946 PARALYSIS OF THE OBTURATOR NERVE. 



to callus formation, the obturator nerve may be implicated or undergo 

 compression. Paralysis of this nerve may also be caused by pressure 

 of the foetus in difficult parturition. 



Symptoms. At rest the limb may appear normal, but in move- 

 ment it is strongly abducted, the foot carried outwards, or dragged 

 along the ground. In some cases the pastern is flexed, and backing 

 is very difficult. These symptoms are accompanied, or soon followed, 

 by marked atrophy of the muscles inside the thigh. Diagnosis is 

 assisted by rectal or vaginal exploration. 



One recorded case was in a five-year-old mare, which became 

 lame without visible cause. In walking, and still more so in trotting, 

 the right hind foot was strongly abducted. The hip- joint was 

 markedly flexed, and the stifle drawn upwards and outwards, as in 

 string-halt. When backing there was difficulty in moving the right 

 foot, but weight was placed on the limb as usual. Recovery occurred 

 in between four and five months, during which .strychnine was 

 administered. The case described by Nocard (see section on 

 " Fracture of the Pelvis ") as due to compression of the nerve trunk 

 by the callus, resulting from a fracture through the obturator foramen, 

 was no doubt one of obturator paralysis. There was atrophy of the 

 adductor group of muscles, and a peculiar lameness. 



W. Willis has described two cases of obturator paralysis, and 

 referred to others as having been seen. In each instance there 

 existed a swelling, which later developed into a callus over the pubis 

 at the point where the obturator nerve crosses that bone. In mares 

 it could be detected by examination through the vagina. Willis 

 at first diagnosed these cases as "fractured pelvis," as indeed they 

 were. The average duration of the cases appears to have been about 

 three months, and the paralysis appeared to march concurrently 

 with the development of the callus, marked abduction of the limb, 

 its principal symptom, appearing as the soft callus increased in size 

 and diminishing as the callus became smaller and more fully ossified. 

 In one instance, though the animal was able to work, a certain degree 

 of abduction continued for a year. 



The prognosis must vary with the cause. It is favourable in cases 

 arising from difficult parturition, but very unfavourable in those 

 due to fracture, or tumour formation, because surgical interference is 

 impracticable. Treatment is largely expectant, especially in cases 

 unassociated with gross lesions. Rest, followed after an interval by 

 gradually increasing exercise, and massage of the adductor muscles, 

 may prove beneficial. 



