JohnSusac, 50 Second Street, SE, Winter Haven, FL 33880jsusac@neurohaven.com
R. Bakshi, A.D. Gean, F.R. Murtagh, R.B. Daroff
Submitted February 05, 2004
We thank Dr. Lim et al for their interest in our paper, and
congratulate them for making the correct diagnosis of Susac's syndrome,
which is frequently missed at major academic medical centers in the United
States.
We have seen positive diffusion-weighted MRI images (DWI's) in
Susac's
syndrome, but do not feel that they reliably differentiate the syndrome
from
demyelinating diseases, which may also show hyperintensity on DWI. [5]
Ideally, the information derived from DWI should be correlated with
apparent
diffusion coefficient (ADC) maps to differentiate a true restricted
diffusion abnormality from T2 shine-through. Bright lesions on DWI that
are
associated with decreased ADC probably only indicate that the lesions, of
whatever etiology, are "active". Numerous disease processes besides
ischemia may demonstrate restricted diffusion on DWI scans (infection,
neoplasm, trauma, demyelination, etc.). Even the presence of true
restricted diffusion does not differentiate among various causes of
ischemia, such as vasculitis, thrombosis, and emboli. Moreover, the
restricted diffusion abnormality in ischemia is a transient finding, often
lasting for about four weeks, and might readily be missed at various
stages
of Susac's syndrome.
References
5. Zivadinov R, Bakshi R. Role of MRI in multiple sclerosis I:
inflammation and lesions. Frontiers in Bioscience 2004;9:665-683.
We thank Dr. Lim et al for their interest in our paper, and congratulate them for making the correct diagnosis of Susac's syndrome, which is frequently missed at major academic medical centers in the United States.
We have seen positive diffusion-weighted MRI images (DWI's) in Susac's syndrome, but do not feel that they reliably differentiate the syndrome from demyelinating diseases, which may also show hyperintensity on DWI. [5] Ideally, the information derived from DWI should be correlated with apparent diffusion coefficient (ADC) maps to differentiate a true restricted diffusion abnormality from T2 shine-through. Bright lesions on DWI that are associated with decreased ADC probably only indicate that the lesions, of whatever etiology, are "active". Numerous disease processes besides ischemia may demonstrate restricted diffusion on DWI scans (infection, neoplasm, trauma, demyelination, etc.). Even the presence of true restricted diffusion does not differentiate among various causes of ischemia, such as vasculitis, thrombosis, and emboli. Moreover, the restricted diffusion abnormality in ischemia is a transient finding, often lasting for about four weeks, and might readily be missed at various stages of Susac's syndrome.
References
5. Zivadinov R, Bakshi R. Role of MRI in multiple sclerosis I: inflammation and lesions. Frontiers in Bioscience 2004;9:665-683.