Syndrome of the Trephined: Clinical Features, Diagnosis, and Management
Syndrome of the trephined (SoT) is a neurological complication following craniectomy characterized by neurological deterioration that improves with cranioplasty, occurring in approximately 24-65% of patients with large skull defects. 1, 2
Definition and Pathophysiology
Syndrome of the trephined, also known as "sinking skin flap syndrome" or "motor trephine syndrome," occurs after decompressive craniectomy when the absence of the skull bone allows atmospheric pressure to compress brain tissue, leading to:
- Altered cerebrospinal fluid dynamics
- Impaired cerebral blood flow
- Shifting of brain structures
- Sunken appearance of the skin flap over the defect
Clinical Presentation
Common Symptoms
- Motor deficits (52-57%)
- Cognitive impairments (41%)
- Language/speech deficits (16-28%)
- Decreased wakefulness (30%)
- Mood disorders (depression/anxiety) (21%)
- Headaches (16%)
- Rehabilitation arrest (more common than acute decline) 3
Timing
- Typically presents 4.4-5.1 months after craniectomy 1, 4
- May occur earlier if CSF diversion procedures (like VP shunts) are performed 5
Risk Factors
- Traumatic brain injury as primary indication for craniectomy (OR: 8.2) 4
- Hemorrhagic lesions 2
- Large craniectomy defects (average 88.3 cm²) 1
- Shifting of brain structures 2
- CSF diversion procedures (VP shunts) 5
Diagnosis
Clinical Evaluation
- Neurological examination showing deterioration or plateau in recovery
- Chronic rehabilitation arrest pattern is more common than acute decline 3
Radiographic Features
- Sunken skin flap contour (most sensitive finding) 3
- Ventricular effacement (most specific finding) 3
- Midline shift
- Evidence of brain tissue compression under the defect
Management
Prevention
- Avoid lumbar drainage in patients with craniectomy defects due to high risk of paradoxical herniation 6
- If CSF drainage is necessary, use external ventricular drainage (EVD) with careful monitoring 6
Definitive Treatment
- Early cranioplasty is the definitive treatment and should be performed as soon as the patient is medically stable rather than waiting the traditional 1-2 years 5, 2
- Earlier cranioplasty is associated with improved neurological recovery (OR: 0.96 per day of delay; 95% CI, 0.93-0.99) 2
Cranioplasty Considerations
- Materials include:
- Polyetheretherketone (PEEK) (48%)
- Titanium mesh (21%)
- Autologous bone (30%) 4
- No significant difference in time to neurological improvement between autologous versus alloplastic materials 4
- Avoid early cranioplasty within 10 weeks due to higher complication rates 6
Post-Cranioplasty Management
- Neurological improvement typically occurs within 3.8 days after cranioplasty 1
- Functional independence with activities of daily living is achieved by approximately 55% of patients after 2.9 months of rehabilitation 1
- Monitor for complications including infection and hematoma
Special Considerations
Management of Paradoxical Herniation
If paradoxical herniation occurs:
- Position patient in Trendelenburg position
- Administer rapid intravenous fluids
- Clamp any CSF drainage catheters
- Consider urgent cranioplasty 6
CSF Management
- Avoid lumbar drainage in patients with craniectomy defects 6
- If CSF diversion is necessary, use EVD with careful monitoring of intracranial pressure 6
- Maintain patient in flat or slight Trendelenburg position if CSF drainage is performed 6
Prognosis
- Approximately 55% of patients achieve functional independence after cranioplasty and rehabilitation 1
- Early cranioplasty is associated with better neurological outcomes 2
- Improvement in neurological function can be dramatic and immediate following cranioplasty 5
SoT is an underrecognized but potentially reversible complication of craniectomy that requires high clinical suspicion, especially in patients who fail to progress neurologically or demonstrate a sunken skin flap.