1) The natural history of unruptured intracranial aneurysms and factors that influence treatment decisions are complex, depending on aneurysm characteristics like size and location as well as patient factors. 2) Treatment aims to completely occlude aneurysms while preserving neurological function, but options must be carefully considered based on individual patient and aneurysm assessment. 3) Scoring systems can help quantify rupture risk to inform whether conservative management or treatment is most appropriate, though ultimate decisions require multidisciplinary evaluation and discussion with the patient.

1. Dr. Shahnawaz Alam
MCh-Neurosurgery
Natural History & Surgical
Decision making of Intracranial
Aneurysms
Moderated by:
Dr. V. C. Jha
HOD, Dept. of Neurosurgery

2. • The natural history of any disease is defined as the outcome of the
disease in the absence of any intervention; its knowledge provides the
benchmarks to assess the effectiveness of treatment options.
• Defining the natural history is not just a theoretical exercise, but has
implications for patient care. The treating neurosurgeons must
evaluate not only aneurysmal but also patient factors such as age,
medical condition, and family history.

3. • It allows the neurosurgeon to make a calculated judgment about
the risks of treatment versus conservative care. This is particularly true
when dealing with a patient with an unruptured intracranial aneurysm
(UIA).
• For example, the natural history of a relatively benign UIA would favor
conservative therapy, particularly in an older patient. In contrast, a
more malignant natural history in the younger patient would make the
case for intervention more compelling and perhaps more urgent.

4. • UIAs are aneurysms with no history of subarachnoid hemorrhage
(SAH).
• Prevalence: A wide range (0.65% to 9%); This wide variation is caused
by a number of factors such as the imprecise methods for detecting UIAs,
the level of expertise of the investigators, the type of investigation (e.g.,
autopsy, angiographic, imaging), and unrecognized bias associated with
the manner of subject acquisition (i.e., the patients).
Natural History of Unruptured Aneurysms

5.  The International Study of Unruptured Intracranial Aneurysms
(ISUIA) investigators studied several groups of patients including 1449
patients with UIAs, divided into two groups: 727 patients (group 1)
who had no prior history of SAH and 722 patients (group 2) who
had a history of SAH; The mean duration of follow-up was 8.3 years.
 In group 1, the cumulative rate of rupture was 0.05% per year for
aneurysms less than 10 mm and about 1% in those over 10 mm
in diameter; Aneurysms larger than 25 mm had a 6% rupture
rate in the first year.
 In group 2, the cumulative rate of rupture was about 0.5% per year
for lesions smaller than 10 mm and about 1% for those larger
than 10 mm in diameter.

6.  In group 1, in addition to size, the location was related to
haemorrhage risk, with basilar tip, vertebral-basilar, posterior cerebral,
and posterior communicating artery aneurysms having a higher risk of
rupture; aneurysms arising from the ophthalmic portion and the
intracavernous portions of the carotid artery had a lower risk of
haemorrhage.
 In group 2, only location (i.e., basilar tip) and increasing age
predicted an increased risk of haemorrhage.
 The study, however, has been challenged on a number of grounds
related to selection bias, the retrospective nature of the study,
and the inclusion of patients with cavernous aneurysms in the
study population.

7. • Sentinel or “thunderclap” headaches are severe headaches of short
duration (approximately 1 minute) first described in 1941 by Richardson
and Hyland.
• Other than SAH, potential causes of thunderclap headaches include
reversible cerebral vasoconstriction syndrome, arterial dissection,
cerebral venous sinus thrombosis, pituitary apoplexy, intracranial
haemorrhage, spontaneous intracranial hypotension and colloid cyst.
• Subsequently, in 1958, Gillingham used the term warning leak in
recognition that such headaches may be caused by a “minor”
aneurysmal tear and resultant small haemorrhage.
• As such, these sentinel headaches could be a strong predictor of a
definitive haemorrhage. Several studies have suggested that these
warning bleeds occurred within 2 weeks with a peak within 1 day.

8. • Wall stress can be affected by a variety
of anatomic and biophysical features
such as aneurysmal shape and
irregularity, length-base ratio, orifice
size, and wall and intraluminal flow
dynamics; All these factors have been
implicated as primary or secondary
contributors to rupture risk, as has the
distance from the circle of Willis.

