Clinical And Electrophysiological Study In Patients With ALS And Motor Axonal Neuropathy

Part 1 Clinical and Electrophysiological study of neuromuscular junction in ALS patientsBackground and ObjectiveAmyotrophic lateral sclerosis(ALS)is a neurodegenerative disorder which characterized by the progressive loss of motor neurons(MN)in the brain and spinal cord.The mechanism of motor neuron death in ALS is still unclear.Oxidative stress and mitochondrial dysfunction play an important role in the pathogenesis of ALS.Previous studies showed that the neuromuscular junction(NMJ)contained abundant mitochondria and was intolerant to oxidative stress,and the NMJ had primary dysfunction in ALS animal model.On the one hand,NMJ dysfunction leads to the dysfuction in the production and transportation of some skeletal muscle derived neurotrophic factors,on the other hand,the oxidative stress products produced by NMJ might be transported to MN in spinal cord through reverse axoplasmic transport.The dysfunction of NMJ might cause or aggravate the apoptosis of MN in spinal cord,which played an important role in the pathogenesis of ALS,that is,the dying back theory.Repetitive nerve stimulation(RNS)was a commonly used electrophysiological method to evaluate the function of NMJ in patients.Previous studies had shown decrement in low-frequency RNS(LF-RNS)in ALS patients.However,due to different frequencies,different measurement methods and different positive standards,the results of decrement degree,decrement distribution and decrement mode were inconsistent in different studies,and whether the decrement was related to clinical progress was also inconsistent.There were few studies on the specificity of the decrement in ALS patients compared with other lower motor neuron syndrome(LMNS).Hand muscle atrophy is an important clinical manifestation,which often appears in a unique pattern called split hand syndrome.Split hand syndrome manifests that hand muscle wasting preferentially affects the 'thenar hand',with relative sparing of the hypothenar muscles although they are innervated by the same spinal segments(C8 and T1).The phenomenon is seen in more than half of ALS patients,and the mechanism is not completely known.The use frequency of thenar muscle was higher,and it was easy to produce more oxidative stress in human.NMJ is a more sensitive part of oxidative stress,which is also an important pathogenic factor of ALS.Whether the NMJ dysfunction of different muscles in hand is different,and whether it is related to the phenomenon of split hand is lack of research.The purpose of this study is to evaluate the characteristics of NMJ dysfuction and its relationship with clinical manifestations in ALS patients with different stimulation frequencies(2Hz and 3Hz);to analyze the value of LF-RNS in the differential diagnosis of ALS and LMNS;to analyze whether there were differences in NMJ dysfuction of skeletal muscles in different hands and the relationship between NMJ dysfunction and split hand phenomenon;Methods1.Patients1.1 ALS patientsPatients with ALS who met the inclusion criteria at Department of Neurology,were retrospectively reviewed from July 2016 to September 2019.Inclusion criteria were as follows:(1)definite,probable,clinically probable laboratory-supported ALS according to the revisited El-Escorial diagnostic criteria;(2)patients who underwent routine electromyography examnation and RNS;(3)lower motor neuron syndrome(LMNS)caused by other reasons was excluded.1.2 Myasthenia gravis(MG)and Lambert-Eaton myasthenia syndrome(LEMS)patientsIn order to compare the decrement mode,51 MG patients and 23 LEMS patients diagnosed at the same time were included.The diagnosis of MG was confirmed by serological antibody and positive neostigmine test with fluctuant diplopia.LEMS patients were confirmed by increment more than 100%in high frequency RNS or facilitation test.1.3 LMNS patientsIn order to analyze the role of RNS in differentiating ALS from other LMNS,25 patients with LMNS syndrome diagnosed at the same time were selected.The criteria for inclusion were:(1)clinical and electrophysiological manifestations conforming to LMNS;(2)the diagnosis was unequivocal;(3)underwent routine EMG and RNS in our hospital.2.Clinical dataClinical data of ALS patients included onset age,disease course(the time interval from onset of clinical symptoms to electrophysiological examination).The revised ALS functional rating scale-Revised(ALSFRS-R)used to assess patients with ALS.For assessment of muscle strength in intrinsic hand muscles,we used the motion angle of fingers instead of the manual muscle testing grading scale.3.Neurophysiological examinations3.1 The electrodiagnostic studies were performed on a Keypoint4 electromyography system.Negative amplitude of compound muscle action potential(CMAP)in abductor pollicis brevis(APB),abductor digiti minim(ADM)and first dorsal interosseous(FDI)of ALS patients were recorded.The split hand was defined as split ratio<0.6.Split ratio=Amplitude of CMAPAPB/Amplitude of CMAPADM3.2 RNS with 7 stimuluses of 2HZ and 3 HZ was performed on TRA,APB,ADM and FDI muscles.For