Incidental findings on brain magnetic resonance imaging: systematic review and meta-analysis
BMJ 2009; 339 doi: https://doi.org/10.1136/bmj.b3016 (Published 17 August 2009) Cite this as: BMJ 2009;339:b3016All rapid responses
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In their assessment of incidental findings on brain MRI scans Morris
et al fail to mention the pituitary gland 1. Pituitary adenomas are not
uncommon. A post-mortem study looking at the presence of pituitary
adenomas in asymptomatic individuals found a prevalence of 10% 2. Of those
with a pituitary tumour, 5% had multiple tumours within the gland,
representing an estimated prevalence of 0.5% within the general
population. Most of the adenomas are lactotrophic or non-functional 3.
Previous work looking at MRI scans of the general adult population have
showed a prevalence of asymptomatic pituitary macro-adenomas of up to 0.3%
4-8. However, the protocols used for doing an MRI of the brain are not
designed for looking at the pituitary gland, thus it is very possible that
several microadenomas would have been missed in these large series.
Reference List
1. Morris Z, Whiteley WN, Longstreth WTJ, Weber F, Lee YC, sushima Y
et al. Incidental findings on brain magnetic resonance imaging: systematic
review and meta-analysis. BMJ 2009;339:547-50.
2. Buurman H, Saeger W. Subclinical adenomas in postmortem
pituitaries: classification and correlations to clinical data.
Eur.J.Endocrinol. 2006;154:753-8.
3. Tomita T, Gates E. Pituitary adenomas and granular cell tumors.
Incidence, cell type, and location of tumor in 100 pituitary glands at
autopsy. Am.J.Clin.Pathol. 1999;111:817-25.
4. Yue NC, Longstreth WT, Elster AD, Jungreis CA, O'Leary DH,
Poirier VC. Clinically serious abnormalities found incidentally at MR
imaging of the brain: data from the Cardiovascular Health Study. Radiology
1997;202:41-6.
5. Tsushima Y, Taketomi-Takahashi A, Endo K. Prevalence of abnormal
findings on brain magnetic resonance (MR) examinations in adult
participants of brain docking. BMC Neurology 2006;5.
6. Weber F, Knopf H. Incidental findings in magnetic resonance
imaging of the brains of healthy young men. Journal of Neurological
Sciences 2006;240:81-4.
7. Katzman GL, Dagher AP, Patronas NJ. Incidental findings on brain
magnetic resonance imaging from 1000 asymptomatic volunteers. JAMA
1999;282:36-9.
8. Vernooij MW, Ikram MA, Tanghe HL, Vincent AJP, Hofman A, Krestin
GP et al. Incidental findings on brain MRI in the general population.
N.Eng.J.Med. 2007;357:1821-8.
Competing interests:
None declared
Competing interests: No competing interests
Although the paper dealt with incidental findings, the authors noted,
"Reassuringly, the age related trends in silent brain infarcts and white
matter hyperintensities that we observed were consistent with existing
population based studies, etc." But there was no discussion about why age
related changes occurred.
Because MRI identifies regions with higher than usual water content
as areas of brightness, it is very likely that such changes in the elderly
reflect the effects of increased blood viscosity on intra-capillary
pressure, as increased blood viscosity is a part of the aging process.
In 1934, Landis reported that the extent to which water passed out
through the capillary wall was determined by the intra-capillary pressure,
and the higher the pressure the greater the level of transudation. In
accordance with the Poiseuille formula, intracapillary pressure would be
determined by viscosity but mainly by the capllary radius.
This means that in the chance event of a cluster of smaller than usual
capllaries, the increased pressure needed to sustain flow of viscous blood
would increase the amount of water passing out into the tissues. That
water would be identified by MRI as an area of brightness. But any event
(such as an emotional upset) or of some factor (such as smoking) which
increased blood viscosity, could be expected to involve larger capillaries
and thus increase the frequency of areas of brightness. This is the
likely mechanism of the MRI hyperintensities seen in the elderly.
The occurrence of such changes in the elderly draw attention to the
need to reduce blood viscosity, and several approaches have been shown to
be effective. The lowering of the level of fibrinogen could be the most
effective move. If the haematocrit is raised then it should be
normalised. In the long term, 6 grams daily of fish oil, which increases
the fluidity of the red cell membrane, should be considered. It seems
inappropriate to recognise age-related changes and not treat them.
Competing interests:
None declared
Competing interests: No competing interests
This article is very interesting. This review showed that the silent
brain infarction and white matter abnormality is the most common finding
among non neoplastic incidental findings. The prevalence was increase
according with the age. The advance of highly sensitive techniques for
brain imaging such as MRI can detect potentially abnormal findings. Such
findings include lesions with an appearance typical of infarction; when
these appear in persons without a history compatible with stroke. This
lesion was called "silent infarcts." The strong relationship of these
findings with age and other stroke risk factors suggests that they may
themselves be risk factors or even manifestations of clinically important
cerebrovascular disease. Many prior studies have focused on the rate of
silent infarcts in various disease states. Acute ischemic stroke patients
have been found to have unrelated, silent infarcts in 11% to 29%.Silent
brain infarction is also an important risk factors for further stroke and
dementia. Previous study showed that global cognitive function was
significantly worse in participants with silent brain infarcts on the base
-line MRI than in those without such infarcts. Appropriate control of
vascular risk factors should be performed.
Competing interests:
None declared
Competing interests: No competing interests
Re: Incidental findings on brain MRI should include the pituitary gland
See figure 1 - the prevalence of pituitary adenomas is quantified in
this meta-analysis!
Competing interests:
None declared
Competing interests: No competing interests