9. • Site: an independent variable in the incidence of SAH; Several studies
demonstrated that the relative risk of aneurysm rupture was higher
for aneurysms located in the posterior circulation, with a relative
risk of 4.1.
• Multiple aneurysms are found in approximately 15% to 20% of all
aneurysm patients; many studies have documented that multiplicity is a
risk factor for SAH.
• Most symptoms and findings associated with symptomatic aneurysms
are related to CN III dysfunctions, and the most frequent location of
symptomatic aneurysms is Pcom.
• This location has been found to have a higher rate of rupture of UIAs.
Moreover, to affect cranial nerve III function, a UIA must enlarge.

10. Natural History Of Ruptured Aneurysms
• Better defined and based significantly on randomized trials
comparing surgery with bed rest therapy.
• The results from these various studies divided into two epochs:
short-term (hospitalization to 6 months after initial SAH) and
long-term (after 6 months).
• 3-18% of patients with SAH die before hospitalization. The
variation in prehospital death rate may reflect the setting (urban
versus rural), medical retrieval system, geography, and/or the rigor in
analysing prehospital deaths.
• In addition, some studies have documented a surprisingly high rate
(25%-50%) of failure to recognize and establish a diagnosis of a
SAH.

11. Short-Term Outcome:
Post-hospitalization to 6 Months
 For hospitalized SAH patients, mortality is
associated with initial haemorrhage,
rebleeding, SAH-related complications
such as vasospasm and hydrocephalus,
and medical complications.
 For patients seen immediately after their aneurysm
ruptures, the likelihood of 1-month survival is
approximately 40%. In contrast, if a patient is not
seen for 24 hours, the likelihood of survival to 1
month is improved to 60%. If a patient does not
come to medical attention for 7 days, then the
likelihood of survival to 1 month is almost 80%.
 Molecular and Genetic Profiles: Apolipoprotein E
genotype (APOE4) would be expressed to a greater
degree in patients having an unfavorable outcome.
Apolipoprotein E is a known “injury factor
 Smoking to be positively associated with survival
after SAH.

12.  Locksley et al.; Analysis of survival
in 830 conservatively treated
patients after the rupture of a single
aneurysm.

13.  Mortality at 6M in
conservatively treated patients
is 34-39% after anterior
circulation aneurysm rupture,
approaches 50% after multiple
aneurysm rupture, and is higher
still (61%) after rupture of
aneurysms arising from the
posterior circulation.
 Rebleeding is strongly
correlated with mortality. The
rate of rebleeding is highest
during the first 24 hours and
may be particularly high during
the first 6 to 8 hours.

14.  Ohkuma et al. followed 273 patients
for 24 hours after their initial
hemorrhage and noted that 37 (13.6%)
patients had 39 episodes of
rebleeding in the ambulance or at
the referring hospital before
admission to the specialty hospital.
The peak time of rebleeding was
within 2 hours (77%), during which
the incidence was statistically
significant compared with that
occurring 2 to 8 hours after the initial
SAH bleeding (P < .01).
 They also found that rebleeding
occurred more frequently in
patients with a poor grade, with
intracerebral, subdural, or
intraventricular hematoma and
systolic arterial pressure above 160
mm Hg.

15. Late Rebleeding
• Long-term studies revealed that
aneurysms do not heal.
Instead, long-term follow-up
documented a persistent
yearly rebleeding rate of
approximately 3%.

16. Late Mortality
• The overall mortality associated with a late hemorrhage
approximated 60%. The mortality rate of 60% is similar to that
observed during the acute period (0-6 months) when the prehospital
deaths are included.
• It is interesting that 18% of the patient who experienced rebleeding
late died before they could be hospitalized.
• Over the course of decades of follow-up, the majority of deaths were
related to fatal rebleeding, which occurred at a yearly rate of 2%
to 3%; The primary cause of non-SAH-associated deaths was
cardiovascular disease.
 Late Epilepsy: The development of late epilepsy in the conservatively
treated patients was high and varied with the location of the ruptured
aneurysm: respectively, 5%, 10%, and 25% of patients with ruptured
anterior, posterior, and middle cerebral aneurysms developed
epilepsy over the course of many years of follow-up.

17. Surgical Decision
making of
Intracranial
Aneurysms

18.  Strategies to decrease mortality:
1. Early diagnosis (Identification of aneurysms before they rupture);
2. Aneurysm repair and in particular decision making regarding
which patients should undergo aneurysm repair, the timing of
repair, and technique of aneurysm occlusion; and
3. Intensive care.
 Two important goals in the treatment of intracranial aneurysms.
1. The first is complete, permanent aneurysm occlusion.
2. The second goal is optimal preservation or restoration of the
patient’s neurological function.

