Illustrations come from the Atelier d'Infographie of the
Medical Imaging Department of Pr Carsin in the Rennes University Hospital.
Ventricles
3D representation of ventricles
Transversal MRI slice through the ventricles
Dilatation-Enlargement : Late stages of AD ; Clinical consequence is
unknown because the enlargement only shows the cortical atrophy as well
as the global cell loss. No drug is specific of this anatomical structure
; probably the neurocytoprotective substances could prevent this enlargement.
Hippocampus
Transversal and sagittal MRI slices
Hippocampic cortex is modified at an early stage in AD, according to
the following chronology : temporal pole, amygdala ... Clinical consequence
is immediate on memory performance. Drugs which activate neurons outputs
onto this anatomical structure are, a priori, beneficial.
SUB CORTICAL LESIONS
Nucleus Basalis of Meynert
(NbM)
Coronal and sagittal MRI slices
Early modified in AD. NbM cells synthetize Acetylcholine neurotransmitter
(ACh). This ACh projects (at distance) onto many other anatomical structures.
ACh cells present, at the early stages, the histology stigmata of AD (amyloid
deposits, Neurofibrillary Tangles). The main clinical consequence is the
deficit of working memory and attention. Cholinomimetic substances act
upon this system.
OTHER SUB-CORTICAL NUCLEI
These nuclei are not systematically involved in AD. In case of specific
lesions, different clinical situations may occur : agitation, depression,
parkinsonism. Drugs specifically acting upon those systems (Noradrenaline,
Serotonin, Dopamine) will correct behavioral and psychomotor symptoms.
Locus coeruleus
Sagittal MRI slice
Site of noradrenalin (NA) synthesis, projecting particularly onto the
cortex
Mesencephalic dorsal
raphe nucleus
Sagittal MRI slice
Site of serotonin (5HT) synthesis, projecting particularly onto the
cortex.
Substantia nigra
Transversal MRI slice and 3D view of brain
Site of dopamine (DA) synthesis projecting onto the striatum (which
intervenes in automatic motor control and probably in procedural memory).
