Cerebral Ischemia as an Apparent Complication of Anterior Cervical Discectomy in a Patient with an I

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Cerebral Ischemia as an Apparent Complication of
Anterior Cervical Discectomy in a Patient with an
Incomplete Circle of Willis

• Anes Analg March 2006
• Date 95.6.2
• ???

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Case Report

• 58 y/o male presented for C5-6 ACDF (anterior
  cervical discectomy and fusion) for progressive
  spondylosis with radiculopathy
• No chronic illness, including any form of
  vascular disease
• Tonsillectomy and lumbar laminectomy
• Pre-op ABP 136/80 (99), P 62, R 16
• Induction propofol, fentanyl, SCC
• Maintained with isoflurane, 0.75-1.5 and 50 N2O
  

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Procedure

• An incision made on left side of neck
• Exposure of anterior surface of C5 and C6
  vertebral bodies by Caspar self-retaining
  retractor system under medial border of longus
  colli muscle
• Palpable carotid pulsation
• Temporal pulse was not evaluated
• Accomplished in 1 h and 40 min

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Caspar Cervical Retractor
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Physiologic values during the procedure

• SpO2 99-100
• Heart rate 40-68 bpm (sinus rhythm)
• MAP 48-68 mmHg
• Average MAP 56 mmHg with a pressure nadir of
  75/35 mmHg

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At the conclusion of procedure

• Spontaneous ventilation and extubation
• Not recover full consciousness
• Bilaterally decerebrate with preserved pupillary
  responses and somewhat diminished corneal
  resflexes
• Reintubation

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• Brain CT and MRI performed on the afternoon of
  surgery ? normal
• Echocardiogram, cervical arterial MRA with
  contrast, cervical venous duplex ultrasound of
  jugular veins, CxR, EKG, all lab data ? normal.
• Repeat brain MRI on post-op day 13? diffusely
  increased signal on diffusion weighted imaging

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• The patient improved gradually during 9 wk
• Significant motor aphasia, moderate spastic right
  hemiparesis, impulsivity, significant cognitive
  deficits

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Discussion

• Cerebral ischemia
• ? some retraction-related compression of
• carotid artery
• ? moderate ABP reduction
• ? CW with very little compensatory
• collateral flow

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Carotid compression

• ACD/ACDF? lateral displacement of carotid sheath
  and strap muscles, medial displacement of trachea
  and esophagus
• Tip of retractor blades anchored under medial
  edges of longus colli muscles
• Palpate carotid artery superior to retractor
• Some possibility of false positive confirmation
  of adequate flow

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Study of physiologic effects of pressure on
carotid artery

• Pollard and Little (2002) Duplex sono
• average reduction in carotid cross-sectional area
  of 30 in patients undergoing ACD/ACDF, with
  using Caspar self-retaining retractors
• The greatest reduction of lumen 45, younger
  patients
• Existing stenosis in atherosclerotic vessels?
  complete vessel occlusion

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Ischemic injury related to carotid compression

• Yeh et al (2004)
• extensive ipsilateral hemispheric infarction
  immediately after a 5-hour ACD/F procedure
• no intra-op hypotension, hypoxia or anemia
• extracranial vessels echo no thrombus nor
  atheroma
• Carotid occlusion during surgery
• Poor collateralization of incomplete CW

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• Chozik et al (1994)
• A major hemispheric infarction occurring 3 days
  after anterior corpectomy and fusion
• Angiography revealed a carotid occlusion
• Stasis-related thrombosis associated with
  sustained retraction, delayed embolization rather
  than intra-op ischemia

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Ischemia caused by retraction

• Sloan et al (1986)
• SSEPs in 18 patients undergoing ACD/F
• 3 pts sustained loss of SSEP shortly after
  retractor placement and 2 pts in whom returned
  after release of retractor

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Circle of Willis-1

• 2 alternative pathways for unilateral carotid
  flow reduction
• Anterior communicating artery
• Posterior communicating artery
• The CW is complete in only 42-52 of
  neurologically normal adults
• Alpers et al 52 at autoposy
• Macchi et al 47 of 118 older pts (mean age, 76
  years) in good health under MRA

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Circle of Willis-2

• 25 ? some combination of bilaterally
  hypoplastic or absent PComs and/or P1 segments
• 3-6 ? absent or hypoplastic anterior
  communicating artery or A1 segments
• 7-8 (MRA) ? combinations of anterior and
  posterior CW anomalies in healthy subjects
• CW abnormalities ? more frequently on the left
  side than on the right

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MAP

• Pre-op ABP 136/80 (99) mmHg
• Intra-op MAP 48-68 mmHg (average 56)
• The lower limit of CBF autoregulation 50 mmHg

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Protective Strategies

• Attention to retractor placement
• Postretraction palpation of carotid and temporal
• Avoidance of hypotension
• EEG or SSEP
• Cerebral oximetry or transcranial Doppler
  ultrasonography

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Thanks for your attention!