Question 25

College answer

Introduction 
 
The main role of DC in TBI is reduction of ICP and prevention of herniation, aggravated by haematoma and brain swelling. Use of this technique is controversial and its efficacy in TBI is uncertain despite recent trials. Two main techniques widely used for DC in TBI are unilateral frontotemporoparietal  craniectomy and bifrontal craniectomy                                                                                          

Rationale 
 
In a decompressive craniectomy, a substantial portion of the skull is removed in order to reduce increased ICP. This can be done in combination with an evacuation procedure or as a primary treatment for increased ICP. The rationale of DC is based in the Monro-Kellie Doctrine. The skull is a rigid unexpandable structure, opening the cranial vault by DC increases the volume available to the intracranial contents and reduces ICP. Current Brain Trauma Foundation guidelines suggested the ICP lower than 20 mmHg after TBI. Patients with well-controlled ICP under the threshold appear to have improved outcomes.                                                                                  

Evidence
DECRA 
 
Published by Cooper et al. in 2011- 155 patients with TBI and either GCS score lower than 8 or CT demonstrating moderate diffuse brain injury were enrolled. Patients with refractory ICP (ICP>20 mmHg for 15 minutes) within a 1-hour period were randomized to one of two groups.  
DC decreased ICP and the length of stay in the intensive care unit but was associated with more patients with unfavourable neurological outcomes. 
Criticisms of DECRA:  
Higher ICP threshold should be used before performing DC in TBI.  
The period of medical management with high ICP was too short prior to randomisation.  
More patients who had non-reactive pupil were enrolled in the DC group (27%) only 12% in medical therapy group.  
The choice of surgical method- only bifrontal DC without falx sectioning allowed. 
No standardised rehabilitation
Long enrolment period  
Less emphasis on CPP.                                                                                  
 

RESCUEicp 
Multicentre (48 centre, 19 countries) RCT 
408 patients (age, 10-65 years) with TBI and refractory elevated ICP (>25 mmHg) were randomized to undergo DC or receive ongoing medical care.  
The primary outcome was the Extended Glasgow Outcome Scale (GOS-E) at 6 months.  
At 6 months patients in DC group resulted in lower mortality and higher rates of vegetative state, lower severe disability and upper severe disability than ongoing medical care group.  The rates of moderate disability and good recovery were similar in the two groups.  
Limitations 
A relatively large proportion of patients in the medical group underwent DC 
 
Pros 
•    Reduces ICP 
•    Increases survival 
•    Decreases ICU length of stay 
 
Cons 
ICP reduction may not necessarily result in better clinical outcomes

Potentially increased numbers of severely debilitated survivors

Surgical complications potentially include: 
•    Axonal stretch 
•    Aggravated brain oedema 
•    Haematoma expansion or bleeding 
•    Infection 
•    CSF leakage 
•    Syndrome of the trephined 
                                                 
Own practice 
We utilise decompressive craniectomy in our unit in young patients with TBI, refractory intracranial hypertension and relatively early in their course prior to irreversible secondary injury 
Clinicians and family members will need to be aware of the risks when potentially employing this strategy. 
Probably useful if mass lesion (excluded in DECRA) 
 
Summary 
There is a growing body of literature with conflicting results. 
Decompressive craniectomy decreases ICP and leads to improved survival. The quality of that survival is the issue, so careful procedure selection, patient population selection and overall situation appreciation are important 
 
The level of detail of the studies given in the template was not required. 
 
Examiners Comments: 
 
Most candidates answered the question as asked, but several wasted efforts explaining other methods of controlling ICP or describing DC use in non-TBI situations. Candidates are reminded to read the stem carefully. 

Discussion

This SAQ is entirely unlike Question 9 from the first paper of 2009, where the focus was more on indications complications and outcomes. This one required some additional depth of analysis, of which probably the most sophisticated area involved the interpretation and presentation of the results of two major trials in TBI management. In spite of the dyssynchronous-sounding "wasted efforts" mentioned by the college, clearly many of the trainees (at least 67.2% of them) have at least a workmanlike knowledge of these issues.

Rationale

• Raised intracranial pressure contributes to secondary brain injury and morbidity/mortality from TBI
• Intracranial pressure is governed by the Monro-Kellie Doctrine, where intracranial content is confined within a finite space and any expansion of one component produces increased pressure on other components
• Decompressive craniectomy increases the volume available to the intracranial contents
• The consequence should be decreased ICP and decreased secondary brain injury.

Evidence

• The DECRA trial:
  • (n=155)
  • No strong evidence for any mortality benefit (19% vs 18%).
  • Worse functional outcomes in survivors
  • However: methodologically flawed:
    • Protocol resorted to surgery too early
    • Patients with "mass lesions" were excluded
    • The bifrontal procedure is suboptimal for controlling ICP (but anyway the ICP control was very good in the decompression group)
    • The 155 patients for this trial took 8 years to enrol
    • Prior to the randomisation, both groups had relatively normal-ish ICPs (upper limit of normal, approaching 20 mmHg). 
• The RESCUEicp trial:
  • n= 408 patients
  • Higher threshold (sustained ICP of > 25mmHg, and sustained for longer, in spite of a good trial of Stage 2 therapies).
  • Improved mortality (26.9% vs 48.9%)
  • More survivors with severe disability
  • Problems with methodology:
    • Of the patients randomised to medical management, 37% underwent decompressive craniectomy anyway. 
    • As with DECRA, recruitment of all 408 patients took 10 years. Half the centres recruited only 3 patients, or fewer.
    • Therapeutic hypothermia was one of the optional Stage 2 rescue therapies prior to reaching for the bone saw, which - we now realise- may confer a survival disadvantage.

Society guidelines

• new (2016) BTF Guidelines:
  • Not recommended to improve outcomes
  • Do a large bifrontal decompression (no less than 12 × 15 cm)
  • (these do not incorporate RESCUEicp results)

Advantages of decompression in TBI include

• Maybe some sort of mortality benefit (cohort studies such as Sonuca et al, 2010; as well as RESCUIicp)
• Shorter ICU stay
• Less ICP-targeting interventions
• Lower ICP

Disadvantages include:

• Conflicting evidence for mortality benefit (19% vs 18% in the DECRA trial, versus 26.9% vs 48.9% in RESCUIicp)
• Worse neurological outcome in survivors
• Multiple complications associated with decompressive craniectomy:
  • Herniation through the defect
  • Delayed paradoxical herniation
  • Subdural hygroma
  • Infection
  • Bleeding
  • Post-traumatic hydrocephalus
  • "Sinking Flap Syndrome"
  • Bone resorption

Own practice

 This section should probably be written delicately. Among the examiners, there is clearly substantial heterogeneity of beliefs regarding this intervention. The "own practice" answer should be sufficiently conservative to please the haters of decompressive craniectomy, while acknowledging that it is difficult to present improved survival as a bad thing. Thus, something like:

• My practice is to reserve decompressive craniectomy for carefully selected patients, who:
  • have severe traumatic brain injury, with or without mass lesions
  • have refractory ICP, difficult to control with Stage 1 and Stage 2 interventions (posture, sedation, paralysis, osmotherapy, cooling)
  • are early in the course of TBI evolution (i.e. do not have well-established structural brain damage)
• My practice would be to discuss the options (decompressive craniectomy, thiopentone coma, conservative management) with the family, taking into account their values and expectations.