Myasthenia gravis Prevalence 1:10,000 1:5 GPs 10:DGH neurologist

5 Myasthenia gravis Management Outcome Local neurologist Specialist referral Second opinion Difficulties with management

6 Myasthenia gravis The neuromuscular junction What is it? How does it work?

10 Ion channels and their disorders at the neuromuscular junction Potassium Calcium Nerve terminal Acetylcholine Threshold Depolarisation of muscle membrane that leads to contraction in muscle fibre if it exceeds the firing threshold Target Autoimmune disease Genetic disease Acetylcholine receptors Myasthenia gravis Acetylcholine receptor deficiency Slow channel syndrome, fast channel syndrome Muscle specific kinase Generalised myasthenia gravis Not known without AChR antibody Voltage gated calcium channels Lambert Eaton myasthenic syndrome Not known Voltage-gated potassium channels Acquired neuromyotonia Episodic ataxia with myotonia

11 Fatiguability Clinical features

12 Clinical features Fatiguability Weakness At onset Extraocular muscles (75%) Ptosis Diplopia

13 Clinical features Fatiguability Weakness At onset Extraocular muscles (75%) Ptosis Diplopia Bulbar (20%) Dysphagia (+ chewing) Dysarthria

14 Clinical features Fatiguability Weakness At onset Extraocular muscles (75%) Ptosis Diplopia Bulbar (20%) Dysphagia Dysarthria Proximal limb (5%)

15 Clinical features Fatiguability Weakness Over time (75% - within 2 years) Bulbar Dysphagia Dysarthria Facial weakness

16 Clinical features Fatiguability Weakness Over time (75% - within 2 years) Bulbar Dysphagia Dysarthria Facial weakness Limb Proximal Distal (rare)

17 Clinical (gestalt) Diagnosis

18 Diagnosis Clinical (gestalt) Serum antibodies Generalised myasthenia AChR ELISA (80%) Low-affinity AChR (10%) MuSK (10%) Seronegative (5%)

19 Diagnosis Clinical (gestalt) Serum antibodies Generalised myasthenia AChR ELISA (80%) Low-affinity AChR (10%) MuSK (10%) Seronegative (5%) Ocular myasthenia AChR (50%) MuSK (<5%) Seronegative 50%

20 Diagnosis Neurophysiology Decrement

21 Diagnosis Neurophysiology Decremental response Supramaximal, 3Hz, record CMAP

22 Diagnosis Neurophysiology Decrement Generalised myasthenia ~80% Ocular myasthenia very low

23 Diagnosis Neurophysiology Single-fibre EMG (limited availability) Orbicularis oculi (not EOM) Limb Abnormal in ~80% of those with ocular symptoms Abnormal in >80% of those with generalised MG

24 Diagnosis Tensilon test False positives False negatives

25 Other investigations Thyroid function Chest scan Thymoma in ~10% (? All AChR positive) To exclude thymoma, not to show hyperplasia

26 Thymus radiological-pathological correlations in myasthenia gravis the relevance in clinical practice Klimiec et al 2018 Muscle & Nerve (In press) 1) All newly presenting patients with MG should have thymus imaging. (Generalised and ocular) 2) The decision to offer thymectomy in those without thymoma should be based on clinical and immunological grounds, not the radiological appearance of the thymus

27 Treatment of MG Failure to understand the principles, and probably more frequently failure to apply them, of the long-term treatment of MG are major causes of persisting morbidity and the risk of episodes of myasthenic crisis

28 Treatment of MG Failure to understand the principles, and probably more frequently failure to apply them, of the long-term treatment of MG are major causes of persisting morbidity and the risk of episodes of myasthenic crisis

29 Guidelines Myasthenia gravis: Association of British Neurologists management guidelines Sussman J, et al Practical Neurology Mark (Following thymectomy trial)

30 Treatment Pyridostigmine Immunotherapy Steroids Second-line agents (AZA, Mycophenolate mofetil, CICLO, MTX) Rituximab Thymectomy (IVIg & plasma exchange)

