3 Vascular Neurosurgery

10.1055/b-0039-171765

3 Vascular Neurosurgery

3.1 Aneurysms

3.1.1 Nonruptured Aneurysms (Table 3.1a)

Risk factors for aneurysm formation

History

  • Previous subarachnoid hemorrhage (SAH)

  • Family history a

Habits

  • Smoking b , 1

  • Ethanol

  • Cocaine

Associated pathology

  • Hypertension

  • Endocarditis

  • Polycystic kidney 2

  • Ehlers–Danlos

  • Marfan’s

  • Moyamoya

  • Pseudoxanthoma elasticum

  • Aortic coarctation

  • Arterial venous malformation (AVM)

  • Fibromuscular dysplasia

  • Dissection with pseudoaneurysm

  • Vasculitis

  • Neurofibromatosis 1 (NF1)

  • Glucocorticoid remediable aldosteronism

aTwo first- to third-degree relatives with intracranial aneurysms →8% risk of having unruptured aneurysm.

bSmoking is the most important modifiable risk factor.

Note: 5% of the population harbors an intracranial aneurysm

ISUIA (International Study of Unruptured Intracranial Aneurysms)

3

ISUIA 1 (Retrospective) (Table 3.1b )

Yearly rupture risk for patients with unruptured intracranial aneurysms

Aneurysms size (mm)

Risk of rupture / y

No previous bleed

Previous bleed

0–10

0.05%

0.5%

10–24

< 1%

< 1%

> 24

6%

ISUIA 2 (Prospective)

4 (Table 3.1c )

Five-year rupture risk for patients with unruptured intracranial aneurysms

Aneurysm size (mm)

Location

<7

7–12

13–24

> 24

Cavernous ICA

0%

0%

3%

6.4%

Anterior circulation

0% (1.5% if previous bleed)

2.6%

14.5%

40%

Posterior circulation

2.5% (3.5% if previous bleed)

14.5%

18.4%

50%

90% develop in the anterior circulation

  • Anterior communicating artery (ACom): 30%

  • Posterior communicating artery (PCom): 25%

  • Middle cerebral artery (MCA) bifurcation: 20%

  • Internal carotid artery (ICA) bifurcation: 8%

  • Other locations: 17%

Predictors for outcome

  • Age: strong predictor of surgical outcome

  • Size and location: predict both surgical and endovascular outcomes

3.1.2 Ruptured Aneurysms: Spontaneous Subarachnoid Hemorrhage (Table 3.1d)

Aneurysm size estimation on angiogram 5

ICA diameter = 6 mm

MCA diameter = 4 mm

Note: Fifteen to 20% of SAH patients have negative angiograms → repeat angiogram reveals an abnormality in 1–2%. Eighty to 90% of spontaneous SAH is caused by rupture of cerebral aneurysm.

Imaging sensitivity

CTA

MRA

>5 mm aneurysm

95–100%

85–100%

<5 mm aneurysm

64–83%

56%

Note: SAH is visible on CT in 90% of patients within 24 hours and 60% of patients after 5 days, while xanthochromia may be present for up to 2 weeks BUT may not be present within first 2 hours.

Location of SAH depending on aneurysm

6 (Table 3.1e)

Frequent aneurysms

Cistern

MCA

Sylvian

Ophthalmic

Carotid

PCom

Carotid

ACom

Lamina terminalis

Pericallosal

Callosal

Basilar apex

Interpeduncular

Posteroinferior cerebellar artery (PICA)

Lateral cerebellomedullary

SAH grades (Table 3.1f)

Hunt and Hess 7

Mortality

World Federation of Neurological Surgeons (WFNS) 8

Grade

Glasgow Coma Scale (GCS)

Major focal deficit (aphasia, hemiparesis)

Grade

1

Asymptomatic or mild headache

Slight nuchal rigidity

1%

5%

15

–

1

2

Severe headache

Cranial nerve (CN) deficit

5%

9%

13–14

–

2

3

Lethargy or

Mild focal deficit

19%

20%

+

3

4

Stupor

Dense deficit (hemiparesis)

40%

33%

7–12

±

4

5

Deep coma, moribund

Decerebrate rigidity

77%

77%

3–6

±

5

Note: Grade 0 in both classifications refers to intact aneurysm.

