Acquired neuropathies chap:23

1. Acquired neuropathieschap:23 Alireza Ashraf, M.D. Associate Professor of Physical Medicine & Rehabilitation Shiraz Medical school

2. GBS • In one report earliest feature: proximal nerve edema+ degeneration myelin sheath within first week of illness • In other study prominent perivascular inflammation in spinal root ,ganglia ,cranial nerve and randomly along peripheral nerve

3. Acute inflammatory demyelinating polyradiculoneuropathy (AIDP) • Most common cause of acute generalized weakness • Annual incidence:1-4/100000 general population • Slight male predominance • Peak age of onset in the 3-4 decade of life • 60-70% of patient note some form of Acute illness 1-3 wk before onset of neurologic symptom (C.j 32%-CMV 13%-EBV 10%- M.pnumonia 5%)

4. most patient initially note Tingling and numbness in distal of lower limb and shortly thereafter in the distal upper limb • Large fiber modality (vibration ,touch , position) more severly affected than small fiber modality (pain , temperature) • A few patient present only with sensory symptom but EDX sign of motor involvement are typical • Major complaint of most patient : progressive weakness

5. Mild facial weakness in 50%of patient during course of illness. • Occasionally a descending presentation with onset in the cranial nerve and progress to the arm and leg • External urethral and anal sphincter usually spared .although may be involved in severe disease.

6. Autonomic instability is common in AIDP • Neonatal GBS : in infant of a mother with GBS due to Ab crossing the placenta. • The disease usually progresses over the course of 2-4 wk. • Progression of symptom and sign for over 8 wk excludes GBS and suggest the diagnosis of CIDP. • Respiratory failure in 30% • Neck flexion ,extension and shoulder abduction correlate well with diaphragmatic strenght and thus important to follow closely.

7. Most patients gradually recover satisfactory function over several months • The mortality rate about 5% • Patient die result of RDS ,aspiration Pneumonia ,pulmonary embolism ,arrhythmia and sepsis

8. Risk factor for poor prognosis (slower and incomplete recovery): • age greater than 50-60years, • abrupt onset of profound weakness, • need for mechanical ventilation, • distal CMAP Ampl less than 10-20% of normal.

9. Lab feature • Elevated CSF protein accompanied by no or only a few mononuclear cell is the characteristic laboratory findings and evident in over 80% of patient after 2 wk. • In patient with CSF pleocytosis of more than 10 Lymphocytes (cell count >50), AIDP like neuropathies related to lyme disease, recent HIV infection, sarcoidosis need to be considered. • Elevated liver function test evident in many patient. In such cases important to evaluate for viral hepatitis (A,B,C),EBV, CMV • Antiganglioside Ab particularly anti GM1 correlates well with c.j infection.

10. histopathology • The entire peripheral motor and sensory nervous system including cranial nerve can be involved from the most proximal aspect of the ventral and dorsal root to the terminal region of the intramuscular and sensory nerve fibers. • An initial preference for the nerve root region ,areas where peripheral nerve commonly entrapped and the motor nerve terminals.

13. Motor NCS • Electrophysiologic hallmark of demyelination: • prolonged distal latency • Slow NCV • Temporal dispersion • Conduction block • Prolonged F-wave latency

15. A hallmark is the asymmetric and multifocal character of the EDX abnormality • Always perform F-wave study in both upper and lower limb in patients suspected of having AIDP because of early predilection for the proximal nerve segments and spinal roots.

17. In patient with rapid recovery ,particularly after PE or IVIG the improved clinical status probably result from coduction block resolution rather than remyelination or regeneration of the axons. • Two important caveats about conduction block: • First, 5-7day after acute axonal loss, it is impossible to distinguish between axonal loss and conduction block • Second,in acute disease small reduction in CMAP Ampl may be result from conduction block; however ,in more chronic disease or later in acute disease alteration in conduction velocity may result in pseudocoduction block.

18. Examination of the pherenic and facial nerve may be interest in AIDP. • Facial and supraorbital nerve evaluated with direct facial nerve stimulation and blink reflex. • Maximum degree of motor conduction abnormality occure within 3-8 wk.

19. Early abnormalities of distal CMAP Ampl and latency and F-wave reflect the early predilection for involvement of the proximal spinal roots and distal motor nerve terminals in AIDP.

20. There does not appear to be a correlation between the nerve conduction velocity or distal motor latency and clinical severity of the neuropathy ,although distal CMAP Ampl less than 10-20% normal are associated with a poorer prognosis.

21. S-NCS • Upper limb SNAP particularly median nerve affected more severly and earlier than sural SNAPs. • Unlike most axonopathies , in which the earliest and most severe abnormalities involve the distal lower limb nerve (sural SNAP), demyelinating disease are just as likely to affect the median and ulnar SNAPs.

