Outline of
Neurosurgery
E. R. Flotte, 2008
Please send comments
and corrections to admin@flotte2.com
Radiology
Blood on
MRI: (T1/T2) <24h (oxyhemoglobin):
iso/iso. 1-3d (DeoxyHgb):
iso/hypo. 3-14d (intracellular metHgb): hyper/hypo. >14d (extracellular
metHgb): hyper/hyper.
hemosiderin:
hypo/hypo
Angiogram: 0.5% risk of stroke, 7%
w/atherosclerosis
Cerebral Aneurysms
·
·
Other types of aneurysms:
o
Oncotic
aneurysms: most common with left atrial myxoma, choriocarcinoma
o
Fusiform
o
Mycotic
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Prevalence 1-6%. Komotar RJ
N1/08: 1% overall, 1% in young, 4% in elderly. 20-30% multiple.
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Pcom (35%)
> Acom (30%) > MCA (20%) > basilar tip (5%).
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Risk factors: age, smoking
(3-10x), heavy alcohol use, HTN (3x), ?hormones
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Predisposing factors: Aortic coarctation, AD polycystic kidney disease, fibromuscular dysplasia, Marfans, Ehlers-Danlos, homocystinuria, NF1, AVMs
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Rupture risk:
o
ISUIA
(International Study of Unruptured Intracranial Aneurysms NEJM 12/10/1998):
Retrospective. Risk for aneurysms <10mm = 0.05%/yr. For >10mm = 1%/yr. (0.5%/yr
in those with previous rupture from another aneurysm).
o
Other
studies refute this (rupture rate 1-2%/yr) (Juvela, Mocco, Rinkel). Some feel ISUIA selected for low-risk lesions
since high-risk lesions were treated and withdrawn.
o
ISUIA Part 2 (Wiebers DO, Lancet 7/12/2003), prospective: <7mm, 7–12mm,
13–24mm, and >25mm yearly rupture rates were 0.15%, 1.2%, 3.1%, and 8.6%. (<7mm with previous SAH was 0.4%)
§
5-year rupture rates for anterior
circulation: 0, 2.6, 14.5, and 40%, posterior circulation: 2.5, 14, 18.4, and
50% (no history of SAH).
·
Rupture risk increased with: Large size (no critical
size), high dome/neck ratio, high aspect (aneurysm depth:neck width). Smaller
aneurysms produce more extensive SAH (JN8/03). Slow flow increases rupture
risk.
·
If two or more family members
have aneurysms, others should be screened by MRA or CTA (5-10% positive).
Frequency is debated (every 6mos to 5yrs) (N8/03)
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Blood-blister aneurysms: thin-walled, no neck, fragile, rupture during surgery, on nonbranching supraclinoid
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Complications:
o
Rerupture: 4% 24hr, 20%
2wks, 50% 6mos, then 3%/yr. Unruptured 1-2% (<10mm 0.5%).
o
Vasospasm: See
below.
o
Hydrocephalus:
10% require shunting.
§
No
difference in shunt placement between gradual and rapid EVD weaning (JN2/04)
§
Effect
of increased ICP on outcome unproven (JN9/04)
o
Seizures:
§
Seizures after SAH is 5 to 8% (Rosengart AJ JN 8/07)
§
Based on meta-analysis of 4 RCTs, prophylactic AED usage after SAH was significantly
associated with worse outcome at 3 months, development of cerebral vasospasm,
neurological deterioration, and cerebral infarction as well as elevated
temperature during hospitalization. Use may be justified in high risk patients
(cortical injury, unsecured aneurysms) (Rosengart AJ
JN 8/07)
o
Cardiac: elevated cardiac enzymes
and EKG changes common. MI.
·
Diagnosis:
o
CT. If CT is negative then LP.
If CT and LP negative then consider angio (LP may be negative with loculated blood)
o
Cerebral angiogram: 4 vessel
- gold standard. Risk of hemorrhage 3% with SAH.
§
Must see both PICA origins to be adequate
§
May need carotid compression to visualize flow
through Acom from both ACAs
o
MR angio: False-positive
and false-negative rates 10%.
o
CT Angio: Sensitivity/specificity >95%
for aneurysms >7mm. Look for neck calcification
or plaques. Especially beneficial for emergent ICH evacuation.
§
With SAH: If aneurysm seen it is reliable. Perform
angio to confirm (-) CTA.
§
No SAH: If (+) consider angio to confirm small
aneurysms. If (-) then probably reliable.
·
“Angiogram-negative” (or “Occult”) SAH
o
10% of SAH. Most common cause
is non-visualized aneurysm due to aneurysm thrombosis or inadequate study.
o
Other causes: Perimesencephalic SAH, spinal or
cerebral AVM, sickle cell, pituitary apoplexy, cocaine, arterial dissection,
“SAH of truly unknown cause”
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Spontaneous thrombosis of
aneurysms may occur (10% of autopsy series); however they may reappear and
rupture years later.
o
Acom is most common location.
o
Hemorrhage rate is 0.5%/year (lower than angiogram
(+) SAH). Other SAH complications occur (vasospasm may be less likely).
o
Consider repeat angiogram at 10-14 days. Overall
2-25% positive yield on repeat angiogram, but up to 70% with interhemispheric
SAH.
o
Surgical exploration has been advocated by some,
especially if re-bleeding occurs or if the SAH is in a typical aneurysm
location (interhemispheric, Sylvian fissure)
Treatment
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Unruptured:
o
See Neurosurg Focus 11/04 (Spetzler, Dacey et al)
o
Aneurysms >10mm generally merit
treatment if reasonable risk
o
ISUIA:
<10mm = 0.05%/yr rupture rate does not justify surgery. Advocated by AHA
Stoke Council (2000).
