1235 - A Rare Case of Sunken Flap Syndrome Post Cranioplasty

Friday, February 20, 2026

5:00 PM - 6:30 PM AST

Presenting Author(s)

AM

Angela Marinovic, n/a

Medical student
McGovern Medical School
HOUSTON, Texas, United States

Co-Author(s)

AR

Alexa Ryder, MD

Resident
McGovern Medical School
Houston, Texas, United States
KV

Kristin Varacalli, DO

Assistant Professor
University of Texas Houston Health Sciences
Houston, Texas, United States

Submitter(s)

AM

Angela Marinovic, MD

McGovern Medical School
HOUSTON, Texas, United States

Case Diagnosis: Sunken Flap Like Syndrome (SFS) Post-Cranioplasty

Case Description: 63-year-old female with a history of right-sided subdural hematoma underwent PEEK cranioplasty in October 2024 after decompressive craniectomy. In December, she was readmitted for infected and exposed hardware. Cultures grew Staphylococcus epidermidis, treated with antibiotics. In January 2025, she returned with weakness and midline shift, requiring repeat cranioplasty. The patient’s neurological status remained stable despite a fluid pocket forming post-op and she was admitted to inpatient rehabilitation. In February, her therapy team noted yellow drainage on the pillow. CT head showed replacement of the prior fluid collection with air, a worsening midline shift up to 1.5 cm, and signs of right uncal herniation. A scalp defect was present at the site. No neurologic changes noted, and neurosurgery was contacted. Conservative management with flat positioning and a non-rebreather mask was initiated. She was transferred back to surgery where she underwent wound revision and epidural-to-peritoneal shunt placement.

Discussions: SFS is a rare complication of decompressive craniectomy, where external atmospheric pressure causes the skin and soft tissue to sink inward at the craniectomy site, disrupting intracranial pressure and cerebrospinal fluid (CSF) dynamics. The typical treatment is cranioplasty with replacement of the bone flap. However, SFS can still develop post-cranioplasty due to complications like VP shunt malfunction, infection, or reperfusion injury. SFS from a ruptured cyst is uncommon. In this case, negative intracranial pressure from air entry after cyst rupture promoted dural collapse and herniation.

Conclusions: This case highlights a rare etiology of SFS with negative intracranial pressure caused by air entry after cyst rupture. Unlike typical SFS caused by external atmospheric pressure, this demonstrates a vacuum-like effect promoting dural collapse and herniation. Providers must remain alert for delayed decline after cranioplasty, especially in patients with prior infection or subgaleal collections. Timely imaging and intervention are essential for optimal outcomes.