19.  Selecting the appropriate treatment can be a complex process and
is best achieved by a team of neurovascular and endovascular
surgeons after careful evaluation of the patient’s clinical
presentation and associated comorbidities, consideration of the
natural history of the aneurysm, and thorough review of the
radiographic studies to understand the aneurysm’s morphology and
the patient’s vasculature.
 In addition, the safety and efficacy of the treatment options and
skill and experience of the practitioners need to be considered.

20. DECISION MAKING
The Status of the Patient and Aneurysm Natural History
• Patient age and comorbid conditions;
• Aneurysm morphology, lesion size, and location; whether the
aneurysm is intact or ruptured; associated factors such as ICH, IVH,
and clinical grade after aneurysm rupture;
• Endovascular versus microsurgical accessibility/suitability and
long-term angiographic outcome; and
• Expected recovery duration and require long-term follow-up.

21. Neuroradiologic Evaluation
• CTA/MRA(complement or alternative )/DSA(Gold standard)
• CTA has a low sensitivity for aneurysms <5 mm in size, are adjacent
to bony structures.
• For surgical planning, CTA with 3D reconstructions, four-dimensional
CTA and volume rendering, and spin, rotational, and 3D DSA data in
an orientation that reproduces the neurosurgeon’s intraoperative view are
valuable adjuncts.
• 3D printing technology can also be used to help plan or facilitate
surgical or endovascular techniques. This is particularly useful for large
and complex aneurysms.

22. • A combination of imaging techniques often is necessary, particularly
for more complex aneurysms.
• Used for accurate preoperative planning and a full understanding
of the relevant anatomy.
• Critical in determining timing (e.g., presence of intracerebral clot in a
poor-grade patient), selection of treatment options (e.g.,
endovascular versus open surgery), and surgical approaches (e.g.,
low-lying versus high-lying basilar tip aneurysm; atretic A1 segment in
an anterior communicating artery aneurysm).

23.  The following features need to be evaluated:
 The aneurysm’s parent vessel; size, shape, and relationship
to parent and adjacent arteries; neck size and regularity
 Presence and location of vasospasm; Adjacent vessel
displacement consistent with mass effect (e.g., partial aneurysm
thrombosis [i.e., the aneurysm is larger than that seen on DSA])
 Presence of other aneurysms or vascular abnormalities.

25. • Scoring systems such as PHASES (population, hypertension, age,
size [of the aneurysm], earlier SAH, site [aneurysm location]) and
ELAPSS (earlier SAH, aneurysm location, age, population, aneurysm
size, and shape): to “quantify” rupture risk and so aid in decision
making about UIA treatment.
• An increase in the PHASES score predicts a greater 5-year rupture
risk: 3 points or less, 0.7%; 5 points, 1.3%; and 10 points, 5.3%.

26. Efficacy of Surgical Treatment for UIA:
• Meta-analytic studies suggest that the
cumulative 10-year risk of retreatment
or rupture is 3.0%.
• To treat a recurrent aneurysm after clipping
is sparsely reported in the literature.
• In carefully selected patients, flow-
diverting stents may be used for
complex aneurysms that recur after
surgery.
Factors That Are Associated With Surgical Outcome
• Increased aneurysm size is the most important factor associated with
inability to occlude the aneurysm
• Overall, aneurysm size >25 mm has a fourfold increased risk compared
with a 5-mm aneurysm.

27. • UIA management should be tailored to the patient’s risk and the
physician’s own experience.
• In addition, consideration of patients’ psychosocial profiles and how
the knowledge that they have an aneurysm affects them should be
considered because studies suggest that quality of life is compromised
in patients who have an untreated UIA.
• Studies also suggest that poor quality of life because of headaches can
be improved after UIA surgery, although many variables can affect
this outcome.
• Microsurgical, endovascular, and alternative strategies such as vessel
occlusion with or without bypass or no treatment other than observation
and clinical follow-up should be considered, specific to the patient and
the UIA.

28. Calculation of surgical risk for UIA
(A) Point values to grade surgical risk for unruptured aneurysms. (B) Histogram illustrating
illustrating that grade, which is determined by adding the point value for each factor, is
factor, is strongly associated with surgical outcome.
 Khanna et al.; Incidence of poor outcomes progressively increased from 0% in grade 0
patients to 66% in grade IV patients.

