Northeast Florida Medicine
Vol. 66, No. 3 2015
43
Endovascular Neurosurgery
Introduction
Despite recent advances in management and prevention
of atherosclerotic disease, stroke remains a significant public
healthproblem. It is estimated that stroke kills nearly 130,000
Americans each year - an average of one death every four
minutes.
1,2
In addition, as many as 800,000 people may
suffer a stroke in the United States, with an estimated cost
of $34 billion per year in health care services, medications
and missed days of work.
2
According to the American Heart
Association, the vastmajority of strokes occur following acute
large vessel occlusion.
2
Currently, the only FDA-approved
medical therapy for acute ischemic stroke (AIS) is intravenous
(IV) tissue plasminogen activator (t-PA) administeredwithin
three hours of symptom onset. However, the recanalization
rates after IV t-PA for proximal large vessel occlusion (distal
internal carotid artery, middle cerebral artery, vertebral
artery or basilar artery) are suboptimal, ranging from 10
percent in the internal carotid artery to 30 percent in the
middle cerebral artery.
3
Additionally, only a small fraction
of patients with ischemic strokes are eligible to receive IV
t-PA therapy due to the narrow therapeutic window and
multiple contraindications.
In recent years, reperfusion of ischemic brain has evolved
considerably, mirroring the evolution of coronary reper-
fusion for acute ST elevation myocardial infarction. The
development of newer technologies has provided the im-
petus for neurosurgeons and interventionalists to improve
recanalization rates and restore blood flow using mechanical
recanalization systems that remove the blood clot by dif-
ferent methods. The neurovascular community has seen a
paradigm shift following an avalanche of clinical trials from
Europe and the United States demonstrating the superiority
of endovascular treatment compared to medical therapy for
patients with acute ischemic stroke.
The Concept of Ischemic Penumbra
In the early 1980s, Astrup and investigators outlined
the physiological differences between the infarct core and
the surrounding ischemic brain tissue following an acute
large vessel occlusion.
4
The ischemic penumbra represents
the tissue surrounding the infarct core and was defined as
“ischemic tissue that is functionally impaired and is at risk
of infarction but has the potential to be salvaged by reperfu-
sion and/or other strategies. If it is not salvaged, this tissue
is progressively recruited into the infarct core, which will
expandwith time into themaximal volume originally at risk.”
Timely assessment of blood flow parameters is of essence in
the initial evaluation of acute ischemic stroke to determine
the presence, volume and location of ischemic penumbra.
Computed tomography perfusion (CTP) is typically used
over other imaging modalities because it is readily available,
cost-effective and provides information regarding cerebral
blood flow (CBF), cerebral blood volume (CBV) and mean
transit time (MTT) in the acute setting (Figure 1). CBF
represents the volume of blood moving through a given
volume of brain per unit of time, with units of milliliters of
blood per 100g of brain tissue per minute. CBV represents
the total volume of blood in a given volume of brain tissue,
with units of milliliters of blood per 100g of brain tissue.
MTT represents the average time for blood to transit through
a given brain region, measured in seconds. Infarct core is
typically represented by an area of extremely low CBF and
CBV, and prolonged MTT. In contrast, the area of ischemic
penumbra is determined by decreasedCBF, prolongedMTT
and preserved CBV. Computed tomography angiography
(CTA) is also an essential part of the initial evaluation to
determine the location of vessel occlusion, collateral flow
status and coexisting pathology in other vascular territories.
2015 - New Clinical Trials
Until recently, the debate on whether patients with acute
ischemic stroke benefited from endovascular intervention
compared to IV t-PA alone was uncertain. This controversy
was particularly heightened in 2013 following the results
of three clinical trials that suggested the futility of endo-
vascular therapy in patients that received IV t-PA therapy:
the Interventional Management of Stroke (IMS) III, Local
Endovascular Therapy for Acute Ischemic Stroke
By Leonardo B. C. Brasiliense, MD
1
, Eric Sauvageau, MD
1
,
Ricardo A. Hanel, MD, PhD
1
, Philipp R. Aldana, MD
2
1
Lyerly Neurosurgery, Baptist Health, Jacksonville, FL
2
University of Florida, Jacksonville, FL
Address correspondence to:
Philipp R. Aldana, MD
836 Prudential Drive
Jacksonville, FL 32207
Telephone: (904) 633-0793
Email:
