Asymmetric optic nerve sheath diameter as an outcome fator following cranioplasty in ‘syndrome of the trephined’ patients

Background: Decompressive craniectomy (DC) is gaining an increasing role in the neurosurgical treatment of intractable intracranial hypertension, but not without complications. A rare complication is the “syndrome of the trephined” (ST). It occurs when the forces of gravity overwhelm intracranial pressures, leading the brain to become sunken. Methods: We followed-up 5 patients submitted to DC and diagnosed with ST. All were submitted to brain MRI to calculate the optic nerve sheath diameter (ONSD). Our goal was to determine the usefulness of asymmetric ONSD as an outcome factor after cranioplasty. Results: Only two patients presented an asymmetric ONSD, being ONSD larger at the site of craniectomy. Surprisingly these patients had a marked neurological improvement after cranioplasty. They became independent a week after and statistically earlier than others. Conclusion: It is presumed that the presence of an asymmetric ONSD in trephined patients is an independent factor of good outcome after cranioplasty.