A prospective view on disease course and associated biomarkers in
Hereditary Cerebral Hemorrhage With Amyloidosis Dutch type (HCHWA-D)

Intracerebral hemorrhage, sporadic cerebral amyloid angiopathy and HCHWA-D
Intracerebral hemorrhage (ICH) is a frequent subtype of stroke but the research
in this field has received far less attention than ischemic stroke. Until now,
only sparse information is available on the different causes of ICH and the
factors that influence the onset of ICH, recurrence rate and outcome. Unlike
most other stroke types, the incidence, morbidity and mortality of ICH have not
declined over time.(3,4) Of the primary ICH, one third is associated with
cerebral amyloid angiopathy (CAA). CAA is characterized by the deposition of
amyloid-β (Aβ) peptide and degenerative changes in the capillaries, arterioles,
and small and medium sized arteries of the cerebral cortex, leptomeninges, and
cerebellum. Most cases of CAA are considered to be sporadic but worldwide there
are also a few familial forms of CAA. In general, hereditary forms of CAA have
an earlier onset and more severe clinical manifestations than sporadic cerebral
amyloid angiopathy (sCAA). Hereditary cerebral hemorrhage with
amyloidosis-Dutch type (HCHWA-D) is an autosomal dominant Dutch form of CAA, in
which the amyloid angiopathy is pathologically and biochemically similar to
sCAA. The disease is characterized by (repeated) intracerebral hemorrhage and
dementia. Aβ is generated by sequential cleavage of amyloid precursor protein
(APP) by alpha-, β- and γ-secretases. In the early nineties a point mutation in
codon 693 of the gene encoding the APP was found in HCHWA-D, resulting in a
Glu-->Gln amino acid substitution at position 22 of the Aβ-protein region on
chromosome 21 influencing correct cleavage.(5) HCHWA-D is considered to be a
monogenic model for sporadic cerebral amyloid angiopathy and a unique
opportunity to study the influence of vascular amyloid on ICH.

Cerebral amyloid angiopathy and MRI and CSF biomarkers
Cerebral amyloid angiopathy is associated with a high prevalence of imaging
markers of small vessel disease, including lobar cerebral microbleeds (CMB*s),
white matter hyperintensity (WMH), large perivascular spaces (PVS), cortical
subarachnoid haemorrhage (cSAH) and superficial siderosis (SS). The Leiden
HCHWA-D research group recently published new data on biomarkers in HCHWA-D. In
a 7T MRI study it was shown that microinfarcts are one of the earliest markers
of the disease, seen in 30% of presymptomatic patients.(6) Moreover a new
cortical pattern was discovered, namely a striped cortex.(7) Furthermore
vascular reactivity measured by changes in blood-oxygen-level-dependent (BOLD)
signal after visual stimulation was decreased in HCHWA-D (8). In addition, a
recent study showed both CSF Aβ40 and Aβ42 concentrations are markers of the
earliest phase of HCHWA-D related pathology before clinical or radiological
findings appear. (9)
In HCHWA-D patients, tissue changes that appear normal on conventional MRI (the
so-called normal appearing white matter (NAWM)) have not been investigated, so
far. Histopathologic studies of NAWM of non-genetic forms of small vessel
disease (SVD) have shown tissue changes consisting of lower myelin density,
activated endothelium and a looser axonal network (Gouw et al, JNNP 2011).
These MRI * invisible* changes may also occur in HCHWA-D patients and may be of
clinical relevance; using quantitative MR measurements (e.g magnetization
transfer imaging, relaxation time measurements) these changes can be
characterized in vivo.

Biomarkers, clinical symptoms and disease progression
Symptoms of HCHWA-D include (often recurrent) ICH and dementia occurring at a
relatively young age. The mean age of the first ICH is 50 years. (10) Other
clinical symptoms of CAA include headaches, migraines, and epilepsy. Previous
studies have shown that approximately 10% of ICH patients suffer from at least
one seizure after their ICH.(11) The prevalence of epilepsy in HCHWA-D is
unknown. One study suggested that epilepsy was only present in symptomatic
HCHWA-D mutation carriers with at least one ICH.(12) However, epileptic
seizures in a presymptomatic mutation carrier have also been seen in our clinic
(unpublished). Patients with a cortical (lobar) location of the hemorrhage are
especially prone to late seizures (occurring >7 days after stroke), (10) as
lobar microbleeds are often found in CAA, this finding suggests a link between
late seizures and cerebral amyloid angiopathy.
Migraine was suggested as an early symptom of HCHWA-D. (12) Headaches and
migraines in HCHWA-D patients usually start several months to years prior to
the first haemorrhage.(13) It is uncertain whether the reported migraines are
*true migraines* or caused by amyloid spells. These amyloid spells are
described as brief transient neurological episodes with symptoms which show
similarities to a migraine aura.(14)
The prevalence for seizures, headaches, migraines and other clinical symptoms
in HCHWA-D has never been studied in a truly and long lasting prospective
design. Little is known about the relation between MRI/CSF/blood biomarkers and
the clinical symptoms and signs such as future hemorrhages. A cross-sectional
study reported that the volume of white matter hyperintensities seemed to have
the closest association with cognition, and microbleeds the closest association
with symptomatic intracerebral haemorrhage.(15) Furthermore, recent data show a
correlation between MRI markers (high microbleeds count and white matter
hyperintensity volume) and CSF biomarkers (decreasing Aβ40 concentrations) in
HCHWA-D mutation carriers.(9) Longitudinal studies in this unique hereditary
CAA group are required to search for and provide support for associations
between clinical symptoms and (bio)markers and to provide biomarkers to predict
clinical outcome and treatment efficacy.