29.  Based on the available literature, the following UIA patients
should be treated:
1. SAH from another aneurysm,
2. A symptomatic aneurysm,
3. Aneurysms >7–10 mm in nearly all patients with a life
expectancy of 12 or more years, and
4. Aneurysms >5 mm if the patient is young or middle-aged.
• These recommendations depend on collaboration among a highly
experienced cerebrovascular team of microneurosurgeons and
endovascular neurosurgeons at a medical center with a high case
volume.
• AHA guidelines suggest that a “high-volume” center performs
>20 UIA procedures each year.

30. • Meta-analytic studies suggest that the overall outcome for UIAs
treated with endovascular or microsurgical techniques are
similar, thus emphasizing the need for selection on a case- by-case
basis.
• Small, incidental UIAs (<5 mm in diameter) should be managed
conservatively in most cases; the exception is when there is a
positive family history; patients who smoke and are hypertensive.
• In select patients when both treatment and natural history carry
very high risks (e.g., those with giant aneurysms or advanced
age), nonoperative management also may be elected.
• When aneurysm occlusion is not recommended, patients should be
counseled about risk factors and serial imaging (CTA or MRA; 6–
12 months).

31. Unruptured intracranial aneurysm treatment score
(UIATS) model
• This model includes and quantifies the key
key factors to help clinical decision making for
UIA management.
• The model was developed using a Delphi
consensus process and validated in a subsequent
prospective study.
• To calculate a management strategy:
observation Vs aneurysm occlusion (either
surgical or endovascular)- the number of points
points for each variable are summed.
• This will lead to two numerical values, one that
one that favors UIA repair and another that
favors observation.
• When the difference exceeds three or more
more points, one strategy may be preferred over
the other.
*Adapted from Etminan N, Brown RD Jr, Beseoglu K, et al. The
The unruptured intracranial aneurysm treatment score: a
multidisciplinary consensus. Neurology. 2015;85:881–889.)

32. RUPTURED ANEURYSM
• Outcome after SAH is influenced by many variables that may be
specific to the patient, the aneurysm, the institution, and/or
geography (urban Vs rural).
• Timing of aneurysm occlusion to prevent rebleeding, and
management of factors such as poor clinical grade, ICH, IVH, and
vasospasm, which can all adversely affect outcome-need to be
considered in the decision-making process for each individual patient.

33. Aneurysm Rebleeding
• 70-90% of patients who rebleed die. Hence, it is currently the most
treatable cause to avoid poor outcomes and is a determinate factor
in treatment timing.
• Untreated, between 20%-30% of aneurysms re-rupture within the
first 30 days and then at a rate of approximately 3%-5% per year.
• The risk of rebleeding is greatest on day 1 and in the first 6 hours
after SAH.
• Rates between 4%-15% are described for the first 24 hours. It may
also complicate about 10% of patients in the ambulance or at the
referring hospital before admission to the treating hospital.
• Rebleeding then occurs at a constant rate of 1%-2% per day during
the subsequent 4 weeks.

34. Timing of Aneurysm Obliteration
• Early surgery eradicates the risk of rebleeding and appears to be
associated with improved outcome.
• Today efforts are made to perform aneurysm occlusion within 24
hours or even within 6 hours of admission.
• Formal institutional protocols are required to facilitate this, and single-
center series suggest that “ultra-early” aneurysm obliteration (<24
hours) can help improve outcome by eliminating rebleeding or
reducing the risk of vasospasm and hydrocephalus.
• The effect on rebleeding is more pronounced for coiling than
clipping.

35. • Other studies have found that this timing difference may not apply to
patients who undergo endovascular aneurysm occlusion, unless they
are in poor clinical grade, in whom ultra-early (<24 hours) endovascular
occlusion may be preferable.
• Ultra-early endovascular embolization for ruptured cerebral aneurysms
under systemic anticoagulation increases the risk of ICH growth
unrelated to aneurysm rebleeding.
• Single-center studies suggest that care in a modern intensive care unit
rather than ultra-early surgery reduces the rebleeding risk.
• However, the role of ultra-early surgical or endovascular occlusion
requires further rigorous study (e.g., <12 hours versus <1 day versus
1–3 days versus >3 days).

