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Intraoperative neuromonitoring and complications

SSEP usage during spine surgery and management of intraoperative durotomy

13 questions 2 source pages 1 fact-check flags

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13 questions
Q1What is the incidence and what are the sequelae of an intraoperative durotomy?▸
  • Incidence 4-17%
  • Pseudomeningocele - postural headache, back pain, neurocompression
  • CSF leak
  • Meningitis
Q2How is an intraoperative durotomy repaired?▸
  • Inform anaesthetist
  • Trendelenberg position to decrease flow
  • 5-0 prolene for watertight repair (continuous running)
  • +/- fat graft / dura patch / fibrin glue / blood patch
  • Subfascial drain with no suction
Q3How is the repair checked and how is the patient managed postoperatively?▸
  • Check with Valsalva to 40mmHg
  • Bed rest 5-7 days - no benefit of prolonged bed rest (ESJ 2020)
  • Prophylactic Rocephin for 5 days
Q4What raises suspicion of a dural tear postoperatively?▸
  • Headache on erect, vomiting, meningism
  • Glucose on multistix in drain fluid
  • Clear fluid in drain or from wound
  • Beta-transferrin in fluid
Q5What is the management of a CSF leak discovered postoperatively?▸
  • Subfascial drain to prevent fistula
  • 3rd generation cephalosporin (crosses BBB)
  • Bed rest 3-5 days, gradual tilt up then mobilisation
  • Observe 3 days; if persistent symptoms/leakage re-explore (Khan 2006 Spine)
  • No long-term sequelae if suspected early
Q6Describe SSEP monitoring in spine surgery.▸
  • Monitors the dorsal column
  • Stimulation: UL ulnar nerve, LL posterior tibial nerve
  • Recording: cortical, subcortical (C5), peripheral (Erb's point UL, popliteal fossa LL)
  • Advantage: not affected by muscle relaxant
  • Disadvantage: unremarkable in anterior cord syndrome
Q7Describe MEP monitoring.▸
  • Monitors the anterior and lateral corticospinal tracts
  • Input: transcranial (motor cortex); output: gastrocnemius, EHL
  • Advantage: detects ischaemic injury (anterior spinal artery)
  • Disadvantage: altered by muscle relaxant
Q8What precautions are needed with intraoperative neuromonitoring?▸
  • Mouth guard so the patient does not bite their tongue
  • Needles - shaving; risk of retained needles
  • Seizures
  • Burns under stimulating electrodes
  • Movement-induced injury
  • Transient arrhythmia
Q9What defines a loss of signal and what should the surgeon do?▸
  • SSEP amplitude reduced >50% or latency increased >10%; MEP reduced >50%; EMG firing
  • Stop current manipulation; release traction
  • Check dura for compression
  • Reverse corrective manoeuvre and rod removal
  • Confirm stability of the spine; look for implant malposition
  • Assess blood loss; warm saline wound wash, less correction
Q10What should anaesthesia and the neurophysiologist do after a loss of signal?▸
  • Check if a bolus of anaesthetic drug or muscle relaxant was given
  • Lighten depth of anaesthesia
  • Increase BP (MAP >90mmHg)
  • Optimise oxygenation, Hb, pH, temperature
  • Neurophysiologist: repeat MEP trials, increase stimulus strength, assess pattern of changes
  • OT technician: reduce noise and electrical interference
Q11If there is no improvement, what are the next steps and what is a Stagnara wake-up test?▸
  • Increase MAP >100mmHg
  • Consider steroid administration
  • Consider wake-up test
  • Consider aborting surgery
  • Stagnara test: test voluntary feet movement; can miss early ischaemia and is not continuous
Q12What other intraoperative neurological monitoring methods are available besides SSEP and MEP?▸
  • Intraoperative NCT
  • Free-running EMG - real-time monitoring of motor nerve root function
  • Neurotonic changes are a sensitive indicator of nerve root injury
  • Stimulus-triggered EMG
Q13What are the potential sources of false negatives and false positives in neuromonitoring?▸
  • False negative: a transected distal part still has electrical activity before Wallerian degeneration
  • False negative: higher stimulation threshold in pre-existing axonal damage; abnormal roots may not evoke neurotonic discharge
  • False negative: screws may enlarge the holes on insertion
  • False positive: electrocautery and irrigation cause interference and artefacts

Fact check

Prophylactic Rocephin (ceftriaxone) for 5 days after intraoperative durotomy — contested; routine prolonged postoperative antibiotics are not evidence-based — Meta-analyses show postoperative prophylactic antibiotics (including courses >24-48h) do not reduce surgical site infection after spine surgery; extended courses are not supported for uncomplicated durotomy repair — (medium confidence) — source
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