Hunt and Hess classification: Add 1 grade for serious systemic disease (e.g., hypertension, diabetes mellitus, chronic obstructive pulmonary disease) or severe vasospasm on arteriography.

Glasgow outcome scale

9 (Table 3.1g)

Score

Definition

5

Good recovery

4

Moderate disability (disabled but independent)

3

Severe disability (conscious but disabled/dependent)

2

Persistent vegetative state

1

Death

SAH Grades versus Glasgow outcome scale (Table 3.1h)
Rebleed rates (if not treated)

10 (Table 3.1i)

0–24 h

4%

0–2 wk

20%

0–6 mo

50%

> 6 mo

3%

Note: Rebleed mortality is higher than 50%.

Basics for SAH

11 (Table 3.1j)

ABCs

Airway—Breathing—Circulation

Lines

  • Intubation

  • Central line

  • Arterial line

  • Ventriculostomy

Medication

  • Phenytoin

  • Systolic blood pressure (SBP) control (nitroprusside sodium/not long acting)

  • Nimodipine (60 mg/4 h)

  • Gastrointestinal prophylaxis

  • Steroids for meningismus

Note: Xanthochromia 2 hours to 2 weeks after SAH.

3.1.3 Vascular Spasm

Vascular spasm prognosis (Fisher’s grade)

12 (Table 3.1k)

Grade

Blood on CT

Vasospasm risk (%)

1

No blood detected

21%

2

Diffuse or vertical layers < 1 mm thick

25%

3

Localized clot and/or vertical layer > 1 mm

37%

4

Intracerebral or intraventricular clot

31%

Note: Risk factors for clinical vasospasm also include smoking, low cardiac output, volume depletion, early spasm on angiogram, poor clinical grade, fever, hypertension, and sentinel bleed.

CT sensitivity for SAH ↓ at 24 hours.

Vascular spasm prognosis (Modified Fisher’s grading)

13 (Table 3.1l)

Grade

Blood on CT

Vasospasm risk (%)

1

Focal or diffuse thin SAH

24

2

Grade 1 + intraventricular hemorrhage (IVH)

33

3

Focal or diffuse thick SAH

33

4

Grade 3 + IVH

40

Vascular spasm estimation (TCD: Transcranial Doppler)

14 (Table 3.1m)

Spasm

No

Mild/Moderate

Severe

Lindegaard’s ratio (= velocity MCA:ICA)

<3

3–6

>6

Mean MCA velocity (cm/s)

<120

120–200

>200

Note: Lindegaard’s ratio corrects the mean flow velocity for hyperemia (due to decreased blood viscosity from anemia, pressor use, increased cardiac output). TCD detectable changes in spasm may precede clinical symptoms by up to 24 to 48 hours.

Triple-H therapy (Table 3.1n)

Consider ICP Monitoring + Baseline CT

Triple-H therapy

Targets

Medication

Hypervolemia

CVP: 10 cm H2O

Pwedge: 18 mm Hg

Crystalloids

Hemodilution

Hct:30%

Hypertension

SBP: up to 220 mm Hg

Dobutamine (5μg/kg/min)

add phenylephrine (2 μg/kg/min)

Note:

  • Normal central venous pressure (CVP): 5 – 10 cm H2O

  • Normal pulmonary capillary wedge pressure (Pwedge): 6 – 12 mm Hg

3.1.4 Clipping versus Coiling

ISAT (International Subarachnoid Aneurysm Trial)

15 (Table 3.1o)

Primary outcome

Modified Rankin scale 3–6 at 1 year (= death or dependence)

Dependent/Dead at 1 y

Coiling

24%

Clipping

31%

Risk reduction with coiling

Absolute

Total

7%

Depending on age groups

<50 y: 3%

>50 y: 10%

Relative

22%

Treatment proposal

Old patient + posterior circulation

coil

Young patient + anterior circulation

clip

Note: Coiling: lower risk of epilepsy versus higher risk of late rebleeding. Few basilar tip and middle cerebral aneurysms in study.

3.1.5 Aneurysm Surgery: General Recommendations

Aneurysm operative details/pearls

6 , 16 , 17 (Table 3.1p)

Pre-op SAH grading: imaging/tests

  • If spasm on presentation: coil or wait.

  • Study angiogram: for specifics and orientation of the aneurysm morphology.