22. It can take 4-6wk for SNAP abnormalities to peak. • The parameter most adversely affected is SNAP Ampl. • Reduced SNAP Ampl can result from secondary axonal degeneration ,conduction block or phase cancelation. • With a pure sensory presentation , other Disorders (acute sensory neuronopathy or ganglionopathy) must be ruled out.

23. Needle EMG • EMG in patients with AIDP is primarily adjunctive to explore the possibility of other disease entities. • Earliest finding a reduced number of normal- appearing MUAP firing at rapid rate. • Fib and psw may first be seen between wk 2- 4,peaking at about 6-15wk;maximize earlier in proximal muscle than in distal muscle. • Myokymia can be detected especially in facial muscles.

24. Autonomic testing • Autonomic instability can be assessed by measuring the EKG R-R interval variation. • A alternative method is SSR.

25. Plasma Exchange • reduced the time necessary to improve one clinical grade, time to walk unaided, time on a ventilator and percentage of patient improving after 1-6 month. • Total amount of exchanged is 200-250ml/kg over 10-14 day. • The removed plasma is replaced with albumin.

26. IVIG • Replaced PE in many centers as the treatment choice for AIDP because it is more widely available and easer to use than PE. • Dose of IVIG is 2 gr/kg infused over 2-5 days. • Treatment should begin preferably within first 7-10 day of symptoms. • Improvement often not immediate .mean time to improvement ranged from 6-27 day. • Unlike CIDP, corticosteroid do not appear beneficial in the treatment of AIDP; in fact ,some patient have done worse.

27. AIDP in children • The clinical , lab and EDX findings similar to adult • 75% have an antecedent infection • Major presenting complaint is pain • Most children with AIDP have a satisfactory recovery , even those with significant reduction in CMAP Ampl.

28. Acute motor-sensory axonal neuropathy (AMSAN) • Clinically and at least by initial EDX ,patient with AMSAN are indistinguishable from AIDP. • Patient with AMSAN develop rapidly progressive and severe generalized weakness over only a few day as opposed to a couple of wk in most patient with AIDP.

29. Ophtalmoplegia and difficulty in swallowing may be noted. • Muscle of facial expression are profoundly weak. • Most patient require ventilator support. • Sensation to all modality is reduced. • Complete areflexia is usually evident. • Prognosis of AMSAN much poorer than AIDP ;most patient have a slow or incomplete recovery. • Some authorities suggest that C.j infection and GM1 Ab are more commonly associated with axonal form of GBS.

30. Histologic evaluation performed early in the course of disorder is the only way to differentiate axonal GBS from psudoaxonal GBS. • Markedly diminish Ampl or absent CMAP within 7- 10 day of onset. • SNAP Ampl are profoundly reduced or absent. • Markedly abnormal reduction in recruitment . • Abundant fib and psw detected in most muscle especially distal limb.

31. Acute motor axonal neuropathy (AMAN)(chinese paralytic syndrome) • In northern china, AMAN is the most common variant of GBS. • Serologic evidence of recent C.j infection detected in 67- 92% of patient. • As in AMSAN , there is an abrupt onset of generalized weakness.the distal muscle often are affected more severly than proximal limb muscle. • Sensory sign and symptom are absent. • DTR may be normal or absent. • Patient generally make a good recovery within one years, but residual distal limb weakness is common. Mortality rate is less than 5%

32. The absence of prominent CSF pleocytosis help distinguish AMAN from poliomyelitis, which it can mimic. • The fact that many patient with AMAN recover quickly suggests that low Ampl or unobtainable distal CMAP are due not necessarily to axonal degeneration but to distal conduction block .

33. Characteristic NCS feature in AMAN is low Ampl or unobtainable CMAP with normal SNAP. • When CMAP are obtained, DML and NCVare normal. • F-wave usually unobtainable but,when present, show normal latency.

34. Other variant of GBS • Miller – fisher syndrome • Idiopathic cranial polyneuropathy • Pharyngeal-cervical-bracial weakness • Para paretic weakness

35. Miller – fisher syndrome • M/F=2/1 , mean age of onset in the early 40s. • An antecedent infection in 2/3 of cases. • Diplopia is the most common initial complaint. • Whether the ataxia is secondary to sensory dysfunction or a cerebellar lesion is controversial. In our experience , most patient have sensory ataxia. • Ptosis usually accompanies the ophtalmoparesis ,but pupillary involvement is uncommon.

36. Nearly 50% of patient describe paresthesia in face and distal limbs. • Areflexia is evident in over 82% • anti GQ1b demonstrate in most patient. • Most prominent EDX abnormality in MFS is reduced SNAP Ampl. • CMAP in the arm and legs are usually normal but, mild to moderate reduction in facial CMAP demonstrate in over 50% of patient. • Blink reflex may be abnormal. • There is generally no abnormal spontaneous activity in limb or paraspinal muscles but , fib may be detected in facial muscle.

