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Journal of Neurology, Neurosurgery, and Psychiatry, 1972, 35, 435-450

Arthrogryposis multiplex congenitaPart 2: Muscle pathology and pathogenesis

DARAB K. DASTUR, ZOHRA A. RAZZAK, AND E. P. BHARUCHA

From the Neuropathology Unit, J.J. Group of Hospitals, andthe Children's Orthopaedic Hospital, Bombay, India

SUMMARY Pathological findings are reported on 34 specimens from 16 cases of arthrogryposismultiplex congenita (AMC), including initial observations on paraffin sections from 28 muscles, andsubsequent observations on six additional specimens from three of these cases studied both histo-logically and histochemically. Thirteen of the 34 specimens (from 11 cases) were histologicallynormal, probably on account of an unaffected muscle being sampled. The most constant patho-logical feature in the remaining specimens was a disorganization of the muscle fibres and fascicles bysevere fibrosis; only three specimens (from two cases) did not show this. Very thin faintly striatedmuscle fibres embedded in this matrix were encountered in 10 specimens from nine cases. Anattempt at grouping of these atrophic or ill-developed fibres was noticed in four specimens; but thismay not be denervation atrophy. Two specimens (from two cases) showed 'myopathic' features.Repeat biopsy after two to three years was carried out on two affected muscles each from threepatients. Case 3 showed well preserved but uniformly small fibres. Case 4 showed extremely few andscattered small rounded fibres. Case 14 showed pronounced variation of fibre size in both, with bothatrophic and hypertrophied fibres. Normal nerves and spindles were seen in all these six specimensirrespective of the state of the muscle, and excessive fibro-fatty tissue in cases 4 and 14. Histo-chemical examination for oxidative enzymes, ATPase, and phosphorylase in these six specimensrevealed a normal checkerboard pattern and ratio of type I and type IL fibres, in case 3 only. Themuscles of case 4 showed a preponderance of type I fibres. One specimen from case 14, showed thesame fibres reacting for both oxidative enzymes and phosphorylase, suggesting a lack of developmentof fibres. The intrafusal fibres were mainly of type I in all. Two possible pathogenetic mechanismsoperating in early embryonic life, which may lead to the characteristic changes of AMC, are dis-cussed: (1) a defect in the development of the muscle whereby the full recruitment of myoblasts fromthe mesenchyme of the limb-bud does not take place and muscles do not form adequately; (2) a lackof innervation of the muscles on account of arrested growth of anterior horn cells. The combinedoperation of both these mechanisms is also considered. Fibrous tissue replaces the muscle tissuethat is lacking, and contractures and deformities ensue. The evidence gathered on our material, suchas the very thin smooth muscle fibres, the large numbers of well-formed nerves and spindles especiallyin the repeat biopsies, and the above-mentioned histochemical feature, would appear to favour thehypothesis of ill-developed muscles in the production of AMC in the majority; in the rest denerva-tion playing either a major or concurrent role.

A brief review of the literature implicating the observed excessive amounts of fat and connec-joints and the central nervous system in the tive tissue in muscle biopsies and thereforeproduction of arthrogryposis multiplex con- emphasized the myopathic nature of the con-genita (AMC), has already been presented dition, which he called 'myodystrophia foetalis(Bharucha et al., 1972). Changes in the muscle deformans'. Rossi (1947) recognizing the con-have also been held responsible for the deformi- dition to be a clinical syndrome with joint andties. muscle involvement called it 'arthro-myodys-

In 1908, Howard described the condition as plastic syndrome'. Banker, Victor, and Adams'dystrophia muscularis congenita', emphasizing (1957) reported two cases of 'arthrogryposisthe muscular part of the defect. Middleton (1934) multiplex due to congenital muscular dystrophy',

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Darab K. Dastur, Zohra A. Razzak, and E. P. Bharucha

where the deformities were considered secondaryto the muscle changes, which were 'identical tothose seen in progressive muscular dystrophy'.Subsequently Pearson and Fowler (1963) re-viewed eight cases (two of their own in sibs) ofmuscular dystrophy with probable arthrogrypo-sis.