  • For very large aneurysms: take into consideration mass effect, intramural calcification

    perform CT to evaluate), intraluminal thrombosis, possibly trial balloon occlusion test (assess collateral flow).

Prerequisites for surgery

  • Have emergency suctions .

  • Have blood available.

  • Have etomidate available.

  • Give dexamethasone (10 mg) and mannitol (1 g/kg).

Operative technique

  • Every artery has a safer surface to dissect.

  • Avoid retraction.

  • Ensure early proximal control.

  • Clip first (in case of multiple clipping) the deep, most inaccessible part of neck.

  • When removing temporary clips: remove distal clips first so as not to congest blood in aneurysm—open in situ first to see if it bleeds.

  • At the end always indocyanine green or Doppler.

Surgical options for fusiform aneurysms (Table 3.1q)

  1. Wrapping.

  2. Clip reconstruction.

  3. Trapping (± distal revascularization).

Attention to perforators!

Temporary clipping

18 (Table 3.1r )

Duration of temporary clipping

Further actions

Cooling to 35°C PLUS

<5 min

Nothing

5–10 min

Etomidate:

  • Load (0.5 mg/kg)

  • Rebolus (0.1 mg/Kg)

>10 min

  • Etomidate protocol

  • Remove clip and reperfuse for 10 min

  • Consider circulatory arrest + deep hypothermia

Intraoperative rupture (Table 3.1s)

  • Large rescue suctions.

  • Always have temporary clip preselected.

  • Tell anesthesia.

  • Tamponade (cottonoid—suction).

  • Proximal control.

  • Burst suppression (etomidate).

  • Adenosine-induced circulatory arrest. 19

Five to 10% of aneurysm cases.

Intraoperative papaverine for vessel in spasm (Table 3.1t)

  1. 30-mg papaverine in 9 mL of saline.

  2. Dip cottonoid

  3. Place cottonoid on spasm artery for 2 min.

Paine’s point

20 (Table 3.1u)

  • From sphenoid ridge: 2.5 cm up + 2.5 cm anterior.

  • 4.5-cm deep

3.1.6 Aneurysm Surgery: Details per Location

Proximal ICA (Paraclinoid

a ) aneurysms (Table 3.1v)

Head position/craniotomy

Pterional craniotomy + aggressive drilling of sphenoid wing and orbital roof + possible drilling of anterior clinoid

Proximal control

  1. Carotid in neck with pentothal-induced burst suppression:

    • Also permits retrograde suction–decompression of aneurysm + intra-opangiography

    • Expose cervical ICA in large and ruptured aneurysms

    OR

  2. Balloon microcatheter endovascularly in cervical ICA:

    • Risk of thromboembolism and dissection

Distal control

ICA proximal to PCom

General surgical pearls

  • Retractor blade on posterior aspect orbital cortex

  • First cistern to open is the carotid

  • Clinoid: semilunar flap → turned to protect ICA and aneurysm

  • Dissect CN II prior to clipping (march around)

Aneurysm-specific surgical pearls

  • Ophthalmic (usually dome projects superiorly):

    • Unroofing optic canal (early decompression of optic nerve)—medial clinoid—optic strut (last 5–7mm) → then open falciform ligament

    • Protect the ophthalmic artery

  • Superior hypophyseal (usually dome projects inferomedially): more clinoid but no unroofing optic canal

  • Lateral pointing: aggressive removal clinoid

Notes:

  • Attention to pneumatized clinoid or strut: possible delayed CSF fistula, infection.

  • Intra-op digital subtraction angiography (DSA) is most useful.

aParaclinoid: aneurysms at the origin of the ophthalmic artery, the origin of superior hypophyseal artery, the posterior carotid wall proximal to PCom (decreasing order of frequency).

PCom/anterior choroidal (Ach; supraclinoid) aneurysms (Table 3.1w)

Head position/craniotomy

  • 3. Rotation:

    • 30 degrees (avoid having to pull temporal lobe)

    • 45 degrees (if more exposure of posterior carotid cistern needed, such as in very large aneurysms)

  • 4. Neck hyperextension (maximizes frontal lobe displacement)

  • 5. Pterional craniotomy

Proximal control

  • VERY PROXIMAL: falciform/carotid area (do it early in the subarachnoid exposure opening the proximal sylvian fissure)

  • Open the arachnoid binding the lateral aspect of optic nerve to the carotid artery

  • The removal of anterior clinoid is almost never necessary

Distal control

  • PCom

  • Anterior cerebral artery (ACA)

  • MCA

General surgical pearls

  • First step is to identify the optic nerve → then place frontal lobe retractor on the orbital cortex and progressively advance medially until over posterior aspect of gyrus rectus.

  • Do not pull temporal lobe

  • Most PCom aneurysms are treated by clips applied along the lateral aspect of carotid artery

  • Find PCom lateral and medial (Doppler it) → occlusion can lead to PCA infarct and anterior thalamoperforating lesion)

  • Find and preserve ACh (can be multiple or duplicated) → occlusion can lead to contralateral hemiparesis, hemisensory loss, hemianopsia

  • Beware of CN III when clipping (parasympathetic on surface)

Note: In patients presenting with CNIII palsies, there is no need to dissect the aneurysm sac from the nerve after clipping (the nerve will recover after evacuation of fundus).

ICA bifurcation aneurysms (Table 3.1x)

Head position/craniotomy

Pterional craniotomy

Proximal control

  • ICA (where depends on morphology → distal to ACh if possible)

Distal control

  • A1

  • MCA

  • PCom (depends on position of proximal control clip on ICA)

General surgical pearls

  • Begin with superficial exposure of MCA bifurcation → continue with opening of horizontal segment lateral to medial following the inferior margin of M1

  • Beware of perforators: be careful of small perforating arteries on the posterior aspect of aneurysm

  • Beware of where ACh is (may hide under dome):

    • Do not clip by mistake

    • Always identify the ACh after the placement of clip

  • Know what each A1 feeds and if Acom is patent to know if you can sacrifice ipsilateral A1 with clip during rupture

  • Know the proximity of lenticulostriate arteries to M1 origin

  • Clip along axis M1

ACom aneurysms (Table 3.1y)

Head position/craniotomy

  • Rotation: 50 degrees (so you can see contralateral A1)

  • Side:

    • For symmetric A1 → right-sided approach

    • For asymmetric A1 → side of dominant A1

  • Pterional craniotomy (obtain good frontal exposure)

  • Consider orbitozygomatic approach for aneurysms pointing superiorly and posteriorly

Regarding side, consider: hematoma, aneurysm from lateral aspect A1–A2 junction, multiple aneurysms, previous craniotomy

Proximal control

  • Ipsilateral A1 + contralateral A1

  • Place Gelfoam on contralateral A1 for easy identification during rupture

Distal control

  • Ipsilateral A2 + contralateral A2

  • When removing clip: REMOVE A2 BEFORE A1

General surgical pearls

  • Find Heubner: consider it the most medial of medial lenticulostriates—within 4 mm of ACom in 95% of patients

  • Find A2 in interhemispheric fissure (have in mind orbitofrontal and frontopolar arteries)

  • Know if A2 fills from both A1s in case you must trap. Also evaluate preoperatively if there is a “third” A2.

  • Follow back side of A1 to A2 to avoid marching on dome.

  • Gyrus rectus resection: liberal (improves exposure of ipsilateral A2 and proximal neck—be careful to preserve the orbitofrontal and Heubner arteries)

Notes:

  • The orientation of ACom varies from coronal to truly sagittal.

  • Approaches: interhemispheric (difficulty in proximal control), subfrontal (careful with frontal sinus), transsylvian approach.

  • Consider potential impact of the clip to the optic apparatus and contralateral A1.

MCA aneurysms (Table 3.1z )

Head position/craniotomy

  • Rotation: 30 degrees (so that temporal lobe falls off)

  • Pterional craniotomy

Proximal control

M1

  • Unruptur ed aneurysms: distal to proximal opening of the sylvian fissure (follow initially the outer surface of superior trunk)

  • Ruptured or proximal M1 aneurysms: proximal to distal, beginning from ICA in carotid cistern (early proximal control requires retraction of frontal lobe)

Distal control

M2

General surgical pearls

  • During pre-op planning, evaluate the potential need for revascularization preserving the parietal branch of superficial temporal artery

  • MCA bifurcation is in the most lateral aspect of the sphenoidal segment of sylvian fissure, 2 cm posterior to the anterior extent of the superior temporal gyrus

  • For distal to proximal approach: begin the dissection of the cortical fissure 3–4 cm posterior to the anterior limit of superior temporal gyrus

  • For proximal to distal approach: begin dissection of sphenoidal fissure, 2 cm medial to lateral edge of sphenoid ridge

  • Preserve all perforating vessels of M1 (risk of capsular infarct). Also, be careful of anterotemporal artery (inferior surface M1)

Notes:

  • The most common location is MCA bifurcation → the two M2s exit the bifurcation at 90 degrees from M1 and 180 degrees from each other.

