Positioning Injuries in Neurosurgery: Anesthesia Perspective

🔹 Introduction

Proper patient positioning in neurosurgery is vital for:

• Optimal surgical access
• Cerebral hemodynamic stability
• Spinal alignment
• Prevention of pressure and stretch injuries

However, these same positions can predispose patients to position-related complications, especially during prolonged surgeries under anesthesia, where the patient cannot communicate discomfort.

Neurosurgical positions are often non-physiological and prolonged, making anesthesiologists crucial in ensuring patient safety.

🔹 Common Neurosurgical Positions

1. Supine
2. Lateral (Park-bench)
3. Prone
4. Sitting
5. Concorde/Modified Prone
6. Three-quarter prone

🔹 Mechanisms of Positioning Injuries

• Compression: Nerves, vessels, soft tissue
• Stretch: Brachial plexus, sciatic nerve
• Ischemia: Pressure points → skin breakdown, rhabdomyolysis
• Obstruction of venous return: ↑ICP, cerebral edema
• Airway compromise: Neck flexion or compression

🔹 Injuries Associated with Common Positions

1. Supine Position

Used in: Supratentorial craniotomy, frontal tumors, burr hole surgeries

✅ Potential Injuries:

• Brachial plexus injury: Excess arm abduction (>90°) or shoulder roll
• Ulnar nerve neuropathy: Elbow compression
• Pressure sores: Sacrum, heels, occiput
• Back pain: Inadequate lumbar support
• Obstructed venous drainage: If neck rotated or flexed

Prevention: Tuck arms neutrally, pad bony prominences, neutral neck

2. Lateral (Park Bench) Position

Used in: Posterior fossa surgeries, acoustic neuroma excision

✅ Potential Injuries:

• Brachial plexus injury: Dependent arm traction/compression
• Peroneal nerve injury: Compression against fibular head
• Eye compression (down eye)
• Axillary artery/vein compression: Inadequate axillary roll
• Neck vessel kinking: Excess rotation

Prevention: Axillary roll, neutral head alignment, padding between knees/arms

3. Prone Position

Used in: Posterior fossa, spine surgeries, Chiari decompression

✅ Potential Injuries:

• Pressure eye injury: Retinal ischemia → post-op blindness
• Facial nerve injury: Compression from headrest
• Abdominal compression: ↓Venous return → ↑bleeding
• Brachial plexus injury: Arm overextension
• Femoral nerve injury: Hip hyperextension
• Pressure ulcers: Knees, chest, iliac crests

Prevention: Horseshoe headrest (not eye area), chest rolls, frequent checks, head neutral

4. Sitting Position

Used in: Posterior fossa, pineal tumor, cervical spine surgeries

✅ Unique Risks:

• Venous Air Embolism (VAE)
• Paradoxical air embolism (PFO)
• Quadriplegia: Cervical spine overflexion → spinal cord compression
• Tongue swelling / macroglossia: Venous congestion
• Mid-cervical flexion myelopathy
• Sciatic nerve injury: Stretch due to hip flexion

Prevention: TEE or precordial Doppler for VAE, PFO screening, neutral neck, pressure point care

5. Concorde/Modified Prone

Used in: Midline posterior fossa, cerebellar surgeries

✅ Injuries:

• Similar to prone
• Cervical strain: Due to downward head flexion
• Tongue swelling and airway edema post-op

🔹 Specific Nerve Injury Table

🔹 Eye Injuries in Neurosurgery

🛑 One of the most feared complications of prone neurosurgery is Perioperative Visual Loss (POVL)

🔸 Mechanisms:

• Ischemic optic neuropathy (ION)
• Retinal artery occlusion
• Direct globe compression

🔸 Risk Factors:

• Long duration (>6 hr)
• Significant blood loss
• Prone position
• Anemia, hypotension
• Inadequate eye protection

🔸 Prevention:

• Avoid direct eye pressure
• Maintain hemodynamics
• Periodic eye checks
• Consider elevating head in prone

🔹 Airway Concerns from Positioning

• Neck flexion → endotracheal tube migration or kinking
• Macroglossia post-op → especially in sitting or Concorde positions
• Cervical spine injury exacerbation → especially in trauma or Chiari malformation

🔹 Anesthesia Role in Preventing Positioning Injuries

• Participate actively during positioning
• Final check of pressure points, lines, head position before draping
• Use of positioning checklists
• Document all positioning aids used
• Communicate with surgeons continuously during long surgeries
• Assess and document limb function post-op (esp. in awake craniotomies)

🔹 Monitoring Tools

• Somatosensory evoked potentials (SSEP): To detect nerve injury intraoperatively
• Peripheral Nerve Stimulator: Can be used to assess neuromuscular integrity
• Intraoperative eye checks: To prevent POVL
• Motor evoked potentials (MEP): Useful in prone spine surgery

📝 Viva Questions

Q: What is the most feared complication of prone neurosurgery?
A: Postoperative visual loss due to ischemic optic neuropathy.

Q: How can you prevent brachial plexus injury in lateral position?
A: Avoid over-abduction of arms, use axillary roll, and support dependent arm.

Q: Which nerve is most at risk in lithotomy or lateral position?
A: Common peroneal nerve.

🔍 References

1. Miller’s Anesthesia, 9th ed., Chapter on Patient Positioning
2. Cottrell and Young’s Neuroanesthesia, 5th ed.
3. StatPearls: Positioning Injuries in Anesthesia
4. BJA Education: Perioperative Positioning and Nerve Injuries
5. WFSA Resources: Safe Positioning in Neurosurgical Patients