4.20.8\ Textiloma

Resorbable and nonresorbable hemostatic agents can incite foreign body reactions that appear masslike and can mimic neoplasm or abscess. Various terms are used to describe this granulomatous reaction, such as textilomas, gossypibomas, gauzomas, surgicelomas, and muslinomas. While

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each agent exhibits distinctive morphologic features that often permit specific identification, these typically consist of a core of degenerating hemostatic agent surrounded by an inflammatory reaction, which can demonstrate enhancement on imaging (Fig. 4.64). The presence of hemostatic material at the site of the lesion on baseline imaging, if available, can be a helpful clue.

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Fig. 4.64  Textiloma. Initial postoperative CT image (a) shows the hemostatic agent along the left planum sphenoidale (arrow). Follow-up axialT2-weighted (b),T1-weighted

(c), and post-contrast T1-weighted (d) MR images show a well-defined lesion with peripheral enhancement (arrows)

4.20.9\ Sunken Skin Flap Syndrome

Sunken skin flap syndrome (syndrome of the trephined) is an uncommon, late complication of craniectomy, usually occurring 1 month after surgery. This complication consists of depression of the scalp flap and brain deformity at the site of craniectomy (Fig. 4.65). The cause is presumed to be atmospheric pressure that exceeds intracranial

pressure. Large craniectomy defects predispose to the development of sunken skin flap syndrome, and brain atrophy accentuates the degree of concavity. This condition is certainly not cosmetically pleasing and may even compromise cerebral blood flow. Furthermore, along with headache, fatigue, and seizure, sunken skin flaps may be a manifestation of trephine syndrome. These outcomes often improve following cranioplasty.

4.20.10  External Brain Herniation

Following craniectomy for cerebral edema, extracranial herniation of the brain occurs in over 25% of cases. Although some degree of brain expansion is expected after craniectomy, extension of brain tissue beyond 1.5 cm measured at the center of the osseous defect with respect to the outer table of the calvarium is generally considered abnormal. Extracranial cerebral herniation is more likely to occur with small craniectomy defects. This can produce a characteristic “mushroom cap” appearance of the deformed brain tissue (Fig. 4.66). The herniated brain tissue is particularly susceptible to trauma. Extracranial herniation can also lead to venous infarcts secondary to cortical vein compression. This risk of substantial external brain herniation is lower with larger craniectomies.

Fig. 4.66  External brain herniation. Axial CT shows substantial herniation of the intracranial contents through the left craniectomy defect with a “mushroom cap” appearance posteriorly

4.20.11  Bone Flap Resorption

Although mild remodeling of the bone flap edges over time is expected and of no consequence, severe bone flap resorption can be problematic. This is a delayed complication that occurs in 6–12% of cases. As resorption progresses, the bone flap becomes detached from the securing

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plates, and sunken scalp syndrome may ensue. Alternatively, intracranial contents can herniate through the defects. On CT, bone flap resorption appears as tapered edges and wide gaps between the calvarium (Fig. 4.67). These patients can benefit from artificial cranioplasty, and high-resolu- tion 3D CT is particularly helpful for surgical planning subsequent repair.

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Fig. 4.67  Bone flap resorption. Coronal CT (a) and 3D CT (b) images demonstrate thinning of the right frontal bone flap edges with wide gaps between the craniotomy

flap and the rest of the calvarium. Consequently, some of the cranial plates are not fully anchored to bone