Sieve State

SIEVE STATE, sieve-like condition (syn. siebformige Degeneration, Swiss cheese brain), a term introduced in 1848 by Durand-Fardel to denote that relatively rare change in brain tissue when, on cross-section, it resembles a sieve or strainer, i.e., appears as if permeated with numerous holes or cavities resembling Swiss cheese. The indicated cavities and openings represent greatly dilated perivascular lymph spaces of the brain. Under the microscope, in each cavity a blood vessel can be found, while the cavity wall reveals a picture of gliosis [see separate plates (pp. 671-672), Fig. 4]; some (Saltykov) found inside the cavities the development of a fibrous network and scarring of the cavities. In the origin of the sieve state, atrophy of the brain, decrease in its mass, and as it were, the withdrawal, retraction of brain tissue from the vessels were previously given primary importance; later it turned out (Borst) that apparently a significant role is played by stagnation of lymph in the perivascular spaces due to sclerotic changes in the pia and arachnoid membranes of the brain. The sieve state is most frequently encountered in senile atrophy of the brain and chronic meningitis; it is most sharply expressed in the area of the gray ganglia of the base of the brain (thalamus, corpus striatum).