each train of repetitive stimuli,decrement of the amplitudes from the first to 4th,5th,7th CMAPs were recorded as D1,D2,D3 respectively and was expressed as a percentage.Decrement was definite abnormal when D1/D2/D3?10%,while decrement was borderline abnormal when D1/D2/D3>8%,Maximum decrement was recorded as Dmax.In order to analyze the degree of recovery after decrement,the parameter was introduced,?D=D3-D2.In order to analyze the relationship between NMJ dysfuction and split hand syndrome,the parameter decrement difference(DD)was introduced.DD=D2APB-D2ADM.In 80 ALS patients,decrement data was collected from 67 APB muscles,71 ADM muscles,37 FDI muscles and 37 TRA muscles.59 patients underwent the LF-RNS test of APB and ADM in the same hand,of which 37 patients underwent the LF-RNS test in FDI at the same time,whose RNS data of these patients were also used to analyze the relationship of split hand syndrome and NMJ dysfuction.Decrement data of MG patients was collected from 42 ADM muscles,32 APB muscles and 51 trapezius muscles.Decrement data of LEMS patients was collected from 10 ADM muscles,21 APB and 5 TRA muscles.Decrement data of LMNS patients was collected from 25 ADM muscles,24 APB and 25 TRA muscles.Results1.75%ALS patients had decrement in LF-RNS in at least one of these muscles(TRA,APB,FDI,ADM).2.Positive decrement in hand muscle was related to the onset site,and the proportion of upper limb onset was higher.3.Under 2HZ or 3HZ stimulation,the positive rate and decrement degree of TRA were the highest,followed by APB.4.The positive rate and decrement degree of each skeletal muscle under the stimulation of 3HZ were slightly higher than that of 2HZ,but there was no statistical significance.5.The Dmax of the APB,FDI and TRA were negatively correlated with their amplitude of CMAPs respectively.The decrement degree of APB and FDI is negatively correlated with their moving angle,and the decrement degree of each skeletal muscle was not related with onset age,disease course and ALSFRS-R.6.There are three decrement modes for ALS patients,mode 1:U-shaped or L-shaped decrement;mode 2:setback in recovery;mode 3:progressive decline.The proportions of three modes were 55.7%,25.80%and 18.5%respectively.The proportion of mode 2 and mode 3 in ALS patients was higher than that in MG patients.In ALS patients,the level of ?D in 3Hz stimulation was lower than that in MG patients.7.Decrement in APB was superior to TRA and ADM in distinguishing ALS and other LMNS.When Dmax of APB is more than 6.20%,the sensitivity and specificity of diagnosing ALS were 86.67%and 72.00%,respectively.8.The DD of the patients with split hands was significantly higher than that of the patients without split hands.The partial correlation analysis showed that the DD was slightly negatively correlated with the split ratio(r=-0.3525,p=0.0081).Conclusion1.More than half of ALS patients have LF-RNS decrement in at least one skeletal muscle,in which the decrement ratio of proximal muscle is higher than that of distal muscles;APB involved most significantly when referred to distal limb muscles.2.Of these muscles with decrement in ALS patients,more than half presented as U-shaped decrement with a low degree of recovery;meanwhile,there was setback in recovery in decrement suggesting that both presynaptic and postsynaptic were involved in ALS patients.3.Decrement in skeletal muscle could be used to distinguish ALS from other LMNS,among which APB was more effectively compared with other muscles.4.The decrement of APB was more significant than ADM,and the decrement difference was related to split ratio,suggesting that NMJ dysfuction might be involved in the split hand syndrome.Part 2 Clinical and electrophysiological study of patients with motor axonal neuropathyBackground and ObjectiveLower motor neuron syndrome(LMNS)includes motor neuron disease involving the anterior horn cell or the motor axon and/or its surrounding myelinl.Patients with amyotrophic lateral sclerosis(ALS)present signs of upper motor neuron(UMN)involvement,which can be differentiated from pure LMNS.However,progressive muscular atrophy(PMA),a variant of ALS,manifested isolated LMNS due to the degeneration of lower motor neurons(LMNs).ALS is a neurodegenerative disease without an effective treatment to date.However,immune-mediated motor axonal neuropathy which exhibits similar clinical signs to LMN-onset ALS is treatable.However,axonal loss results in similar changes on nerve conduction studies(NCS)and needle electromyography(EMG),regardless of whether the lesion is at the level of motor neuron,root,plexus,or peripheral nerve.Chronic motor axonal neuropathy(CMAN)although rarely reported which manifesting limb weakness and muscle atrophy clinically and motor axonal neuropathy electrophysiologically was difficult to distinguish from LMN-onset ALS.Nevertheless,the motor axonal neuropathies secondary to ALS(ALS-MAN)have a unique distribution of nerve involvement,which is characterized by split hand and split leg.The current study is to summarize the clinical and electrophysiological characteristics of patients with CMAN,and identify how