Structural brain abnormalities such as ventricular enlargement are rob
ust correlates of schizophrenia, but the degree of difference compared
with unrelated normal controls is only moderate (< 1 standard deviati
on), and only 40% of patients have values on these measures that fall
outside of the normal distribution, Family studies can help to clarify
the meaning of this overlap by controlling for some of the non-schizo
phrenia-related gelzetic variation in neuroanatomical traits, Computer
ized tomographic scans of the brain were used to measure ventricular-a
nd sulcal cerebrospinal fluid (CSF) to brain ratios (VER and SBR) for
each hemisphere in 16 pairs of discordant siblings from the Copenhagen
Schizophrenia High-Risk Project, Schizophrenics' values for VER and S
BR exceeded those of their nonschizophrenic siblings in 75% of the pai
rs; on average, patients' values on these measures were I and 5 standa
rd deviations larger, respectively, than those of their nonschizophren
ic siblings, Sulcal and left hemisphere effects,cere significantly mor
e pronounced than ventricular and right hemisphere effects. After cont
rolling for between-family variation structural brain abnormalities ap
pear to be more prevalent and more pronounced in schizophrenia than ha
s previously been assumed with relatively greater deviation observed f
or cortical and left hemisphere measures of CSF space enlargement. (C)
1997 Society of Biological Psychiatry.