Sheldon (1932) had introduced the concept ofmuscular maldevelopment, through the nomen-clature 'amyoplasia congenita'. He postulatedan aplasia, hypoplasia, or dysplasia of certainmuscle groups leading to an imbalance at joints.Hillman and Johnson (1952) also suggestedmuscular aplasia as the primary lesion inarthrogryposis multiplex congenita. Kite (1955)had further incriminated a failure of embryonicmyoblasts as the first cause of all the changes.Frischknecht, Bianchi, and Pilleri (1960) re-ported cerebral defects, degeneration of pyra-midal tracts and anterior horn cells, and pseudo-myopathic changes in muscles in a family witharthrogryposis which he described under theall-inclusive title of 'neuro-arthro-myo-dysplasiacongenita'. Swinyard and Mayer (1963) reviewed70 cases and felt that the primary pathologicalchange may be in the spinal cord, in the musclesthemselves, or in the connective tissue. Theyexpressed uncertainty about AMC being eithera 'single disease entity' or a 'manifestation ofseveral different aetiologies'.To the best of our knowledge, there is only

one recent histochemical study of the musclesin AMC. Fenichel (1969) in a study of cerebralinfluence on muscle fibre typing includes sevencases with 'arthrogryposis', according to thedefinition of this condition given by Drachmanand Coulombre (1962) that it is 'a non-specificsign of foetal immobilization'. Fenichel con-siders 'arthrogryposis' to be a 'model of skeletalfixation during muscle maturation due toabnormal suprasegmental function'.The main objectives of this study have been

described by Bharucha, Pandya, and Dastur(1972). In the present paper the histologicalchanges observed in the muscles will be describedand our current views on the pathogenesis ofAMC will be presented.

METHODS

Initially 28 muscle biopsy specimens were availablefrom 14 cases (two specimens each were availablefrom 10 cases and three from two). Paraffin sectionsstained by haematoxylin and eosin (H and E), thepicro-Mallory method for connective tissue, and by

phosphotungstic acid haematoxylin (PTAH) wereexamined in each case. Muscle fibre diameters weremeasured in most by micrometry.

Later, from three of the children who could berecalled, two further muscle biopsy specimens fromeach could be obtained. Fresh frozen sections ofthese were processed for the following histochemicalreactions: succinic dehydrogenase (SDH) andreduced nicotinamide adenine dinucleotide (NADH),for oxidative enzyme activity; myofibrillar adenosinetriphosphatase (ATPase); and phosphorylase forglycolytic enzyme activity. Fibre diameters weremeasured and ratios of type I to type II fibres wereobtained. In addition, fixed frozen and paraffinsections were stained with H and E, picro-Mallory,and PTAH stains. Thus in all 34 muscle biopsieswere studied.Serum creatine phosphokinase (CPK) was esti-

mated in four cases by the method of Hughes (1962).

RESULTS

FIRST EXAMINATION The histopathological ob-servations in all cases biopsied are summarizedin Table 1. The largest pathological group of

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FIG. 1. (NP/E/830b). Very thin muscle fibresembedded in fibrous tissue; two normal sized fibres atthe upper end. H and E, x 265.

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FIG. 2. (NP/E/613a). (a) Ill-defined group of very thinimuscle fibres contrasting withgroup of well-formed fibres,both in fibrous matrix. Noteessentially normal musclespindle in the latter. H anid E,x 105. (b) Same muscle showinigcross-striations on very thinfibres of slightly varying sizePTAH, x 660.

muscle comprising 10 specimens from ninecases, showed a similar type of change, ofgreater or lesser severity in different cases. Thisconsisted essentially of a dense fibrosis withtotal lack of organization of muscle intofascicles together with the presence of very finemuscle fibres embedded in this fibrous tissue.Thus Fig. 1 shows very fine strands of musclefibres in a collagenous matrix, contrastingstrikingly with two much larger normal fibres. Inanother area of the same muscle, fibres of a

slightly larger dimension, of varying sizes butstill small, are seen. This was from the quadri-ceps muscle of a 2 year old girl, with an averagefibre diameter of 9-7 . only and a range of5-17 ,u. In this case the biopsy of anothermuscle, the deltoid, showed even less muscletissue in the form of thin straggly fibres.

