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1 Electromomyography diagnosis of Morton syndrome Study ENMG (89 cases) Medical and Surgical Treatments Jean-Pierre CASANOVA MARSEILLE

2 1) HISTORIC In 1845, Lewis Durlacher (Queen's Surgeon of England) iden?fied this pathology. In 1876, TG. Morton (of Philadelphia) gives his name for this pathology described 30 years ago, so what could have been called "Durlacher's syndrome" (let's pay homage to him) is now called Morton's Syndrome. More recently, in 1973, G. de Bisschop published for the first?me, with P. Broudeur, the study of the sensory nerve conduc?on in the interdigital plantar nerve of the foot Morton syndrome. Bisschop (de) G, Broudeur P, Fresco R, Giudicelli S, Mouren P. Electromyographic correla?ons of Thomas Morton disease and scia?c radiculopathy. News from Medicine and Surgery of the Foot 1973: 8: In the opinion of the authors, this is a delicate technique reserved to experienced specialists. 2

3 2) GENERALITY The syndrome of Morton, Morton neuroma, intermetatarsal neuroma or interdigital neuroma is a pathology of rela?ve frequency in the case of electromyography studies (4 suspicions out of thousand examina?ons). The most common presents complaints include: cramps, burning pain int he forefoot and intermizent electrics discharges, dysesthesias to the toes (2nd, 3rd inter-digital spaces) At last,there is this imperious need, almost pathognomonic, to take off his shoes a_er a walk to bring a rapid relief of the symptoms. This is the compression of the metatarsals heads and the transverse intermetatarsal ligament which trigger the nervous stress and irrita?on 3

4 Morton's neuroma is a benign lesion of fibrous nature, perineuronal fibrosis and demyelinisa?on of interdigital nerves The female to male ra?o for Morton s neuroma is (68% / 32%). There is no set age and from our study the mean age is 56 years (28-73). Certain sports ac?vity can increase risk of developing pathology such a prolonged walk, runnig, imposes to stop any furth training 4

5 3) Treatments of first inten?on Orthopedic insole Cor?costeroids Injec?ons Stop training In the great majority of cases, these measures do not provide a complete resolu?on of symptoms Surgical indica?on in the absence of improvement may be cura?ve 5

6 4) Anatomy and histology Interdigital nerves originate are composed from the lateral and medial plantar nerves. The nerve distribu?on is similar (to the innerva?on found at the level of) the hand. Indeed, the medial plantar nerve provide to 1st, 2nd, 3rd and half of the 4th toe, compared to the median nerve which provide to the fingers wich a similar topography. The lateral plantar nerve provide to the other half of the 4th toe and the totality of the 5th one (similarity to the ulnar nerve). The essen?al difference is compression site.

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9 Several factors are involved in the occurrence of the syndrome: The intersec?on formed by the medial and lateral plantar nerves is the object of intense pressures provoqued by the proximity of the ventral aspect of the toes flexor muscle. But this is the compression of the interdigital nerves by the metatarsal heads and by the transverse ligament which is the major cause of the neurinoma. 10

10 Histological studies of the excised mass reveal peri-neuronal fibroses, demyelina?ons and endoneuronal fibrosis with, in more advanced cases, axonal degenera?on with neovasculariza?on. The fact that the third space is most o_en concerned is explained by the fact that the intermetatarsal distance is less important than for the other spaces, which increases the risk of nerve compression.

11 5) Electromyographic diagnosis Besides the clinical exam, several exploratory examina?ons are most cited in the medical literature (ultrasounds, magne?c resonance, etc.). The study of plantar nerves CNV sensi?vy is more reliable by the use of bezer electrodes for orthodromic s?mulidetec?on, with, of course, a perfect methodology (anatomical map). The use of the specific s?mula?on electrode avoids the usual pikalls (bad posi?on, use of an?-anatomic s?mula?on electrodes such as annular electrodes, etc.).