37. Poor-Grade Patient
• Between 20%-40% of patients admitted to a hospital after SAH are in
poor clinical condition (Hunt and Hess grades IV and V).
• Epidemiologic studies demonstrate that up to 15% of the patients die
before reaching the hospital and 30% die within the first 48 hours of
aneurysm rupture.
• Published data suggest that an aggressive policy may provide these
patients with their best chance of recovery, including in those up to 80
years of age.
• An aggressive approach requires an organized, multidisciplinary,
proactive critical care approach that starts with in-the-field resuscitation

38. • It includes rapid cardiopulmonary and neurological resuscitation
and transport to a hospital, intracranial pressure (ICP) control,
early aneurysm occlusion (surgical or endovascular), prophylaxis
against delayed cerebral ischemia, and care in a dedicated
neurocritical care unit.
• Under these circumstances, favorable outcomes and reduced short-
term mortality may be observed in 50%-60% of poor-grade patients,
particularly those with anterior circulation aneurysms.
• Patients with elevated ICP (particularly >50 mm Hg) who respond to
mannitol often may do well, whereas those who do not respond to
osmotherapy inevitably have a poor outcome.

39. • Some poor-grade patients may benefit from a decompressive
craniectomy either at the time of surgery to clip the aneurysm or
remove an ICH, or following endovascular aneurysm occlusion.
• The time from onset of intractable ICP to decompressive
craniectomy seems to be crucial, rather than the time from SAH to
decompressive craniectomy; that is, sooner is better.
• A single-center studies suggest a more favorable outcome with early
primary decompressive craniectomy, particularly if there is an ICH,
rather than delayed secondary decompressive craniectomy.

40. • Endovascular occlusion of the acutely ruptured aneurysm is an
attractive alternative to surgery for poor-grade patients without an
ICH when extensive cerebral swelling is seen on CT scan or ICP is not
controlled.
• In general, microsurgery or endovascular treatment should be selected
primarily according to angiographic features.
• EVT for poor-grade patients may be physiologically less stressful
because brain retraction and vessel dissection are not required.
• Indeed, perioperative GCS score decline is less frequent in SAH
patients who undergo endovascular coiling than surgery.
• Ideally an EVD device should be placed before endovascular occlusion
is attempted.

41. Intracerebral Hemorrhage
• ICH complicates about 30% of ruptured aneurysms, and increases
mortality after SAH.
• Clinical series demonstrate a tendency for the improved patient
outcome when emergency ICH evacuation is performed, particularly
with simultaneous, successful aneurysm obliteration.
• Factors such as young age, better clinical grade, small ICH volume
(<25–50 mL), and intrasylvian ICH are associated with a better
outcome, whereas a decreasing percentage of ICH evacuations, IVH,
and need for EVD aggravate outcome.

42. • During surgery for aneurysmal ICH, large bone flaps are preferable to
prevent brain herniation and strangulation and provide easy access
to the ICH.
• Brain relaxation using mannitol or hypertonic saline is important.
Similarly, the sphenoid wing and orbital roof should be drilled down
to reduce brain retraction.
• During the closure, lobectomy, EVD, or dural augmentation without
bone replacement may be necessary if cerebral swelling persists.

43. Acute IVH and Hydrocephalus
• Acute HCP (ventricular enlargement within 72 hours) and IVH often are
observed after aneurysm rupture, particularly in poor-grade patients and
those with thick subarachnoid blood on CT, although increased ICP
also is seen in as many as 50% of good-grade patients.
• EVD is recommended, particularly when the patient has depressed
consciousness: 40-80% have some degree of improvement after the
procedure.
• Several clinical series describe good results using EVD for
hydrocephalus or IVH following aneurysm rupture provided early
aneurysm occlusion is achieved.
• The role of intraventricular rTPA (2 mg every 12 hours) has been
investigated in small RCTs. These studies show that its use is feasible and
is associated with a more rapid reduction in IVH and a reduced need for
shunting; However, an increased risk of infection (meningitis and
ventriculitis).

44. • Chronic or delayed hydrocephalus is observed in about 25-30%
of patients who survive aneurysm rupture and usually develops within
a year of SAH.
• Half the patients with acute hydrocephalus eventually require a
ventriculoperitoneal shunt.
• Factors associated with hydrocephalus include older age,
increased ventricular size, and IVH at admission, as well as fourth
ventricular blood, poor clinical grade, pre-existing hypertension,
alcoholism, female sex, increased aneurysm size, ruptured anterior
communicating artery aneurysm, pneumonia, meningitis.