A clearer contrast between the better preservedand the thin fibres which are now attempting agrouping is seen in Fig. 2a from the deltoidmuscle of an infant aged 15 months; a normalmuscle spindle was also encountered. Even thevery small fibres which average 9 4 ,u in size, incontrast to the normal fibres of 38-1 u, showedclear cross-striations with PTAH staining (Fig.2b). In five muscle specimens from five casesPTAH stain revealed cross-striations even inthin fibres in which H and E failed to reveal thesame. A picture more clearly indicative of groupatrophy (Fig. 3a) is seen at times, as in thespecimen of biceps muscle of a 4 year old boy.Closer examination of such fibres, in H and Estained sections, generally showed them to besmooth and with crowding of nuclei on thefibres (Fig. 3b). Essentially normal muscle

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FIG. 3. (NP/E/775b). (a) Twowell-defined groups of thinmuscle fibres in fibro-fattytissue; note muscle spindle withprominent connective tissue andintrafusal fibres. (b) Closer view

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FIG. 4. (NP/E/390, 2). Solitary small group of verytiny muscle fibres in a section otherwise totally devoidof muscle tissue. H and E, x 660.

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FIG. 7. (NP/G/39a). Right biceps brachii muscle. (a) Small fascicles made up of uniformly atrophied fibres.H and E, x 105. (b) Normal checkerboard pattern of type I and type II extrafusal fibres. Intense activity ofintrafusal fibres in tandem spindles. NADH2, x 105. (c) Intrafusal fibres showing varying grades of activity;nerves not showing activity. Normal checkerboardpattern ofextrafusalfibres. Phosphorylase, x 265. (d) Intenseactivity in the two nerve twigs, probably in the Schwann sheath. ATPase, x 265.

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FIG. 8. (NP/G/27a). Right deltoid muscle. (a) Clustered nuclei in two large groups suggesting fascicularoutline. (b) Closer view ofsome of the clusters showing stray small muscle fibres in them. Both frozen sections,H and E, x 105 and x 265 respectively. (c) Strongly type I intrafusal fibres and one or two small extrafusalfibres; nerve approaching spindle and within it is segmentally stained. SDH, x 265. (d) Strongly positive type IIfibres, extrafusal and intrafusal in one spindle, the other larger spindle showing type I fibres, which were un-stained but brought to view by reducing the illumination. Phosphorylase, x 265.

spindles are seen in such cases without atrophyof the intrafusal fibres-for example, Figs2a and 3a-with occasionally slight prominenceof intrafusal connective tissue (Fig. 3a).At times, the fibrosis or the lack of differentia-

tion into muscle tissue were so pronounced thatonly the presence of a muscle spindle indicatedthat the biopsy was in fact from a muscle. Atother times, search through an entire sectionwould reveal only an extremely small group ofmuscle fibres in a specimen otherwise made upof fibrous tissue only, as in Fig. 4 from aquadriceps muscle of an 8 month old girl. Herethe fibre diameter could not be measured.

Only one of these 34 specimens of muscle,including those belonging to this group of 10,showed a similar fibrosing and disorganizing

change in an intramuscular nerve (Fig. 5).Sheath cell proliferation accompanied themyelin loss in this nerve twig. In this specimenof a hamstring muscle from an 11 year old girl,no muscle tissue was to be seen at all. Anothermuscle of this case was normal.

In all, 13 of the initial 28 biopsied muscleswere histologically normal. These were generallyclinically less affected or unaffected musclesbiopsied for contrast with the more affectedmuscle. In case 9, however, all three biopsyspecimens were normal on account of theirbeing restricted to the site of surgical exposurewhich was the region of the congenitallydislocated hip joint.

In none of the four cases so tested was thereany elevation of the serum creatine phospho-

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kinase (CPK) level, including the two caseswhere clinical, electromyographic, and histo-logical evidence was in favour of a myopathicchange. Thus in case 8 there was a mildlydystrophic change in the form of variation ofmuscle fibre size (range 6-61 ,>) though withoutan increase in connective tissue. The othermuscle in this case did not show even thischange. The other myopathic patient in ourseries (case 1) showed a more characteristicchange of variation in size and rounding offibres together with increase of fibrous and fattytissue and some accumulations of small mono-nuclear cells (Figs 6a, b). The less affected child(case 8) had an older sib similarly affected. Theother child (case 1) showed the more floridmyopathic change in the gastrocnemius muscle,which, however, was not enlarged. This childalso had the 'policeman-tip' position of theextremities, characteristic of AMC.

In two of the specimens there was no muscletissue at all and it was difficult to say whetherthis was consequent to the arthrogrypoticchanges or mainly the result of an inadequatebiopsy. Both these cases however showed histo-logical evidence in their other muscle biopsy offibrosed nerves (case 5) and ill-developedfibrosed muscle (case 16) respectively.

SUBSEQUENT EXAMINATION From three of thepatients (nos. 3, 4, 14) who could be recalled fora second examination two to three years afterthe first, two muscle biopsies each could beobtained.

In one of them (case 3) with more flexioncontracture at elbows than at knees, whereoriginally a normal quadriceps muscle had beensampled, weak muscles of the arm and theforearm were now biopsied. The biceps brachiiand an extensor muscle from a forearm bothshowed generalized smallness of fibre-size(Table 2), without group atrophy. H and Estained frozen sections showed this clearly (Fig.7a). Histochemical preparations confirmed thisfinding in addition to revealing a normalcheckerboard pattern of type I and type ILfibres. Both the oxidative enzymes, SDH andNADH, demonstrated this (Fig. 7b), as also theintense positivity of intrafusal fibres. Theroughly equal proportion of type I and type ILfibres in both muscles (Table 2) was observedwith both oxidative enzymes and phosphorylase(Fig. 7c). The latter also demonstrates that

occasional spindles contained type II intrafusalfibres. While nerves were faintly stained withthose enzymes (Fig. 7b, c, where nerves are seenoutside the spindle), they showed a moreintense activity for ATPase (Fig. 7d) where theSchwann cell outline is revealed, possibly by themitochondrial ATPase (Padykula and Herman,1955). The spindle capsule and nuclei have alsotaken up the stain.

Case 4 who had originally presented with aclearly neuropathic picture on EMG and changesof dubious nature in one deltoid muscle atfollow-up showed severe disorganization andlack of muscle tissue in both deltoid and bicepsmuscles of the other limb. There were only raresmall fibres encountered in a fibro-fatty matrix.An interesting feature was the presence ofclusters of nuclei arranged in a peculiar fashion,as though representing the totally atrophiedfibres within a fascicle. This feature is clearlyseen in Figs 8a, b, where two such clusters showtwo or three fibres remaining. Both the deltoidand biceps muscles were similar to each other,the latter showing even fewer fibres and nonuclear clusters. There was a preponderance oftype I fibres in all the enzyme preparations(Table 2).Over large areas there was no recognizable

muscle tissue, but only muscle spindles. Whileall spindles in preparations for oxidative enzymeactivity contained type I intrafusal fibres only(Fig. 8c), the spindles encountered in thepreparations processed for phosphorylase acti-vity showed type I and/or type II intrafusalfibres-for example, Fig. 8d. The nerve fibresoutside and within the spindles showed onlyslight positive activity (Fig. 8c).One of the muscles (biceps brachii) from the

third patient with neurogenic atrophy (case 14)diagnosed on original EMG examination,showed severe disorganization very similar tothat in case 4, except that there were compara-tively more fibres with obvious variation offibre size (Table 2). In one field, type I fibres 20,37, 78, 104, and 148 ,u in diameter were en-countered (Figs 9a, b). In muscle specimens ofadult control subjects we have noted the meanfibre diameter of type I fibres to be 78 + 17 ,u;truly atrophic fibres were considered to be thoseless than 44 ,u or two standard deviations (SDs)below the mean and truly hypertrophic fibres tobe more than 114 V., two SDs above the mean(Razzak, 1970). Considering that we are dealinghere with a child aged about 5 years there is

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Arthlrogryposis multiplex congenita

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FIG. 9. (NP/G/28a). Right biceps muscle. (a) Scattered type I fibres of varying size in a loose fibrous matrix.(b) Closer view ofsome of the fibres, which were actually measured, including one hypertrophiedfibre (see text).(Both SDH, x 105 and x 265 respectively.) (c) Two type II and one intermediate type scatteredfibres, one of theformer showing vacuolation. Phosphorylase, x 660. (d) Faintly defined nerve fibres in five bundles of a largeintramuscular nerve. SDH, x 105. (e) Same nerve showing stronger activity in axon and weaker in fibre sheaths.NADH2, x 660.

