Pathoaenesis. Anatomical Changes. Symptoms. 



681 



tliat are sometimes present. In one case the disease was com- 

 plicated with diffuse ossification of the vertebrae from the mid- 

 dle of the dorsal region to the sacrum, but there were no adhe- 

 sions between the bones and the dura mater (Hutyra & Marek). 



Pathogenesis. The hemorrhages and dilatation of the ves- 

 sels found by Kitt and Stoss, and 

 Cadeac, indicate that the disease is of 

 an inflammatory nature. The plates 

 of bone that are formed, press upon 

 the motor and sensory nerve roots in 

 their immediate neighborhood and, 

 owing to the increase in thickness of 

 the membranes, pressure may be ex- 

 erted upon the spinal cord itself. They 

 also hinder the free movements of the 

 cord in the vertebral canal during 

 changes of position of the body, and 

 consequently there is a chance that the 

 nerve roots', and even the spinal cord 

 may be torn in the early stages of the 

 disease. In time, the mechanical irri- 

 tation in the cord and nerve roots sets 

 up a chronic inflammation. 



Anatomical Changes. Scattered 

 along the dura mater from the cervi- 

 cal to the lumbar portions of the cord, 

 and often in other parts, there are 

 white or dark l)luish-red plates of bone 

 which by fusion may form quite large 

 bony patches. In very severe cases, 

 the dura may be converted into a hard 

 tube. The majority of the plates are 

 to be found on the ventral surface 

 where they are almost exclusively 

 situated in the early stages (fig. 96). 



Fig. 96. 



meningitis, (a) Inner surface 

 of the dvira mater in the lum- 

 bar and sacral portions of the 

 cord, (b) Sensory (c), motor 

 nerve roots, at places sur- 

 rounded by bony plates, (d) 

 Plates of" bone' in the dura 

 mater. 



The plates develop on the inner surface of the membrane and are covered on 

 the inner face with a thin layer of endothelium and on the outer with a thick con- 

 nective tissue layer. They are composed of genuine bone tissue and show no 

 tendency to unite with the vertebra?. There is an increase m the amount of con- 

 nective tissue in the nerve roots and degeneration of the nerve fibei-s, while the 

 lesions in the cord are less pronounced, but in severe cases are those of myelitis set 

 up by pressure. 



Symptoms. A variable length of time elapses before clin- 

 ically recognizable s^auptoms make their appearance. Accord- 

 ing to Cadeac, this may be as long as one to two years after 

 the onset of the disease. The first symptom observed is usu- 

 allv evidence of pain owing to the stretching of the sensory 