45. Ruptured Aneurysms and Early Vasospasm
• Vasospasm is associated with the poor outcome; between 10-15% of
patients will have angiographic evidence of vasospasm within 48 hours
of aneurysm rupture.
• Recent experimental and clinical observations suggest that surgical
manipulation of blood vessels may not exacerbate the arterial
narrowing seen after SAH.
• Simultaneous coil embolization and mechanical or pharmacologic
angioplasty (e.g., continuous nimodipine infusion during the
embolization procedure) may be used.

46. Algorithm illustrating
management approach to poor-
grade (Hunt and Hess grade IV or
V) aneurysm patients
 Modified from Le Roux P, Winn HR. The
poor grade aneurysm patient. Acta
Neurochir Suppl. 1999;72:7–26.)

47. SPECIAL CIRCUMSTANCES
• A variety of special circumstances may alter the management approach
in patients harboring cerebral aneurysms.
• These include pregnancy; aneurysms in children or the elderly;
aneurysms associated with infection, trauma, AVMs, or carotid artery
disease; and fusiform, giant, cavernous, residual, or
microaneurysms.

48. Pregnancy
• When a UIA is discovered during the first trimester, surgery should
ideally be deferred until the second trimester, in part to reduce potential
drug teratogenic effects during treatment.
• A cesarean section may be preferable when a UIA is discovered
late in pregnancy, particularly if the aneurysm becomes symptomatic
or has enlarged.
• Evidence-based guidelines for SAH in pregnancy are lacking. In
general, pregnant patients with ruptured aneurysms are treated
the same as nonpregnant women and in a multidisciplinary
approach.
• Aneurysm management should be based on neurosurgical
considerations, whereas obstetric management should be based
on SAH severity and gestational age.

49. • During surgery, temporary clips rather than hypotension are
preferred to reduce the risk of fetal hypoperfusion.
• Similarly, care should be taken when mannitol is administered
because its use can lead to maternal hypoperfusion and subsequent
uterine hypoperfusion, or fetal hyperosmolality.
• If an aneurysm rupture occurs during labor, simultaneous craniotomy
and cesarean section may be necessary; the cesarean section
should be performed first so that the fetus is not exposed to prolonged
anesthesia.

50. Pediatric Aneurysms
• Aneurysms in children are rare and differ from those found in adults.
• For example, posterior circulation, dissecting, giant, infectious, and
traumatic aneurysms are more frequent in children.
• Multiple aneurysms are less frequent but may occur in syndromic
settings.
• In addition, cervicocerebral arterial tortuosity, a marker of congenital
arteriopathy, is more frequent and may correlate with aneurysm growth
and rupture.

51. • Growth over time, however, appears to be infrequent and slow.
• For some giant, complex aneurysms, parent artery occlusion or
extracranial-to-intracranial (EC-IC) bypass may be the best
treatment choice.
• Endovascular treatment of pediatric aneurysms, using both
reconstructive and deconstructive techniques, appears to offer better
short-term clinical outcomes; however, the long-term durability of
endovascular treatment is still unclear.
• Flow diverters (e.g., the Pipeline Flex embolization device [PED];
ev3/Covidien), while approved for adult use, can be used safely in
select children.

52. Infective Aneurysms
• 2-6% of intracranial aneurysms in adults; These lesions often are
associated with infective endocarditis, intravenous drug abuse, or
immunologic compromise, and can develop rapidly.
• Fungal infections, particularly aspergillosis and candidiasis, may be
associated with proximal ICA aneurysms.
• Aneurysms associated with bacterial infections, most commonly
streptococci and Staphylococcus aureus, usually are located on distal
MCA branches.
• All infective aneurysms require 4-6 weeks of culture-directed
antimicrobial therapy whether the aneurysm is occluded or not.

53. • In some patients this may be sufficient, and up to 30-50% of infective
aneurysms may resolve or decrease in size. However, the lesions
require close follow-up with serial angiography, preferably DSA, and
blood cultures.
• MRI findings such as microbleeds, susceptibility-weighted
imaging of lesions, or contrast enhancement may be helpful.
• Studies suggest that mortality with conservative treatment is nearly
two fold greater for conservatively managed patients (26.7%)
than those who underwent clipping or embolization (15.1%); This
difference, however, may reflect the severity of cardiac disease and
the role that anticoagulation plays during cardiac surgery.

54.  Decisions about surgery (or endovascular
intervention) are driven by five primary variables:
1. Aneurysm rupture or not,
2. ICH and ICP,
3. Parent vessel relationship to eloquent cortex,
4. Cardiac status, and
5. Need for cardiac intervention and anticoagulation.