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FIG. 10. (NP/G/28b). Quadriceps muscle. (a) Vaguely defined group of muscle fibres of varying size anduniform activity in fibro-fatty matrix. (b) Another group showing four medium-sized and onie excessively hyper-trophied fibre (see text). Both SDH, x 40 and x 265 respectively.

true atrophy as well as true hypertrophy of hermuscle fibres.

Rarely, there were small fibres with vacuoles,appearing as degenerating muscle fibres, as seenin the type II fibres in the phosphorylasepreparation shown in Fig. 9c. The largest fibreseen in this Figure is possibly of intermediatetype. The phosphorylase reaction, like theATPase, appeared to reveal a small but everpresent proportion of fibres of a type inter-mediate between types I and II. This wasnoticed in all the six muscle specimens of thesethree patients (Table 2).A large nerve made up of five bundles,

included in the same biceps muscle, showedfeeble activity of the nerve fibres in SDHpreparations (Fig. 9d), but clearer presence ofoxidative enzymes within the fibres in NADHpreparations (Fig. 9e).The quadriceps muscle from the same patient

showed a few relatively well-preserved fascicles,and a few ill-defined groups of small fibres(Fig. 10a) in a fibro-fatty matrix. There was anapparent preponderance of type I fibres as seenin both SDH and NADH preparations, with aratio of type I:type IL of 4:1 (Table 2). Thefeature of note was the presence in phosphorylasepreparations of a large number of dark staining-that is, apparently type II fibres so that theratio here of type I: intermediate: type II fibreswas 1 1: 1: 3a 1 (Table 2). This feature was seen inrespect of large, small, and normal-sized fibres.It indicated that the same fibres manifestedactivity of both oxidative and glycolytic enzymes,

and not that there was a true preponderance ofeither of the two main types of fibres. Fibre sizevariation with a range of 26 to 98 ,u was againobserved (Table 2). One unusually large type Ifibre (diameter of 170 V) is illustrated in Fig. 10b,which also shows a group of relatively smalltype I fibres of 50-60 V. (compare with Fig. 9b).A rather vague group atrophy was observed atone or two spots. These features contrasted withthe extremely thin 'ill-developed' fibres of theother quadriceps muscle of this patient biopsiedearlier (Fig. 1, Table 1).

COMMENT

On the basis of the initial histological examina-tion alone, the most impressive change in themuscle biopsy specimens was the presence innearly two-thirds of our cases with AMC ofextremely thin muscle fibres embedded irregu-larly in fibrous tissue which formed the greaterpart of the specimen. This was irrespective ofthe age of the patient. While the smallness offibre size was suggestive of denervation, theabsence of grouping, except in three of the 10muscles (cases 6, 10, 12) and the presence ofconnective tissue actually among the fibres,were features against a denervation atrophy.The fibres appeared smooth and faint and cross-striations were apparent only with PTAHstaining. The overall impression created wasthat of ill-formed muscle fibres.The mechanism of this lack of development is

not clear, but failure or retardation in develop-

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ment of musculature in utero is one possibilityand lack of neurogenic stimulus or trophicimpulse is another. The former appears aplausible mechanism, since it is known thatnerves are not concerned with organizingprimary muscle formation (Hamilton, Boyd, andMossman, 1962). There is at least evidence inexperimental animals that muscles will developin limbs devoid of innervation (Hamburger,1939).

