Review: Differences in Hippocampal Metabolism Between Amnestic and Non-Amnestic MCI Subjects

The reviewed article is  ‘Differences in hippocampal metabolism between amnestic and non-amnestic MCI subjects: automated FDG-PET image analysis’ by Mariani and colleagues and freely available here at the time of writing. In the abstract, the researchers conclude that

Comparison between the two MCI subtypes showed MTL hypometabolism in aMCI subjects possibly reflecting the fact that most had prodromal AD

In the introduction, the researchers outline some of the previous evidence showing a deficit in glucose metabolism in the Medial Temporal Lobe and providing a context for the current study. The aim of the study is clearly described  in the abstract

The aim of this study was to assess whether 18F-fluorodeoxyglucose positron emission tomogrpaphy differentiates amnestic (aMCI) from single-non-amnestic mild cognitive impairment (snaMCI) with executive dysfunction


  • The study included 30 right-handed MCI subjects who had been referred to the University of Milan neurology department.
  • 85% were referred by the GP
  • 15% were self-referred. The self-referrals are interesting as this might be different from the usual referral routes in other healthcare systems.
  • The diagnostic criteria are clearly stipulated – 6/12 of subjective/objective evidence of cognitive impairment, normal ADL, MMSE >= 24, CDR of 0.5, performance of 1.5 SD below norms on >= 1 cognitive dimension on neuropsychological testing.
  • There was an extensive list of exclusion criteria and here I thought that the subjects might differ significantly from a routine clinical population with MCI e.g Hachinski ischemic score > 4, thyroid disorders, kidney or liver disorders, history of alcohol dependence as well as a number of other criteria.
  • Subjects underwent a battery of neuropsychological investigations.
  • Petersen’s criteria for amnestic MCI were used and those for single non-amnestic MCI are stipulated in the paper.
  • The protocol for PET imaging and analysis of the images was clearly described.
  • PET images were compared to a control group of previously acquired images on 7 subjects


  • The average age in both MCI groups was roughly 73 years (see paper for exact figures)
  • There were significant differences between the two MCI groups on a number of neuropsychological tests which might be expected. I wasn’t clear on whether there was an adjustment for multiple comparisons
  • 13 aMCI subjects went on to develop dementia
  • Compared to the controls both MCI groups showed hypometabolism in the posterior Cingulate gyrus
  • Compared to the single non-amnestic executive dysfunction MCI group the Amnestic MCI group had hypometabolism in the Medial Temporal Lobe
  • I couldn’t see the data on the control group (I might have just missed this)


The researchers draw some interesting conclusions. They caution on the small sample size while noting that the posterior cingulate gyrus hypometabolism might be a result of a disconnection from limbic areas since it is not usually affected by Alzheimer’s pathology in the early stages of the disease while also adding that a number of the subjects with aMCI went on to develop AD. They suggest that the executive dysfunction group exhibiting hypometabolism in the PCG might mean that this area is also disconnected with this pathology.

It will be interesting to see if these findings with the posterior cingulate gyrus are replicated with larger sample sizes as this might suggest a potentially important location for pathology in both executive and amnestic MCI as well as associated pathologies such as Alzheimer’s Disease.


Public Domain PET image by Jans Langner (see here).

Call for Authors: If you are interested in writing an article or series of articles for this blog please write to the e-mail address below. Copyright can be retained. Index: An index of the site can be found here. The page contains links to all of the articles in the blog in chronological order. Twitter: You can follow ‘The Amazing World of Psychiatry’ Twitter by clicking on this link. Podcast: You can listen to this post on Odiogo by clicking on this link (there may be a small delay between publishing of the blog article and the availability of the podcast). It is available for a limited period. TAWOP Channel: You can follow the TAWOP Channel on YouTube by clicking on this link. Responses: If you have any comments, you can leave them below or alternatively e-mail Disclaimer: The comments made here represent the opinions of the author and do not represent the profession or any body/organisation. The comments made here are not meant as a source of medical advice and those seeking medical advice are advised to consult with their own doctor. The author is not responsible for the contents of any external sites that are linked to in this blog.


  1. It constantly is amazing to me exactly how Bloggers for example your self can find enough time and also the commitment to keep on Producing great discussions your blog is excellent and one of my personal need to read blogs, I’d been more than impressed with the blog post I simply wanted to thank you and congratulations


  2. Youre so cool! I don’t assume Ive understand anything at all like this prior to. So great to find an individual with a few authentic ideas on this particular subject matter. realy many thanks for starting this kind of upwards. this web site is a thing that’s wanted on the web, an individual having a little originality. helpful work for delivering something new to the internet!


  3. Its like you read my mind! You seem to know a lot about this, like you wrote the book in it or something. I think that you could do with some pics to drive the message home a bit, but other than that, this is magnificent blog. A fantastic read. I’ll definitely be back.


Leave a Reply

Fill in your details below or click an icon to log in: Logo

You are commenting using your account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s