55. • Surgery rather than endovascular occlusion has traditionally been
preferred for infective aneurysms for fear of placing a “foreign body” in
an infective lesion that is friable.
• Furthermore, many infective aneurysms are located more distally
and may not always be accessible to direct endovascular
techniques.
• However, accumulating evidence suggests that endovascular
embolization (e.g., with n-butyl cyanoacrylate), covered stents,
direct stent coiling, or even flow-diverting stents can be effective
and safe treatment modalities in select cases of infective
aneurysms.

56. • Indeed, EVT may be ideal when parent artery occlusion rather than direct
aneurysm occlusion is contemplated and when anticoagulation is required for the
cardiac disease.
• When surgical aneurysm occlusion is required, any hemodynamically
significant cardiac lesion should ideally be corrected before aneurysm
obliteration.
• However, when the aneurysm is associated with an abscess or a hematoma,
aneurysm surgery may be necessary first.
• During surgery, the surgeon must be prepared for aneurysm excision and
parent vessel anastomosis, bypass, or a ligation procedure.

57. Traumatic Intracranial Aneurysms
• < 1%; TICAs usually are associated with penetrating head injury or
contiguous skull fracture and are more common after stab wounds
or low-velocity shrapnel injuries in the MCA region.
• In nonpenetrating head injury, distal anterior cerebral TICAs may
develop when there is falcine herniation and should be suspected
with delayed corpus callosum ICH.
• Unstable and have a high rate of rupture; approximately 50% may do
so within the first 7–10 days after injury and up to 90% within 3
weeks of injury.

58. • Conventional DSA is the diagnostic gold standard to detect
TICAs and is recommended within 7–15 days of penetrating head
injury, and if negative, is repeated 7 days later when the risk of
an aneurysm is high.
• High-quality CTA is reasonable but may miss small TICAs.
Histologically most TICAs are false aneurysms and so
endovascular techniques were traditionally not considered a
permanent solution.
• However, recent studies suggest coil or stent-assisted coil (SAC)
embolization with parent vessel preservation is possible in up to
50% of lesions. Similarly, use of flow diverters such as the PED for
endoluminal reconstruction of the damaged vessel wall is feasible.

59. Fusiform Aneurysms
• Occur most frequently at the skull base, particularly in the
vertebrobasilar circulation, but may also involve the proximal carotid
artery or MCA.
• Characterized by circumferential dilation, elongation, and
tortuosity of cerebral arteries without an aneurysm neck and are
associated with atherosclerosis and dolichoectasia.
• The vessel dilation can cause turbulence, damage to branching
vessels, and thrombus formation.
• The majority of patients with fusiform aneurysms have ischemic
symptoms.
• In these patients, provided there is no SAH, antiplatelet therapy or
anticoagulation may improve the outcome.

60. • Require treatment or occlusion, if growth occurs, causing symptoms
through compression, or if rupture occurs. An initial diameter >10 mm
in fusiform aneurysms predicts a greater risk of future rupture or
growth.
• Despite advances in surgical and endovascular techniques, fusiform
aneurysms remain a therapeutic challenge.

61. Suggested treatment algorithm for
patients with intracranial hemorrhage
and both an arteriovenous malformation
(AVM) and an aneurysm.
 (From Cockroft K, Thompson RC, Steinberg GK.
Aneurysms and arteriovenous malformations.
Neurosurg Clin North Am. 1998;9(3):565–576.)

62. Microaneurysms (Blister Aneurysms)
• < 3 mm in diameter and typically occur along the ICA; often broad-
based relative to their height and so can be difficult to occlude using
direct clipping or coils.
• In addition, they are fragile and have a propensity to rupture during
manipulation, hence the optimal treatment is still to be defined.
• Unruptured microaneurysms, particularly if asymptomatic, require close
follow-up.
• Alternatively, bypass and trapping can eliminate the diseased segment
and avoid direct aneurysm manipulation during surgery.
• Following SAH, early bypass and trapping are feasible and appear
preferable.

63. • Several studies suggest that endovascular techniques such as single or
multilayer flow-diverting stents, Onyx (Covidien), covered stents, or
stent-assisted coil embolization are promising strategies.
• Interestingly, the risk of periprocedural rupture is higher for blister
aneurysms (8.3%) than larger aneurysms.
• Combined techniques such as microsurgical clip wrapping immediately
after SAH and delayed deployment of a flow- diverting stent may help
improve long-term durability and avoid hemorrhagic complications
associated with antiplatelet agents in the acute phase after aneurysm
rupture.
• Early experience with flow diverters (e.g., PED), allowing vessel
reconstruction, shows complete occlusion in nearly 90% of cases.