It is relevant at this juncture to recapitulate afew salient facts regarding the development ofmusculature in the human foetus. Theseobservations have been drawn mainly fromHamilton et al. (1962). In general, it appearsthat the limb muscles of most tetrapods are notderived from the myotomes but from the limbbuds. With the exception of nerve fibres,Schwann cells, melanoblasts, and possibly theendothelium of blood vessels and lymphatics,all the subepidermal cellular elements of thelimb including those of its muscles are nowconsidered to take their origin in situ from themesenchyme of the embryonic buds. Theintrinsic muscles of the limbs also differentiatein situ.

Branches of the nerves supplying the segmentscorresponding to those of the limb-bud reachits base. As the bud elongates to form a limb,they extend into it. The muscles split into aventral or limb-flexor group and a dorsal orlimb-extensor group. The nerves of a limb arelikewise divided into anterior or posteriordivisions supplying flexor and extensor musclesrespectively. Thus the muscles in the adult limbhave a fairly consistent segmental innervation.As development of myoblasts proceeds, they

become elongated and increase in girth, so thatin the human embryo of only 5-8 mm CR-lengthmyofibrillae can be identified. From beinguninucleate, the myoblasts become multi-nucleate and, when they are about 1 t indiameter, cross-striations appear. They assumea tubular structure and the myotubes are con-verted into muscle fibres. In the last trimester ofgestation the central nuclei migrate to themargin of the fibres which increase in girth bymultiplication of their myofibrillae.

Striated muscles are said to grow fromrecruitment of new myoblasts from the adjacentmesenchyma, by divisions of early myoblastsbefore fibrils have formed and by the increase insize of the individual fibres. Postnatal growthseems to be entirely due to enlargement of pre-

existing muscle fibres. The tendons of musclesseem to develop independently of the musculartissue, and are secondarily linked to it by theconnective tissue of the perimysium. Hence, asHamilton et al. (1962) conclude, the contractileand the connective tissue elements in a muscleconstitute a composite organ rather than a singleuniform tissue.

Extrapolating these embryological observa-tions to our histological findings on muscles inAMC, it seems likely that in this condition thedevelopment of the limb-buds and even ofindividual muscle fibres may be adequate, butthe total number of fibres developed and presentat birth may be grossly inadequate. In otherwords, the recruitment of the myoblasts fromthe adjacent mesenchyme appears defective. Thenet result may be a lack of differentiation of themesenchymal mass into individually recognizablemuscles. The mesenchyme seems to have differen-tiated preferentially and excessively towards theformation of collagenous fibrous tissue. Since nonew muscle fibres can be expected to developafter birth (vide supra), whatever postnatalgrowth of muscles occurs in patients with AMCwould probably be the result of hypertrophy ofthe pre-existing fibres. Where the process is notvery severe and at least a fair complement ofmuscle fibres is present, a reasonable develop-ment of muscle bulk may be expected and per-haps boosted by the stimulus of physiotherapyand exercises (see discussion by Bharucha et al.(1972)).Our surgical colleague at the Children's

Orthopaedic Hospital in Bombay, who carriesout successive operations to correct the jointdeformities in such children, occasionally reportsthe development of grossly detectable muscleplanes where at earlier operations no muscletissue could be visualized at all and the deepfascia and 'muscles' may even have looked likeone fibrous mass (Mullaferoze, 1970).While nerve supply is not imperative to the

initial development of muscle, innervationnevertheless seems essential for the furthergrowth of muscle fibres. In the pig, for instance,while the muscle differentiates before nerve con-nections are established, the latter are necessaryfor full maturation, as shown originally byBardeen (1900). In the muscle of the humanfoetus nerve fibres are recognizable at about 10weeks' gestation and terminal sprouts makecontact with muscle fibres by the 11th week, asdemonstrated by Tello (1922) and Cuajunco

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(1942). However, it is not until between the 14thand 24th weeks that the motor endplates startdeveloping and they probably reach their fullmaturity a little later than that. This would meanthat adequate muscle fibre growth from the 4thto the 6th month can take place only under thestimulus of nerve supply.During early embryogenesis, till about the

20th week in the human foetus, there is no clearhistochemical differentiation of muscle fibresinto different types (Dubowitz, 1966). Anessentially uniform pattern with type II fibrespredominating develops by the 30th week(Fenichel, 1966). During the last few weeks ofgestation, there is a shift towards the normalcheckerboard pattern of type I and type IIfibres (Dubowitz, 1968).

