Neurosurgery notes/Trauma/Trauma complications/Syndrome of trephine/Cranioplasty

Cranioplasty

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Syndrome of trephine

General

  • Every effort should be made to perform a CP after DC in the absence of medical contraindications and following consent.

Definition

  • Surgical reconstruction of a bone defect after a previous operation, usually DC, or due to skull injury

Indication

  • Anatomical reconstruction (CSF barrier, bone, and soft tissue)
    • Protection of the underlying brain that is left vulnerable to damage with a skull defect
  • Physiological restoration
    • Syndrome of trephine
  • Promote functional and psychological recovery.
    • Restoring the skull contour that might have psychological and social consequences for the patient

Complications

  • (Kurland 2016) -overall complication rate 6.4 %
      • New ipsilateral hematoma
      5.4%
      Meningitis/ventriculitis
      4.5%
      Deep complications in total (meningitis, ventriculitis, cerebral abscess, extradural/subdural empyema)
      4.8%
      Hydrocephalus
      6.2%
      CSF leak
      6.8%
      Superficial complications (wound necrosis/poor healing, wound infection, subgaleal infection)
      5.4%
      Subdural hygroma
      6.5%
      Bone flap/prosthesis infection
      5.4%
      Aseptic bone flap reabsorption
      13.5% Adults
      39.2% Children
      Bone flap depression/cosmetic defect
      3.1%
  • (Malcolm 2016) -overall complication rate 19.5%
      • Complication
      Frequency (%)
      Infection
      8.1
      Reoperation
      12.9
      Intracranial haemorrhage
      4.6
      Extra-axial fluid collection
      6.1
      Hydrocephalus
      6
      Seizures
      6.1
      Bone resorption
      10.8

Graft materials

  • Use of 3D planning techniques, when available, may aid the surgical procedure
  • Analysis of the advantages and disadvantages of common cranioplasty materials
      • Material
      Advantages
      Disadvantages
      Autologous bone
      Accepted by host, low rate of fracture
      Bone resorption, infection
      MMA
      Strong, heat resistant, inert, low cost, ease of use
      Infection, fracture, exothermic burn reaction, inflammation, lack of incorporation
      Hydroxyapatite
      Noninflammatory, decent chemical bonding to bone, excellent cosmesis and contouring ability
      Low tensile strength, brittle, infection, fragmentation, lack of osteointegration
      Titanium mesh
      Noninflammatory, noncorrosive, strong, malleability, low infection rate, good cosmesis
      Expensive, image artifact on imaging
      Alumina ceramics
      Hard, chemically stable, tissue compatible, low infection rate
      Expensive, prone to shatter
      PEEK implant
      Radiolucent, chemically inert, strong, elastic, does not create artifacts on imaging, comfortable, does not conduct temperature
      Cost, need for additional 3D planning and imaging, difficult to bond to other materials, infection

Autologous bone

  • Advantage
    • Low cost
    • Ideal contour
    • Biocompatible
    • Strong
    • Radiolucent
  • Disadvantage
    • Bone resorption
      • Honeybul 2017 RCT of autologous vs titanium cranioplasty
        • 22% had complete bone resorption
      • Risk factor for bone flap reabsorption
        • Younger age,
        • Shunt dependency,
        • Bone flap fragmentation
      • If present causes higher risk of failure and infection
    • Custom-made implants may have better cosmetic outcomes
  • Storage for bone
    • Corliss et al. 2016 found no statistically significant differences in terms of infection, resorption, and/or reoperation rate comparing extra-corporal cryopreservation versus abdominal pocket storage

PEEK

  • Advantage
    • Radiolucent
    • Chemically inert
    • Strong
    • Elastic
    • Does not create artifacts on imaging,
    • Comfortable
    • Does not conduct temperature
  • Disadvantage
    • Cost
    • Need for additional 3D planning and imaging,
    • Difficult to bond to other materials,
    • Infection

Metal

  • Titanium
    • Remains a widely used
    • Advantage
      • Relatively cheap option
    • Disadvantage
      • Artefact on imaging.
    • Lindner 2017: RCT of hydroxyapatite versus titanium
      • Reoperation rate at 6-months (26.9% vs. 29.2% respectively) was similar,
      • Lower number of infections for hydroxyapatite (7.7% vs. 20.8%)
      • Higher number of epidural haematomas for hydroxyapatite (34.6% vs. 8.3%).

Synthetic

  • Acrylic cranioplasty (polymethylmethacrylate, PMMA)
    • Advantage
      • Cheap
      • Malleable
      • Lightweight
    • Disadvantage
      • Fragility of the plates → fractures
      • Exothermic reaction
      • Infection
  • Hydroxyapatite
    • Popular in recent years
    • Advantage
      • Good osseointegration.
    • Disadvantage
      • Cost remains high
      • Material can fracture following trauma.

Timing of reconstruction

  • Controversial
    • Lack of consensus and good quality evidence
    • Early cranioplasty
      • Whether early cranioplasty increases the risk of infections or not is not clear
      • Malcolm 2018 Systematic review (all retrospective), 528 patients, cranioplasty may improve neurological outcome, and earlier (<90 days) cranioplasty may enhance this effect
  • Should take into account
    • The timing of CP should also take into account the state of the skin flap:
      • Depressed skin flap, due to post-traumatic brain atrophy or over-drainage of CSF related to VP shunting;
      • Skin flap is at the same level as the margins of the cranial vault;
      • Skin flap is bulging beyond the cranial vault margin due to brain swelling and/or HC/ventriculomegaly (VM).
      • Wound status
      • Systemic infection
      • Systemic instability
      • Antithrombotic medications
    • Poor neurological status is not a contraindication for cranioplasty per se.
    • Consider expediting the cranioplasty in a patient with neurological and/or neuropsychological deterioration that cannot be attributed to extracranial causes
    • If autologous bone is store subcutaneously consider doing cranioplasty early as it can undergo reabsorption
    • Skin colonization (i.e. carrier) of the patient is not a contraindication for cranioplasty but consideration to decolonization pre-operatively should be given.
  • 1– 12 months
  • Timing definition
    • Ultra-early cranioplasty is up to 6 weeks following craniectomy,
    • Early cranioplasty is 6 weeks to 3 months,
    • Intermediate 3-6 months,
    • Delayed more than 6 months
  • Some fullness of the flap is not per se a contraindication to CP

Technique

  • Careful dissection of the scalp from the dura
  • Closure of any dural tears
  • Exposure of bone margins circumferentially
  • Secure fixation of the autologous bone or artificial implant
  • In cases of an infection,
    • The plate is usually removed and the wound debrided;
    • It is important to wait until the underlying infection is clear
      • A process which can take up to 1 year, prior to re- inserting a plate in order to minimize the risk of further implant infection.
  • Perioperative (temporary) CSF diversion may be considered to aid CP.
  • Artificial implants and bone flaps with a gap to the surrounding skull should be secured.
  • HCP associated
    • In those patients that there is a bulging skin flap, the usage of a temporary external ventricular drain (EVD), or a lumbar drain (LD) may facilitate the cranioplasty.
    • The performance of serial spinal taps, although is not supported by enough evidence, is an option to facilitate the cranioplasty.
    • After the performance of cranioplasty, the patient should be closely followed for signs of HC. In case of persisting or developing HC, CSF diversion needs to be considered.