HYDRORHACHIS CONGENITA- SPINA BIFIDA. 301 



When the spina bifida results from hydrorhachis externa, the wa J of 

 the sac consists of the arachnoid and dura mater ; the latter is occa- 

 sionally thinned or perforated, and then the wall consists of the arach 

 noid alone. If, on the other hand, the spina bifida result from hydro- 

 rhachis interna, the pia mater also assists in the formation of the wall. 

 The contents of the sac are pure serum, of the same constitution as 

 the cerebro-spinal fluid. When the spina bifida has resulted from hy- 

 drorhachis interna, the spinal medulla is either altogether absent, 01 

 is undeveloped. On the other hand, if it be due to hydrorhachis ex- 

 terna, the medulla may be perfectly normal ; but occasionally, even in 

 such cases, it is defective (Forster). 



The pathogeny and etiology of hydrorhachis congenita are obscure. 

 The collection of water is probably the primary disease, the incom- 

 plete formation of the spinal canal the secondary. 



The symptoms of hydrorhachis, complicated with partial spina 

 bifida of which alone we shall speak, as, in all cases combined with 

 great defect of the spinal medulla and extensive opening of the canal, 

 the children die before birth, or very soon after consist chiefly of the 

 objective signs due to the above-described tumor. There is usually 

 distinct fluctuation in it. At its base the edges of the bone may be 

 felt. It increases on expiration, still more on crying and straining, 

 and diminishes on inspiration. Occasionally it may be replaced, but 

 attacks of loss of consciousness and general convulsions are readily in- 

 duced by these attempts. In some cases the innervation of the lowe r 

 extremities, bladder, and rectum, is normal ; in others, especially where 

 the lower part of the medulla is defective, or has disappeared, the 

 lower extremities, bladder, and rectum, are paralyzed. The tumor usu- 

 ally increases rapidly in size and tension soon after birth. If the skin 

 reddens, becomes thin, and finally perforated, death, preceded by con- 

 vulsions and subsequent sopor, generally quickly follows the perfora- 

 tion. But, even where perforation does not take place, most of the 

 children die early of general marasmus, and it is very exceptional for 

 patients with spina bifida to attain or pass the age of puberty. 



Operative procedures are to be abstained from when complete pa- 

 ralysis and decided emaciation of the lower extremities indicate that 

 the spinal medulla is incompletely developed. In other cases we may 

 attempt careful compression, and, where this fails, proceed to the opera- 

 tions described for spina bifida in the text-books on surgery. 



