Question 24

College comments

Syllabus topic/section: 2.1.8 Neurological Intensive Care L1 condition: acute cerebrovascular injury 

Discussion: 

This question invited candidates to discuss decompressive hemicraniectomy following middle cerebral artery infarction. A standard response was expected to cover the key principles, explore relevant controversies with advantages and disadvantages, and summarise current evidence.

Candidates who addressed the major domains outlined in the glossary of terms for a “discuss” question generally performed well. Those who incorporated evidence from individual trials and pooled analyses demonstrated a deeper understanding and scored higher than those who simply listed trial names. Responses that referenced evidence from decompressive craniectomy for traumatic brain injury or mechanical thrombectomy in stroke were not credited, as these were outside the scope of the question.

Answers that included vague statements - such as “decompressive craniectomy would be provided on a case- by-case basis”- without elaborating on the clinical factors guiding such decisions did not score as highly as candidates who gave a rationale for decision making.

Candidates must be careful with language/symbols that can be confused in the heat of the exam; for instance, symbols like “<” and “>” were incorrectly used by some candidates. Similarly, the terms morbidity and mortality were used interchangeably while summarising evidence.

Interpretation

A "Discuss" question with evidence might seem virtually indistinguishable from a "critically evaluate" question, and candidates may spent long hours considering the hidden meaning behind the decision to start this SAQ with this specific exam vocabulary term instead of the other. 

Key principles:

• MCA infarction has high mortality (70%) and morbidity.
• Much of it is due to raised ICP and midline shift
• This could be relieved by decompressive craniectomy

Advantages and disadvantages:

• A mortality improvement is consistently seen in the literature
• For younger patients, an improved functional outcome is also possible
• The association between raised ICP and mortality seems to be genuine
• The procedure appears to be safe even following thrombolysis and while on antiplatelet agents
• The idea has a strong theoretical foundation 

However:

• Highly invasive
• Potentially lifesaving but produces severely disabled survivors
• Complications of the procedure (seizures, hygroma, local wound and CNS infections and bone graft resorption). 
• Slow recovery and long hospital stay

Relevant controversies:

• Unclear diagnostic and therapeutic criteria to identify those who would benefit (eg. on the basis of age or premorbid function)
• Unknown benefits in lower-resourced environments
• The effect of age on outcome is not fully understood
• The timing of the procedure remains debated (within 48 hrs vs later)

A summary of the current evidence:

• Four major studies from ~10-20 yrs ago: DESTINY trial (2007), DECIMAL trial (2007), HAMLET trial (2009), DESTINY II Trial (2014)
• These were very small (pooled analysis of the first three only totalled 93 patients)
• NNT = 2 for mortality, 4 for major disability and mortality combined
• DESTINY-II specifically looked at the older cohort (>60s) and found 38% of the survivors had a MRS outcome score of >3, i.e. over 60% of the survivors were severely disabled, even though the mortality improved from 70% to 33%