Hence, in AMC, a possible mechanism wouldbe normal initial development of muscle fibresfrom myoblasts, but arrest or retardation oftheir further development from about the 11thweek onwards on account of lack of neuralstimulus. This could result from failure ofdevelopment or early degeneration of anteriorhorn cells in the spinal cord, as in fact has beenobserved in a certain proportion of cases by anumber of workers (reviewed by Bharucha et al.,1972).

It is equally conceivable that due to a dis-order early in embryonic life both the myoblastand the neuroblast are retarded in their furtherdifferentiation into the muscle fibre and theanterior horn cell respectively. It may be recalledthat the maturation of the anterior horn cellsfrom the neuroblasts of the basal lamina of theprimitive spinal cord takes place during aboutthe second month of intrauterine life or beforethe embryo reaches the 30 mm stage (Hamiltonet al., 1962). Hence in some cases of AMCprimary muscle fibre development may suffermore, while in others impairment in furthergrowth of muscle fibre under a neural stimulusmay be the predominant defect.The evidence from the repeat biopsy speci-

mens from three of the cases, collected mainlyfor histochemical examination, was difficult toevaluate definitively on account of the presenceof very few fibres in three of the six specimensobtained. However, four interesting pointsemerged. In case 3, where initially a normalmuscle had been sampled, clinically weakmuscles from arm and forearm (Table 2)showed a histochemically normal checkerboardpattern and normal ratio of fibre size throughout

both specimens, suggesting disuse atrophy,probably resulting from limitation of movementat the joints concerned. Identical disuse atrophywas observed by us with immobilized limbs(Patel, Razzak, and Dastur, 1969).

In case 4, while the very few generally smalland scattered fibres did not permit any histo-logical diagnosis, the groups of clustered nucleiin H and E stained frozen sections, with a straymuscle fibre in two or three groups, perhapsindicated a loss of preformed fibres. The totalnumber of fibres in both specimens was too fewto stress the relative preponderance of type Ifibres, but a depletion of type II fibres wouldpoint to denervation (Engel and Brooke, 1965).In four of Fenichel's (1969) cases of 'arthro-gryposis' with brain malformation, there was awider spectrum of fibre size with largest fibres oftype II, but both fibre types in equal proportions.The rounding of fibres observed was takenmerely as a feature of the lack of support ofthese scattered fibres which were generallyfloating about in the fibro-fatty tissue as happensin muscular dystrophy, but this rounding alonewas not taken to be evidence for dystrophy inthis case.The two muscles of case 14 were different

from one another, but while the more affectedspecimen of M. biceps brachii contained rela-tively few fibres, they both shared the commonfeature of a few huge hypertrophied fibres(Table 2). This was in line with our earlierexpectations. Equally interesting was the pres-ence in the same fibres, in the less affectedquadriceps muscle, of activity for both oxidativeenzymes and phosphorylase. This appearedpossible if the muscle fibres were still in anundeveloped state. However, this muscle con-trasted with the opposite quadriceps biopsied21 years earlier, in that excessively thin ill-developed fibres were not seen any more andindicated that the muscle had in fact 'grown' ina small but appreciable manner.The presence of large numbers of well-formed

muscle spindles and nerves in all the six repeatbiopsy specimens, reflected at least the integrityof peripheral nerves and indirectly suggestedthat at least a proportion of the spinal motor-neurones had developed and made contact withthe appropriate muscles.

Either on the basis of dysplastic muscle fibresor of ill-formed anterior horn cells, proliferationof fibrous tissue in the muscle may be expected.Deformities of the limbs and contractures at the

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Arthrogryposis multiplex congeniita

joints, which constitute the hallmark of theclinical picture of AMC, could naturally beexpected to result from excessive fibrosis ofgroups of muscles and due to inadequacy ofmuscle tissue available to produce movementsat the joints. According to Badgley (1943), if thelimb-bud rotation occurring normally in thethird foetal month fails due to embryonic arrestof muscle development, then the joints do notdevelop and articular surfaces do not form. Hepostulates this mechanism for the production ofcongenital dysplasias of the hip.

