2026 Poster Presentations
P172: PERI-ROLANDIC INTRADIPLOIC ENCEPHALOCELE WITH BIPHASIC TABLE DESTRUCTION IN AN ADULT: ILLUSTRATIVE CASE OF SURGICAL MANAGEMENT
Umika S Paul, BSE1; Rrita Daci, MD2; Brittany Owusu-Adjei, MD2; Constance J Mietus, MD, PhD2; Mark D Johnson, MD, PhD2; 1Department of Neurological Surgery, University of Massachusetts Chan Medical School; 2Department of Neurological Surgery, University of Massachusetts Chan Medical School, UMass Memorial Health
Introduction: An intradiploic encephalocele is a rare condition in which brain parenchyma herniates into the diploic space through a defect in the inner calvarial table, typically with an intact though thinned outer table. These lesions can mimic lytic skull processes on imaging and are often overlooked. We describe the presentation and management of an unusual case of an adult parietal intradiploic encephalocele overlying eloquent cortex and involving destruction of both calvarial tables.
Case Presentation: A 63-year-old man with a known intradiploic encephalocele presented with new progressive left upper extremity cramping and shaking, concerning for focal motor seizures. At the time of diagnosis, a non-contrast head CT had demonstrated a 5-mm inner table defect with thinning and destruction of the outer table and minimal herniation of brain parenchyma (Figure 1).
MRI (obtained 7 years after initial studies) showed a 6-mm focal dehiscence of the inner table with a 7x12-mm diploic encephalocele overlying the peri-Rolandic region, consistent with interval enlargement (Figure 2).
The patient developed worsening seizures and operative repair was performed. A circumferential craniectomy surrounding the defect exposed thinned, discolored bone cortex consistent with chronic remodeling (Figure 3A). Both outer and inner cortices were removed to healthy margins, revealing intact arachnoid (Figure 3B). Because the herniated brain was presumed functional motor cortex, no parenchymal resection was undertaken. Reconstruction included duraplasty using acellular dermal matrix (AlloDerm) and cranioplasty with low-profile titanium mesh (Figure 3C).
Postoperative imaging confirmed resolution of herniation with stable reconstruction (Figure 4). The patient recovered without new neurological deficits.
Discussion: Intradiploic encephaloceles are rare, with only 23 cases reported in the literature. They most often involve inner table destruction with preservation of the outer table, resembling benign lytic lesions. The present case is unusual given destruction of both inner and outer skull tables, parietal location, and direct abutment of eloquent motor cortex. This atypical morphology raises the possibility of a variant congenital origin or long-standing remodeling, although the clinical course resembled an acquired lesion. These features expand the known spectrum of disease and highlight the importance of including intradiploic encephalocele in the differential of atypical calvarial lesions. Accurate diagnosis depends on recognizing imaging features that demonstrate continuity of brain parenchyma into the diploic space and distinguishing this entity from mimics such as Langerhans cell histiocytosis, epidermoid or dermoid cysts, and arachnoid cyst variants. Management depends on symptoms, growth, and neuroanatomic context. In lesions abutting eloquent cortex, the guiding principle is preservation of functional brain with careful reconstruction rather than parenchymal excision. Reconstruction aims to reconstitute a watertight dural barrier and stable cranial contour, reduce further herniation, and mitigate seizure focus.
Conclusions: This case illustrates a rare parietal intradiploic encephalocele with destruction of both calvarial tables. When MRI demonstrates herniated brain with an associated dural defect, intradiploic encephalocele should be strongly considered. Symptomatic or enlarging lesions typically require surgical management. Recognition of characteristic imaging features and adoption of a cortex-sparing reconstructive approach can achieve symptom control with stable reconstruction while avoiding functional compromise.