Basically, tissue changes may be considered in the following general divisions: (1) inflammatory, (2) degenerative, (3) neoplastic, (4) regenerative, (5) hyperplastic or hypertrophic, (6) those which begin as an inflammatory process and develop or remain as a degenerative process and (7) those which begin as a degenerative process with resulting secondary or symptomatic inflammatory changes. The character of the basic changes in the tissues serves as an index of the underlying pathologic process and thus may give a clue to the etiology.
No one today doubts the type of changes present in many of the common neurologic conditions. No one will deny that poliomyelitis and epidemic encephalitis are inflammatory diseases, even though degeneration takes place in the final stages. There can also be no question as to the type of changes in cerebral softening due to vascular occlusion, even though in the study of the end-result one may find perivascular
WINKELMAN NW, DAVISON C. SUBACUTE COMBINED DEGENERATION OF THE SPINAL CORDA STUDY OF THE UNDERLYING PATHOLOGIC PROCESS. Arch NeurPsych. 1933;29(2):317-331. doi:10.1001/archneurpsyc.1933.02240080107009