Ultrasound and dynamic functional imaging in vascular cognitive impairment and Alzheimer's disease.
The vascular contributions to neurodegeneration and neuroinflammation may be assessed by magnetic resonance imaging (MRI) and ultrasonography (US). This review summarises the methodology for these widely available, safe and relatively low cost tools and analyses recent work highlighting their potential utility as biomarkers for differentiating subtypes of cognitive impairment and dementia, tracking disease progression and evaluating response to treatment in various neurocognitive disorders.



At the 9th International Congress on Vascular Dementia (Ljubljana, Slovenia, October 2015) a writing group of experts was formed to review the evidence on the utility of US and arterial spin labelling (ASL) as neurophysiological markers of normal ageing, vascular cognitive impairment (VCI) and Alzheimer's disease (AD). Original articles, systematic literature reviews, guidelines and expert opinions published until September 2016 were critically analysed to summarise existing evidence, indicate gaps in current knowledge and, when appropriate, suggest standards of use for the most widely used US and ASL applications.



Cerebral hypoperfusion has been linked to cognitive decline either as a risk or an aggravating factor. Hypoperfusion as a consequence of microangiopathy, macroangiopathy or cardiac dysfunction can promote or accelerate neurodegeneration, blood-brain barrier disruption and neuroinflammation. US can evaluate the cerebrovascular tree for pathological structure and functional changes contributing to cerebral hypoperfusion. Microvascular pathology and hypoperfusion at the level of capillaries and small arterioles can also be assessed by ASL, an MRI signal. Despite increasing evidence supporting the utility of these methods in detection of microvascular pathology, cerebral hypoperfusion, neurovascular unit dysfunction and, most importantly, disease progression, incomplete standardisation and missing validated cut-off values limit their use in daily routine.



US and ASL are promising tools with excellent temporal resolution, which will have a significant impact on our understanding of the vascular contributions to VCI and AD and may also be relevant for assessing future prevention and therapeutic strategies for these conditions. Our work provides recommendations regarding the use of non-invasive imaging techniques to investigate the functional consequences of vascular burden in dementia.
Department of Neurology, University Hospital Center Zagreb, Zagreb School of Medicine, Kispaticeva 12, 10000, Zagreb, Croatia. branko.malojcic@kbc-zagreb.hr.
Branko
B
Malojcic
Department of Psychiatry, HUG Belle-Idée, University of Geneva School of Medicine, Geneva, Switzerland.
Panteleimon
P
Giannakopoulos
Department of Neurology, Northwestern University Feinberg School of Medicine Chicago, Chicago, IL, USA.
Farzaneh A
FA
Sorond
Department of Neurology, São João Hospital Center and Faculty of Medicine of University of Porto, Porto, Portugal.
Elsa
E
Azevedo
Cerebrovascular Disease Center, Stroke Unit, University of Rome Tor Vergata, Rome, Italy.
Marina
M
Diomedi
Department of Vascular Neurology and Intensive Therapy, University Medical Center Ljubljana, Ljubljana, Slovenia.
Janja Pretnar
JP
Oblak
Department of Medical Sciences, Clinical Neurology-Stroke Unit, University Hospital, University of Trieste, Trieste, Italy.
Nicola
N
Carraro
Department of Neurology, University Hospital Center Zagreb, Zagreb School of Medicine, Kispaticeva 12, 10000, Zagreb, Croatia.
Marina
M
Boban
Department of Neurology, University of Debrecen, Debrecen, Hungary.
Laszlo
L
Olah
Department of Neurology, Charite - Universitätsmedizin Berlin, Berlin, Germany.
Stephan J
SJ
Schreiber
Neurology Clinic, Clinical Center of Serbia, Faculty of Medicine, University of Belgrade, Belgrade, Serbia.
Aleksandra
A
Pavlovic
Methodist DeBakey Heart and Vascular Center, Houston, TX, USA.
Zsolt
Z
Garami
Neurology Department, Tel Aviv Sourasky Medical Centre, Tel Aviv, Israel.
Nantan M
NM
Bornstein
Department of Neurology, Justus-Liebig-University Giessen, Giessen, Germany.
Bernhard
B
Rosengarten
D000544:Alzheimer Disease / Q000000981:diagnostic imaging* / Q000473:pathology; D060825:Cognitive Dysfunction / Q000000981:diagnostic imaging*; D006801:Humans
Alzheimer disease; Arterial spin labelling; Cerebral small vessel disease; Transcranial Doppler sonography; Ultrasonography; Vascular cognitive impairment; Vascular dementia