Another feature to be expected with either ofthe alternative pathogenetic mechanisms wouldbe a lack of progression of the disease afterbirth, since there is no evidence, in our materialor of others, of either clinical, electromyo-graphic, or pathological progression. Moreover,electrical evidence of regeneration was generallylacking, as was the case with all of our patientswho showed denervation potentials (Bharuchaet al., 1972). It is also significant that two of our10 cases with atrophic looking fibres revealed anormal pattern on EMG. Thus there is nosimilarity here with either the infantile or thejuvenile types of spinal muscular atrophy.

One also wonders if there is a truly dystrophicform of AMC. The two original cases of Bankeret al. (1957) and some of those of Pearson andFowler (1963) show how congenital musculardystrophy may occasionally be accompanied byfibrotic contractures similar to those of AMC.Such observations prove some of the jointdeformities to be non-specific, but do notnecessarily establish a myopathic form of AMC.This disease is probably not the commondenominator of a variety of pathogenetic pro-cesses, but the result of one or two only-namely, an embryonal lack of development ofspinal motor neurones and/or deficient histo-genesis of muscle per se. The two cases in ourown series which we have tentatively classifiedas 'myopathic' did not satisfy all the histo-logical criteria of a muscular dystrophy and didnot show an elevation of serum CPK.

Thus the overall impression on histologicaland histochemical examination, including thefollow-up study, was that lack of development ofmuscle was responsible for AMC in the majorityof our cases. In a small proportion (about athird) denervation atrophy could have been themain or an additional factor.

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Bardeen, C. R. (1900). The development of the musculatureof the body wall in the pig, including its histogenesis andits relations to the myotomes and to the skeletal andnervous apparatus. Johns Hopkins Hospital Report, 9,367-400.

Bharucha, E. P., Pandya, S. S., and Dastur, D. K. (1972).Arthrogryposis multiplex congenita: I: Clinical andelectromyographic aspects. Jolurnal of Neurology, Neutro-surgery, and Psychiatry, 35, 425-434.

Cuajunco, F. (1942). Development of the human motor endplate. Contributions to Embryology, 30, 127-152.

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Engel, W. K., and Brooke, M. H. (1966). Muscle biopsy as aclinical diagnostic aid. In Nelurological Diagnostic Tech-niquies, pp. 90-146. Edited by W. S. Fields. Thomas:Springfield, 111.

Fenichel, G. M. (1966). A histochemical study of developinghuman skeletal muscle. Neurology (Minneap.), 16, 741-745.

Fenichel, G. M. (1969). Cerebral influence on muscle fibretyping. The effect of fetal immobilization. Archives ofNeltrology, 20, 644-649.

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Hamburger, V. (1939). The development and innervation oftransplanted limb primordia of chick embryos. Journal ofExperimental Zoology, 80, 347-389.

Hamilton, W. J., Boyd, J. D., and Mossman, H. W. (1962).Hutman Embryology. 3rd edition. Heffer: Cambridge.

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the histochemical method for adenosine triphosphatase.Jouirnal of Histochemistry and Cytochemistry, 3, 170-195.

Patel, A. N., Razzak, Z. A., and Dastur, D. K. (1969).Disuse atrophy of human skeletal muscles. Archives ofNeutrology, 20, 413-421.

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Pearson, C. M., and Fowler, W. G., Jr. (1963). Hereditarynon-progressive muscular dystrophy inducing arthro-gryposis syndromes. Brain, 86, 75-88.

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Rossi, E. (1947). Le syndrome arthromyodysplasiquecongenital. Helvetica Paediatrica Acta, 2, 82-97.

Sheldon, W. (1932). Amyoplasia congenita. Multiplecongenital articular rigidity: arthrogryposis multiplex

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Tello, J. F. (1922). Die Entstehung der motorischen undsensiblen Nervenendigungen. 1. In dem lokomotorischenSystem der hoheren Wirbeltiere. Muskuldre Histogenese.Zeitschrift far Anatomie und Entwicklungsgeschichte, 64,384-440.

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