they are different from those associated with AMAN and ALS-MAN.Methods1.Participants1.1 CMAN patientsThis study first describes patients diagnosed as CMAN in the Department of Neurology,from April 2016 to September 2018,and summarizes their clinical and electrophysiological manifestations.Inclusion criteria:(1)progressive weakness and muscle atrophy,disease course>2 months,physical examination conforming to LMNS;(2)The blood ganglioside antibody test was positive;(3)Immunotherapy is effective or improved after follow-up;(4)Excluding LMNS caused by other reasons.1.2 AMAN patientsClinical and electrophysiological data of 20 AMAN patients at Department of Neurology,Qilu Hospital of Shandong University from April 2016 to September 2018 were retrospectively reviewed to form a comparison group to CMAN.In addition to fulfilling the diagnostic criteria of AMAN,patients met the following three conditions:(1)there was spontaneous potential with or without large motor unit potential(MUP)suggesting axonal degeneration on needle EMG;(2)there was no conduction block(CB);(3)results of anti-ganglioside antibody were positive.1.3 ALS-MAN patientsPatients with ALS-MAN at Department of Neurology,from April 2016 to September 2018 formed another comparison group to CMAN group.Inclusion criteria of ALS-MAN were as follows:(1)definite and probable ALS according to the revisited El-Escoria criteria;(2)distal CMAP amplitude under 80%lower limit of normal range(LLN)in at least two motor nerves;(3)results of anti-ganglioside antibody were negative.1.4 Healthy controls(HCs)We recruited additionally 41 healthy subjects as HCs.All HCs provided written informed consent to take part in the study.There was no statistical difference in age,sexuality,height among CMAN group,AMAN group,ALS-MAN group and HCs.2.Neurophysiological studiesNCS were performed using surface stimulation and recording techniques.The electrodiagnostic studies were performed on a Keypoint4 EMG system.The parameters of motor nerves consisted of negative amplitude of CMAPs,distal motor latency(DML),motor conductive velocity(MCV)in median nerve,ulnar nerve,deep peroneal nerve and tibial nerve recorded by abductor pollicisbrevis(APB),adductor digiti minimi(ADM),extensor digitorum brevis(EDB)and abductor hallucis(AH),respectively.Standard value of amplitude was introduced to compare the decline degree of different nerves.Standard value of CMAP amplitude=CMAP amplitude/LLNs of each nerve.In order to compare the distribution of different nerve involvement in the same limb,split ratio was introduced.split ratio of upper limb(SRU)=Amplitude of CMAPAPB/Amplitude of CMAPADM,and split ratio of upper limb(SRL)=Amplitude of CMAPEDB/Amplitude of CMAPAH.Results1.CMAN patients showed symmetrical progressive weakness,with distal limb prodominant.4 patients had deceased tendon reflex,1 patient had active tendon reflex.IgG anti-GM1 antibodies were positive in all patients,immunotherapy was effective,and the prognosis was well.In 5 patients with CMAN,the amplitude of CMAPEDB remained within the normal range,while that of CMAPAPB,CMAPADM and CMAPAH was decreased in all patients.There was no significant difference in SRU of CMAN patients and HCs,while SRL was significantly higher in the CMAN group.The standard value of CMAPEDB was higher than that of CMAPAh statistically.2.The CMAP amplitudes decreased in different degrees in patients with AMAN.The amplitudes of CMAPEDB remained normal in 11 patients,while the amplitudes of CMAPAPB,CMAPADM and CMAPASH remained normal in only 1,2 and 2 patients respectively(p<0.0001).The standard value of CMAPEDB was significantly higher than that of other nerves,and there was no significant difference in standard CMAP amplitude of other nerves.Compared with HCs,the SRL was higher than that of HCs group,despite comparable SRU.In addition to the different disease course,the MRC score of CMAN patients was higher than that of AMAN patients.In terms of the distribution of nerve involvement,the SRL of CMAN patients was higher than that of AMAN patients,and there was no statistical difference in other electrophysiological parameters.3.SRU and SRL in ALS-MAN group were significantly lower than those in HCS group.Amplitudes of CMAPEDB,SRU,and SRL in CMAN/AMAN group were higher than those in ALS-MAN group,while amplitudes of CMAPADM and CMAPAH were significantly lower than those in ALS-MAN group.When SRL>0.59,the sensitivity and specificity to diagnosis CMAN/AMAN were 84%and 91.89%,respectively.Conclusion1.In the LMNS spectrum,CMAN was characterized by weakness of the distal limbs with chronic onset,decreased tendon reflexes(occasionally active tendon reflexes),rare cranial nerve involvement,and good response to immunotherapy.2.The clinical manifestation of CMAN was similar to those of AMAN except disease course and severity of weakness.CMAN and AMAN had similar nerve involvement pattern manifesting reverse split leg phenomenon3.Nerve involvement in ALS-MAN was charactered by split hand and split leg phenomenon,which was different from CMAN.SRL could be used as a reliable index to distinguish CMAN/AMAN and ALS-MAN.