64. Giant Aneurysms
• 25 mm; about 4%; The risk of rupture is >10% per year and,
untreated, the 5-year mortality of giant aneurysms is 60-100%
because of stroke or hemorrhage.
• Despite advances in microsurgery and imaging and the development of
new endovascular techniques, the treatment of giant intracranial
aneurysms remains a challenge because it is difficult to visualize and
accurately separate the parent artery and aneurysm neck.
• Three treatment goals: prevention of aneurysm rupture, restoration or
preservation of flow, and relief of mass effect.
• Factors such as anatomic location, perianeurysmal angioanatomy
(e.g., branch vessels and perforators), neck width, intraluminal
thrombosis, aneurysmal wall atherosclerotic plaques and
calcifications, collateral circulation, and previous treatment need to
be considered.

65. • Several shortcomings are associated with endosaccular coil
embolization of giant aneurysms, in particular recanalization (hence a
need for additional procedures and associated risk) and thromboembolic
events.
• Consequently, appropriate microsurgical procedures, in experienced
hands, have been considered as first line in the management for
large and giant intracranial aneurysms, especially those with complex
anatomy, wide neck, mass effect, partial thrombosis, and the presence of
critical perforating vessels from the aneurysm wall. The exception,
however, may be basilar aneurysms.
• Surgical techniques also have long-term durability and may better
reduce aneurysm volume and mass effect.
• The evolution of flow diverters, however, has transformed giant
aneurysm endovascular management. It is important to recognize that
surgical and endovascular approaches are not separate but are best
viewed as complementary and supplementary and in many giant
aneurysms may be used in combination.

66. • Proximal and distal vascular control (surgical or endovascular) is
important during repair of giant aneurysms; it permits reduction of
aneurysm size and so improves visualization of the surrounding
anatomy.
• Similarly, an aneurysm with intraluminal thrombosis can be opened and
the clot removed (tulip technique). A mass reduction clip placed on
the dome to decompress it, or suction decompression, may also
facilitate neck visualization.
• Cerebral protection, such as barbiturates, is necessary. Skull base
techniques facilitate vascular control. For some proximal ICA giant
aneurysms, exposure of the cervical or petrous carotid artery may be
helpful, whereas endovascular techniques, hypothermic circulatory
arrest, or adenosine-induced asystole may be useful for posterior
circulation giant aneurysms.

68. Summary
• The natural history is affected by multiple factors, both patient and aneurysm
related.
• Patient characteristics include age, gender, blood pressure, lifestyle (smoking,
alcohol use), metabolic and genetic factors, and sentinel haemorrhage.
• Aneurysm characteristics associated with rupture include size, configuration,
location, multiplicity, growth, hemodynamic factors, and possibly inflammation.
• Hemorrhage from a ruptured aneurysm is highly lethal, with an early death
rate associated with the initial event and rebleeding.
• There are a number of factors related to the aneurysm and to the patient that needs
to be considered when treating a patient with a ruptured aneurysm.
• Long-term survival after a SAH does not provide protection against
rebleeding

69. • The primary goal of intracranial aneurysm treatment is complete
permanent aneurysm occlusion and parent artery preservation.
• Intracranial aneurysms can be occluded using microsurgical or
various endovascular techniques, the appropriate selection of
which requires a collaborative approach among members of the
cerebrovascular
team, including microneurosurgeons, endovascular neurosurgeons,
and neuroradiologists, and an understanding of the anatomic, physical,
and physiologic characteristics of both techniques.

70. • Patient-specific and aneurysm-specific factors, including careful
evaluation of the patient’s clinical presentation and associated
comorbidities, consideration of the natural history of the aneurysm, and
thorough review of the radiographic studies to understand the
aneurysm’s morphology and the patient’s vasculature, should be
carefully analyzed before treatment.
• In general, endovascular techniques are associated with better
short-term outcomes, whereas surgical techniques are more durable
and associated with better aneurysm occlusion and less rebleeding.
• For complex aneurysms, surgical or endovascular approaches are
best viewed as complementary and supplementary and often can be
used in combination. However, the recent introduction of flow-diverting
stents has significantly enhanced the ability to treat many complex
aneurysms.

71. References:
• Youmans and Winn neurological surgery 8th edition
• Ramamurthi & Tandon's textbook of neurosurgery 3rd edition
• Internet
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