31 Pyridostigmine Mode of action Too little Too much (<8 tablets (60mg) a day) Don t procrastinate

32 Prednisolone Highly effective Too little Too much/long Bones

33 Second-line agents Azathioprine Proven efficacy Safe in pregnancy 10% intolerant (N.B. TPMT)

34 Second-line agents Azathioprine Proven efficacy Safe in pregnancy 10% intolerant Ciclosporin Safe in pregnancy Kidneys Blood pressure

35 Second-line agents Mycophenolate mofetil Proven inefficacy! Not safe in pregnancy Well-tolerated

36 Second-line agents Mycophenolate mofetil Proven inefficacy! Not safe in pregnancy Well-tolerated Methotrexate Not safe in pregnancy (males and females)

37 Rituximab

38 Potential advantages of RTX Easy to give Standard dose (2 x 1gm) Repeated if needed Relatively cheap ~ 5,000 Bioequivalent < 1,000

39 Problems with RTX Unlicensed Unfunded

40 Problems with RTX Unlicensed Unfunded Evidence it actually works!!

41 Evidence of efficacy Response of myasthenia gravis to rituximab in a patient with lymphoma: first report Gajrav A & Grethlein SJ Blood 2000;96:237

42 Evidence of efficacy Response of myasthenia gravis to rituximab in a patient with lymphoma: first report Gajrav A & Grethlein SJ Blood 2000;96:237 The patient experienced marked improvement in her muscle weakness and fatigability by history and physical examination. Her longstanding diplopia also resolved It may be an additional therapy in management of myasthenia gravis and should be studied further

43 Evidence of efficacy The role of rituximab in the treatment of myasthenia gravis Benveniste O & Hilton-Jones D European Neurological Review 2010;5: Efficacy and safety of rituximab for myasthenia gravis: a systematic review and meta-analysis Iorio R, et al Journal of Neurology 2015;262:

44 Evidence of efficacy Rituximab treatment of myasthenia gravis: A systematic review Tandan R, et al Muscle & Nerve 2017;56:

45 Conclusion RTX works well for some people, but not all MuSK MG may be more responsive Generally safe 2 cases of PML Need prospective studies Paris America

46 Proposal RTX should be available for use in specialist MG centres for patients in whom conventional approaches have failed

47 Opportunities Detailed collation of cases will provide prospective evidence of efficacy Cost saving IVIG/PEX 12,000/admission Daily cost of ITU > 2,000

48 NHSE Application for the use of Rituximab in Myasthenia Gravis An application which, if successful, will permit us to develop a policy!

49 Thymectomy

50 Thymectomy trial

51 Thymectomy Trial 36 centres Age range 18- (60) 65 yrs Non-thymomatous MG Class II-IV disease Duration < (3) 5 yrs Median sternotomy

52 Statistical error

53 3 year Outcome Thymectomy No thymectomy 6.15 QMG mg Pred (A/D) 54mg 17% AZA 48% 9% Hospital 37%

54 3 year Outcome Thymectomy No thymectomy 6.15 QMG mg Pred (A/D) 54mg 17% AZA 48% 9% Hospital 37% Thymectomy improved clinical outcomes over a 3-year period in patients with nonthymomatous myasthenia gravis

55 Traditional approach Pyridostigmine Steroids + azathioprine Thymectomy Sternal-splitting VATS

56 Current guidelines approach Pyridostigmine Consider thymectomy Prednisolone 2 nd line immunosuppressant IF prednisolone fails or intolerant or comorbidity Don t hesitate to refer to MG specialist

57 Current guidelines approach Pyridostigmine Limited benefit Limited trial Consider thymectomy AChR +ve, recent onset, up to 65 yrs Even in purely ocular disease (75% rule) Prednisolone Too little too brief 2 nd line immunosuppressant IF prednisolone fails or intolerant or comorbidity Azathioprine Don t hesitate to refer to MG specialist

58 Myasthenia gravis Relatively common Diagnosis Easy if ocular presentation More difficult if bulbar (elderly) Highly treatable But patient dissatisfaction? Thymectomy likely to become more frequent? Rituximab

Myasthenia gravis. Page 1 of 7

Myasthenia gravis. Page 1 of 7 Myasthenia gravis What is myasthenia gravis? Myasthenia gravis (sometimes abbreviated to MG) is a chronic, autoimmune condition that causes muscle weakness and excessive muscle fatigue. It is rare, affecting