§
Other
studies refute this (rupture rate 1-2%/yr).
Most aneurysms with SAH are <10mm.
§
Heros feels <5mm should rarely be treated (only if very young). 5-9mm
controversial. (citation pending – comment in JN)
o
Komotar RJ N1/08: symptomatic unruptured
aneurysms generally should be treated; incidental aneurysms < 5 mm should be
managed conservatively; aneurysms > 5 mm in patients younger than 60 years
of age should be seriously considered for treatment; incidental aneurysms >
10 mm should be treated in nearly all patients younger than 70 years of age;
o
Growth (>1mm), shape
(multilobulated, “tits”), genetic conditions, previous SAH from another
aneurysm may increase rupture rate
·
With ICH: Higher rebleed
rates than pure SAH. Clot evacuation alone mortality 75-100%. Must secure
aneurysm. Consider coiling then evacuation.
·
E-ACA (ε-aminocaproic acid, Amicar): Inhibits plasminogen→plasmin
(digests fibrin). Rebleeds decreased from 20% to 12%,
but vasospasm increased from 23% to
32%, hydrocephalus increased, mortality unchanged. Consider in non-surgical
patients.
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Poor Grade
(Hunt-Hess IV or V) controversial. Some favor early treatment because a subset
will have good outcome.
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Seizures with unruptured aneurysm usually treated
with clipping and removal of aneurysm without extensive cortical resection. Not
clear if coiling improves seizures.
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Ruptured: Airway and hemodynamic
stabilization, control BP, ventriculostomy/LD for hydrocephalus, Nimodipine, analgesics, consider AEDs
(until secured - see above)
Surgery
o
Timing: earlier
generally favored in H/H I-III, but late has some advantages. See ICSTAS
(International Cooperative Study on the Timing of Aneurysm Surgery,
o
Use mannitol, CSF drainage, mild hypothermia (33-36º). Keep SBP
<140 until clip placed.
o
Hypothermia: IHAST
study showed no benefit, increase in bacteremia (NEJM
1/13/05)
o
Some routinely
fenestrate the lamina terminalis to prevent hydrocephalus
o
Consider microdoppler, MEPs (more
sensitive than SSEPs).
o
Previously
coiled aneurysms: do not remove coils if placed >3mos previously. <6mos
removal is controversial.
o
Options for
angiography include: routine intraoperative,
selective intraoperative, and routine postoperative.
§
Intraoperative angiogram:
Estimated to avert serious complications in 2-10% of patients (JN2/04,JN6/02,N11/04). Complications 0.5-2.5%.
§
Indocyanine green video
angiography also an option.
o
Temporary
occlusion: normotension,
Etomidate (0.3mg/kg) or propofol
to burst suppression (Barbs cause hypotension, but pentobarb
is used). Less likely to be tolerated w/MCA aneurysm (26% infarction, versus 9%
with
o
Neck avulsion: wrap with cotton then apply clip
(JN11/03)
Coiling
o
Cranial nerves deficits usually improve post-coiling.
o
Timing of coiling does not affect procedural
morbidity or outcome.
o
Measure dome-to-neck ratio
o
Coil types: 3-D, complex fill, biologically active.
o
Balloon remodeling for wide-necks. Stenting for
wide-neck & fusiform.
o
5-10% morbidity, 2% mortality. Ischemia 9%,
hemorrhage 3%.
o
Recurrence 10-15%
Coiling vs Clipping
o
Factors: aneurysm location, size, shape, neck:dome ratio, luminal thromus,
calcification, collateral supply, parent vessel morphology; patient age, clinical
status, preference; vasospasm
o
o
Raftopoulos (N6/03):
Unruptured. Occlusion rates: Total: CE 56%, SC 93%. Subtotal: CE 15%, SC 2%.
Fail: CE 29% (60% were MCA), SC 5%. Complications: temporary CE 10% SC 16%
permanent CE 8% SC 2%. Recommendation: coil only for DNR >2.5.
o
ISAT (International Subarachnoid
Aneurysm Trial - Lancet 2002):
§
1yr neurologic outcome better with SAH (unruptured
not studied) for CE. 7% risk reduction CE vs SC.
(Only 2 pts from US).
§
Only 20% of eligible patients randomized – most of
rest were clipped. Most centers outside of US. Operator experience not
reported. Patient characteristics atypical (higher H/HI-II, anterior
circulation, <10mm)
o
No difference in shunt-dependent hydrocephalus
between the two groups except with IVH – higher shunt rates with coiling (2
studies, 1 showed higher rates with coiling) (JN 9/04)
o
No difference in Vasospasm (N10/04)
o
Clipping may have a better chance of improving CN3
palsy (N6/06)
·
Specific
aneurysms
o
Cavernous
§
Unruptured may cause ophthalmoplegia (usually without
dilated pupil, cf pcom),
headache, eye pain
§
Ruptured, may cause:
·
SAH, if it expands through carotid ring into subarachnoid space
·