Size of mamillary bodies in health and disease: useful measurements in neuroradiological diagnosis of Wernicke's encephalopathy.

BACKGROUND

As the resolution of noninvasive neuroimaging techniques improves, small structures such as the mamillary bodies can be visualized and measured. The mamillary bodies are pathologically small in a number of neurological disorders, the most common and important is chronic Wernicke's encephalopathy (WE), or the Wernicke-Korsakoff syndrome (WKS), as it is often called. This disorder is caused by vitamin B1 deficiency (thiamin) and is seen most commonly in people who drink excessive amounts of alcohol. The disorder is easily preventable by using oral or parenteral thiamin. The aim of this study was to establish a range for the volume of the mamillary bodies in normal and in various disease states, particularly WE.

METHODS

Brains were taken from 2212 sequential autopsies performed at the New South Wales Institute of Forensic Medicine from 1996 through 1997. After fixation in 10% formalin, the brains were sectioned coronally and a block containing the mamillary bodies was dissected. The maximum vertical and transverse diameters of the mamillary bodies were measured using Mitutoyo vernier callipers and the volume calculated (V = 4/3 (a2b), where a and b are the vertical and transverse radii, respectively).

RESULTS

There were 164 cases with significant pathological changes in the mamillary bodies. These included cases with WE (25), Alzheimer's discase (10), infarction (11), and trauma (55). All but two of the WE cases were chronic or acute on chronic. The mean volume of the mamillary bodies was reduced by 60% in cases with chronic WE and by 25% in cases with Alzheimer's disease. In normal cases, there was a significant age-related reduction in volume, and males had larger mamillary bodies than females. Cases with alcoholic cirrhosis of the liver had normal mamillary body volumes.

CONCLUSIONS

There is a gross shrinkage of the mamillary bodies in cases of chronic WE, but clinicians need to consider other diagnoses, such as Alzheimer's disease, which can also result in shrinkage. These quantitative data will be helpful in the neuroradiological diagnosis of some of these disorders, particularly WE.