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15 SEXE AGE LATENCE 1 LATENCE 2 LATENCE 3 LATENCE 4 AMPL 1 AMP 2 AMPL 3 AMPL 4 F , F , F , F , F ,7 0.1 O F , F , M , F , M , M , F , F , M , M , F , F , M 47 7,8 7,8 0 8,1 0,1 0,1 0 0,4 M 52 5, ,7 4,9 0,7 0,8 0,7 0,8 F 31 6,5 0 7,3 6,8 0,8 0 0,2 0,5 F 63 6,5 6,5 0 6,5 0,2 0,4 0 0,2 F 60 4,6 4,3 4,1 4,6 0,2 0,3 0,1 0,3 F 62 8,3 8,1 0 8,2 0,2 0,2 0 0,1 M 66 6,8 7,7 7,1 6,4 0,5 0,4 0,4 0,3 F 82 8,1 10 9,3 8,2 0,2 0,7 0,3 0,4 F ,7 4,9 0,8 0,7 0,5 0,7 F 62 8,1 8,5 0 8,3 0,2 0,5 0 0,7 F 46 6,1 6,8 6,8 5,9 2 0,5 1 0,7 F 46 5,5 6,3 6,5 6,2 1, ,6 M 46 6, ,7 0,4 0,4 0 0,4 M 68 6,6 6,7 6,4 6,4 0,2 0,1 0,3 0,3 F 66 10,6 10, ,4 0,2 0,3 0,3 0,3 M 82 6,6 7 6,7 8,1 0,2 0,2 0,2 0,2 M 82 6,6 7,1 6,5 6,1 0,2 0,2 0,2 0,2 F 64 6,4 7,9 7,5 6,4 0,2 0,2 0,2 0,2 M , ,5 0,3 0 0 F 73 5,9 5,8 0 5,6 0,2 0,2 0 0,2 F 72 6,5 6,5 0 5,9 0,2 0,3 0 0,4 F 42 5,2 5,4 5,6 6,2 1 1,7 1,6 0,5 F 54 5,4 6,9 6,3 5,3 0,5 0,7 0,7 0,8 F 54 7,1 7,1 0 4,9 0,2 0,3 0 0,7 M ,2 5,8 0, M 60 7,7 9,4 8 8,5 0,7 0,7 0,7 0,7 F 50 5,9 6,6 10,5 6,1 1 0,4 0 0,5 F 70 6,2 5,8 0 6,2 0,3 0,2 0 0,3 F 64 5,4 6,3 6 6,4 0,7 0,7 0,7 0,5 F 71 4,1 4,2 4,2 4,1 0,4 0,4 0,4 0,4 F 75 5,2 4,5 0 5,4 0,3 0,3 0 0,3 M 65 5, ,2 0, ,4 F 21 6,5 6,4 5,8 5,7 0,7 0,8 0,7 0,7 F 55 5,7 5,6 5,1 5,1 0,3 0,2 0,4 0,5 F 30 5,4 6,7 6,6 6,7 0,3 0,4 0,8 0,8 M 28 9,2 9,4 0 10,4 0,2 0,1 0,1 0,1

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19 The plots obtained are in the form of nega?ve deflec?ons to the number of 4 (the 4 interdigital spaces must be systema?cally explored as well as those on the opposite side). Latencies are preferably taken at nega?ve peaks, and latency differences or more frequently the absence of poten?als are interpreted as par?al conduc?on blocks. The difference between the amplitudes is also to be considered as in all cases of denerva?on (with reserva?on related to the condi?ons of the examina?on).

20 6) Comments Electroneuromyographic examina?on, if performed rigorously, is the only examina?on capable of establishing a func?onal and quan?ta?ve assessment of nerve compression in the context of a Morton syndrome. This is a par?cularly reliable and reproducible examina?on for (Compression more proximal) and thus to be able to orientate towards the other differen?al diagnoses: metatarsal synovi?s, stress fractures, bursi?s, tenosynovi?s of the tendons extensors.

21 1)Mean latencies at the first, second, third and fourth inter-digital spaces with standard devia?ons (in ms) are: : ,25 +/-1,05 6,91+/-1,31 6,56+/-1,10 31+/-1,13 Popula@on Morton-posi@f : 6,43 +/-1,35 6,84+/-1,04 8,13+/-1,26 6,32+/-1,17 2) Au niveau des Amplitudes (en µv) les résultats sont les suivants : Popula@on Morton-néga@f : 0,49+/-0,36 0,56+/-0,33 0,56+/-0,31 0,57+/-0,29 Popula@on Morton-posi@f : 0,45+/-0, 0,45+/-0,13 0,20+/-0,08 0,48+/-0,30

22 In Morton-posi?ve popula?on there are 10 cases out of 41 of localiza?ons Double (24%) and 2 out of 41 bilateral cases.

23 Other exams Echographie IRM

24 Surgical treatments Pathways: dorsal or ventral Techniques: simple release or resec?on Other technique: dorsal transposi?on of the interdigital nerve

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26 Conclusions The clinical diagnosis of Morton's syndrome is easy when it is sought but difficult to affirm on this single criterion. The electroneuromyographic func?onal examina?on is then of great interest between "expert" hands, it makes it possible to affirm the diagnosis and to reveal less common or mul?ple loca?ons and thus to make the surgical gesture more effec?ve.

27 With a well-performed electroneuromyographic diagnosis, and appropriate treatment, the athlete can resume training in about 90% of cases within four to six weeks following surgery.