37. Chronic inflammatory demyelinatingpolyneuropathy(CIDP) • An immune-mediated neuropathy characterized by a relapsing or progressive course. • Relapsing form=recurrent polyneuritis • Progressive form=progressive hypertrophic neuritis or chronic GBS • Sign and symptom of neuropathy must be progressive for at least 2 month, which distinguishes CIDP from GBS or AIDP.

38. Four typical clinical course of progression • Chronic monophasic(15%) • Chronic relapsing(fluctuation of weakness or improvement over week or months)34% • Stepwise progression 34% • Steady progression15% • Pattern of disease progression in CIDP analogous to MS. • CIDP most commonly present in adult with a peak incidence at about 40-60 years; slightly increased prevalence in men. • Relapsing form has an earlier age of onset ,usually in twenties • Relapses have associated with pregnancy

39. Most patient present with relapsing or progressive symmetric proximal and distal weakness of the arms and legs. • Early in the course of illness ,only distal weakness may be observed. however . If weakness remain distal , other diagnoses need to considered : hereditary demyelinating neuropathy ,Para protein related neuropathy, distal acquired demyelinating neuropathy.

40. Although most patient (80%)have both motor and sensory involvement , a few patient may have pure motor (10%) or pure sensory(5-10%)sign and symptom. • Sensory abnormality in 68-84%of patient , primarily affecting large fiber modality (vibration ,touch) • Sensory ataxia, positive Romberg sign ,wide base gait may be found.

41. Chronic sensory demyelinating neuropathy: only sensory sign and symptom. however EDX reveal motor nerve abnormality. • Most patient with a demyelinating neuropathy who have mainly sensory sign and symptom with normal or only mild distal weakness have an IgM monoclonal gammopathy . • Whenever a pure sensory neuropathy is present , consideration should be given to other diseases well, such as sjogren syndrome or paraneoplastic neuronopathy, both associated with sensory ganglionitis.

42. Most patient have areflexia or hyporeflexia. • Some patient develop dropped head syndrom secondary to neck extensor weakness. • Autonomic dysfunction (incontinency , impotency) less common. • Respiratory insufficiency reported in 8-15 % of patient. • 3-5% of patient have evidence of CNS demyelination clinically . • Patient may developed a myelopathy due to compression of spinal cord by hypertrophied nerve roots.

43. CIDP like neuropathy : • HIV infection • Hepatitis • Inflammatory bowel disease • DM • SLE • Monoclonal gamopathy of uncertain significance (MGUS) • Lymphoma • Bone marrow and solid organ transplantation • Paraneuoplastic complication of pancreas and colon carcinoma, SCC lung , melanoma, cholangiocarsinoma • Toxic induced neuropathy (procainamide, cyclosporine and tacrolimus)

44. LAB feature • An elevated CSF protein is found in 80-95% of patient. • Cell count is usually normal . • WBC CSF should be <10/mm3 • Elevated CSF cell count should lead to consideration of HIV infection, lyme, leukemic infiltration of nerve root • Oligoclonal band demonstrated in the CSF in 65% • MRI with gad may reveal hypertrophy and enhancement of the nerve root and peripheral nerve.

45. M-NCV • CMAP parameter most useful diagnostic test in demyelinating process. • a 50% drop in Ampl or negative peak area for define conduction block. • Increased CMAP Ampl , Increased NCV, decreased conduction block, seen in association with improvement in strength. • Clinical improvement primarily result of resolving conduction block.

46. S-NCV • >80% low Ampl or unobtainable SNAP. • A characteristic finding is abnormal median or ulnar SNAP when the sural SNAP are normal. • A similar discrepancy between the upper and lower limb SNAP seen in sensory ganglinopathy , but the EDX abnormality in such cases are axonal , not demyelinating.

47. EMG • Widespread fib and PSW are commonly detected in intrinsic foot and hand muscle and more proximal muscle. • The degree of fib and PSW is high during an exacerbation with a reduction during clinical remission.

48. treatment • Treatment of choice depend on other medical problem(avoid IVIG in renal defficiency) and accessibility. • Corticosteroid: prednisone 1/5mg/kg per day for 2- 4wk,then switch to alternate-day. • Functional muscle recovery is first noted in the proximal limb muscle.

49. PE: unfortunately response to PE is transient, usually lasting only a few wk. • PE used usually in combination with prednisone, in patient with severe generalized weakness. • PE used alone in patient in whom we wish to avoid long term prednisone(poorly controled DM or HIV infection) or in whom IVIG is contraindicated (renal insufficiency). • Used a trial course of PE in patient who do not fulfill all of criteria for CIDP or those that have an underlying condition making the diagnosis difficult(DM and superimposed CIDP- like neuropathy).

50. IVIG: for many authorities , IVIG has become the treatment of choice in CIDP. • A IgA level should be assayed before administering IVIG.patient who are IgA deficiency due to IgE anti IgA antibody or a congenital deficiency may develop anaphylactic reaction to IVIG.