  • The arteries do not cross the sylvian fissure, so they can always be mobilized toward the frontal or temporal lobe versus sylvian veins, which are generally mobilized toward the temporal side.

Pericallosal aneurysms (Table 3.1aa)

Head position/craniotomy

  • Study Sagittal MRI: define the relationship of aneurysm to corpus callosum

  • Unilateral interhemispheric approach anterior to coronal suture

Proximal control

  • Can get there under aneurysm

  • Identify contralateral artery

Distal control

General surgical pearls

  • Make sure the craniotomy exposes at least part of the sagittal sinus

  • Avoid sacrificing veins draining into the sagittal sinus

  • Do not pull on cingulate gyrus. Avoid trauma to both cingulate gyri

  • Lateral retraction < 2.5 cm

  • May take some genu of the corpus callosum to get proximal

Notes:

  • Pericallosal and callosomarginal send branches only to one hemisphere.

  • The falx is thin anteriorly and widens posteriorly.

Basilar tip aneurysm (Table 3.1bb)

Head position/craniotomy

  • Rotation: ~50 degrees rotation

  • Neck: Extend (maxillary eminence above orbital rim; balance between overlapping temporal lobe and overlapping ICA)

  • Craniotomy:

    • Frontotemporal approach (usually right for right-handed parents) is a popular choice + performing additionally orbitozygomatic craniotomy is a possibility

    • Subtemporal approach can also be used

Proximal control

Basilar below superior cerebellar artery (SCA)

Distal control

  • PCom

  • P1

  • SCAs

General surgical pearls

  • Choose left side in case of ipsilateral oculomotor palsy, contralateral hemiparesis, coexistence of other aneurysms

  • Posterior clinoidectomy may be necessary

  • Payne’s point → remove cerebrospinal fluid (CSF)

  • Use the carotid–oculomotor triangle

  • Resect uncus

  • Temporary clip lateral to oculomotor nerve

  • May sacrifice PCom (at P1–P2 junction). Use clips, not coagulation. Never sacrifice a fetal Pcom

  • Must see perforators

Notes: The most common in the posterior circulation. Ninety percent lie within 1 cm of dorsum sellae.

PICA aneurysms (Table 3.1cc)

Head position/craniotomy

  • Position: three-fourths prone

  • Rotation:

    • Neck flexed and rotated (45 degrees)

    • Vertex inclined toward the floor (30 degrees)

  • Skin incision: “hockey sick”

  • Craniotomy:

    • Suboccipital, far lateral approach

    • Adequate exposure of craniocervical junction prior to dural opening (first suboccipital craniectomy → then C1 hemilaminectomy → finally resection of occipital condyle)

Proximal control

Vertebral proximal

Distal control

Vertebral distal (LOOK FOR IT MEDIALLY NOT CEPHALAD). Often difficult

General surgical pearls

POST-OP: assume lower CN issues:

  • Lateral: CN XI

  • Medial: CN XII

  • Superior: CN IX and X

Notes:

  • Cervical PICA origins are not uncommon.

  • Bypass options in case of vessel sacrifice include occipital–PICA or PICA–PICA bypass.

  • Be careful of exposed mastoid air cells.

Vertebrobasilar (VB) junction aneurysms (Table 3.1dd)

Head position/craniotomy

  • As in PICA

  • Lesion at the junction of proximal and middle thirds of clivus

Proximal control

Both vertebrals proximally

Distal control

Basilar

  • Expose between CNs VII/VIII and IX/X/XI

  • Complete or incomplete fenestration may be present

General surgical pearls

  • Know PCom circulation so you can trap both vertebrals if necessary

  • Approach from side of lesion

  • There is no need to perform C1 hemilaminectomy

Note: The most technically demanding.

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May 11, 2020 | Posted by in NEUROSURGERY | Comments Off on 3 Vascular Neurosurgery

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