Treatment for CAA, and HCHWA-D as model for sporadic CAA
Unfortunately, currently no evidence-based treatment options are available for
CAA. With the lack of therapeutic options, clinicians are restricted to
hypertension management and avoiding antithrombotic and anticoagulant therapy
to prevent worsening of secondary injury as much as possible.
Recently, the idea was formed that HCHWA-D, as the hereditary form of CAA,
could serve as a model for sCAA based on a similar pathological and biological
basis between the two conditions. As subjects with the genetic mutation can be
identified before the onset of clinical symptoms the efficacy of disease
modifying treatments can be investigated in the earliest stage of the disease,
even before symptomatology, and the detrimental effects of amyloid deposition
in the neurovascular system could be attenuated and possibly even stopped.
Furthermore, these investigations could elucidate possible treatment effects
for the much more widely prevalent sporadic form of CAA.
In order to push the development of therapeutic strategies forward, a
prospective follow-up study with short follow-up times in a HCHWA-D cohort
seems essential. With repeated imaging, CSF and potential blood biomarkers, the
associations between clinical symptoms and disease biomarkers can be
established. These tools are crucial for the development of a treatment trial
in CAA. Therefore, in a subgroup of presymptomatic and early stage subjects
(the TRACK D-CAA subgroup) annual assessments will be performed to show how
specific markers change in the early phase of the disease, against which a
future treated cohort of patients can be contrasted to show the efficacy of new
treatments.

To follow up presymptomatic and symptomatic profiles including (early) disease
stages and (early) biomarkers of disease progression and to elucidate
pathophysiological mechanisms, we will investigate HCHWA-D patients at
different ages (both symptomatic and presymptomatic), and (where necessary)
compare them with healthy control subjects. We aim to identify characteristics
and mechanisms specific to HCHWA-D, using a unique collection of different
techniques/ methods. We will:
1. Perform an extensive clinical work-up using structured interviews and
physical examination during regular intervals to investigate long-term disease
course in HCHWA-D
2. Investigate hallmarks of amyloid function in CSF, to identify course of
amyloid and related biomarkers with disease progression
3. Investigate markers of MR- and PET-imaging and their evolution over time
with disease progression
4. Store blood and CSF of HCHWA-D patient for biobanking purposes and future
research

Our study design is a prospective cohort study. A subgroup of 50 participants
will be followed more intensively (TRACK D-CAA subgroup).

To learn more about the pathophysiology, progression and prognosis of HCHWA-D
we need to investigate HCHWA-D patients. The mutation carriers may benefit from
more insight into their disease. By investigating factors like clinical
symptoms, outcome and disease markers in prospective design we hopefully will
learn more about disease course and about the relation between MRI markers,
biomarkers in CSF, clinical symptoms and disease progression. A recent
publication emphasizes that both CSF Aβ40 and Aβ42 concentrations are markers
of the earliest phase of HCHWA-D related pathology, before clinical or
radiological findings appear. (9) It is important to identify course of
amyloid and related biomarkers with disease progression for future therapeutic
studies.
Moreover this study could eventually lead to much more insights about both sCAA
and ICH in general. Patients will be informed extensively about the potential
risks of the study procedures, after which written informed consent will be
obtained.
Blood withdrawal via venous puncture in the elbow has a very low rate of
adverse events. The needle puncture may cause bruising and in very rare cases
an infection of the skin or blood vessel may occur at the puncture site.
The risks of MRI are minimal (risk of everyday life), because there are no
consequences to the health of the participant. Potential risks from the MRI
study include movement of ferromagnetic objects in the body. Furthermore, some
subjects may feel claustrophobic in the restricted space of the MR scanner. The
most frequently occurring complication of lumbar puncture is post-punctional
headache. This may occur in 25% of patients when standard lumbar punction
needles are being used and much rarer (12%) when atraumatic spinal needles are
used. If post-lumbar puncture headache occurs, subjects should take bed rest,
drink ample water, and may use paracetamol if required. If the post-lumbar
puncture headache persists for more than a week, a blood patch may be
considered which is usually effective in treating the headache. Very rarely,
infection such as meningitis or spinal abscess may occur.
The radiation risk of [18F]Florbetaben is similar to other radiopharmaceuticals
and contributes to a patient's overall long-term cumulative radiation exposure.
Long-term cumulative radiation exposure is associated with an increased risk of
cancer. This risk is however relatively low and in our opinion outweighs the
(scientific) benefits of this study.
Also, the radiation expose for the [18F]Florbetaben PET-CT is within the limits
provided by the Nederlandse Commissie voor Stralingsdosimetrie for categorie
IIb research (see Appendix B for details and paragraph 6.4 of this research
protocol). The range of 1 to 10 mSv per year corresponds to a maximum risk of
five in ten thousand. To place this level into context, this range corresponds
to the same order of magnitude as the annual natural background radiation (per
year) in various parts of the world.