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7.1\ Anterior Craniofacial

Resection

7.1.1\ Discussion

Anterior cranial (craniofacial) resection is the treatment of choice for aggressive tumors, such as sinonasal undifferentiated carcinoma (SNUC) and esthesioneuroblastoma, that are adjacent to or extend into the anterior cranial fossa. This approach is also sometimes used for resection of suprasellar tumors. The procedure consists of extensive removal of the anterior skull base and nasal cavity and paranasal sinus structures along with tumor resection. This may require both transnasal and anterior skull base (i.e., transbasal, cranio-orbital) approaches. The dura is repaired

D.T. Ginat, M.D., M.S. (*)

Department of Radiology,

University of Chicago, Chicago, IL, USA e-mail: dtg1@uchicago.eduG

P.M. Horowitz, M.D., Ph.D. Department of Surgery,

University of Chicago, Chicago, IL, USA

G. Moonis, M.D.

Department of Radiology, Columbia Presbyterian, New York, NY, USA

S.K. Mukherji, M.D., M.B.A., F.A.C.R.

Department of Radiology, Michigan State University, East Lansing, MI, USA

using dural patch grafts, which may consist of pericranial or fascial autograft, acellular cadaveric dermal allograft, xenograft (bovine pericardium), or synthetic collagen-based matrix. The defect in the floor of the anterior cranial fossa can be closed with vascularized pericranial or nasoseptal rotational flaps, titanium mesh, bone graft, synthetic implant, or a combination of these (Figs. 7.1, 7.2, 7.3, and 7.4). In cases of large defects, free flap reconstruction may be used. Vascularized pericranial flaps, which are created by stripping away the periosteum from the outer table of the calvarium, typically demonstrate enhancement on MRI.

During anterior cranial resection, the frontal lobes may be retracted to some degree, which predisposes to local ischemia at the site of retractor placement. Aggressive retraction, which might be implemented for removal of large tumors, can avulse the lenticulostriate vessels, leading to basal ganglia infarcts (Fig. 7.5).

Infection acquired after anterior cranial resection is predisposed by concurrent partial anterior frontal lobectomy, prior craniotomy, persistent cerebrospinal fluid fistula, and high doses of radiation therapy. Alloplastic materials used for reconstruction and devitalized tissues are also risk factors for postoperative infection, potentially serving as niduses for microorganisms. Wound infections tend to occur along the lateral forehead where the skin incisions are made (Fig. 7.6), while ­intracranial infections are often

in the midline, due to the proximity to the sinonasal passages and potential fistula formation (Fig. 7.7).

Follow-up imaging is important for monitoring tumor recurrence. MRI is the study of choice for postoperative surveillance (Fig. 7.8). Following craniofacial resection, MRI often demonstrates enhancing soft tissue related to granulation tissue formation at the resection site in the superior nasal cavity that is difficult to differentiate from residual or recurrent tumors, such as esthesioneuroblastoma. FDG-PET/CT can also be useful for evaluating for the presence of posttreatment tumor, although infection and inflammation of the resection bed can be hypermetabolic, similar to recurrent tumor.

Radiation therapy is often administered for malignant tumors treated via anterior craniofacial resection. This can result in radiation necrosis, which has a characteristic pattern of white matter signal abnormality and ring-enhancing lesions in the distribution of radiation field and mainly occurs 6 months to 1 year after treatment (Fig. 7.9).

Another important complication of anterior cranial fossa resection is encephalocele, particularly if only a pericranial flap was used to repair the skull base defect. On CT, a postoperative encephalocele appears as nonspecific soft tissue attenuation with variable amounts of surrounding cerebrospinal fluid attenuation. Thus, MRI is useful for making the diagnosis since the continuity of the lesion with the intracranial brain parenchyma can be readily established and differentiated from tumor recurrence or sinus mucosal disease (Fig. 7.11).

Since anterior cranial fossa resection typically involves access through the paranasal sinuses in addition to craniotomies, there is the risk of transgressing the lamina papyracea and orbital entry. This may injure the rectus muscles and other orbital contents (Fig. 7.11). Other complications associated with FESS can also occur with anterior cranial fossa resection. As the normal air flow through the nasal sinuses is frequently disrupted, mucocele formation and chronic inflammatory changes in the paranasal sinuses are common.

Fig. 7.1  Illustration of the anterior cranial fossa approach with skull base reconstruction using pericranial flap and dural patch, titanium mesh, and bone graft

Pericranial flap and dural patch

Titanium mesh Bone graft

Fig. 7.2  Anterior cranial resection with vascularized pericranial flap. Sagittal T2-weighted (a), T1-weighted (b), and post-contrast T1-weighted (c) MR images show

pericranial flap reconstruction of the anterior cranial fossa (arrows). The flap appears as a thin sheet that enhances

Fig. 7.4  Anterior cranial resection with bone graft reconstruction. The patient has a history of a large sinonasal undifferentiated carcinoma (SNUC) involving the anterior skull base treated via anterior craniofacial resection. Preoperative coronal CT image (a) and coronal post-­ contrast T1-weighted (b) MRI show the heterogeneously enhancing paranasal sinus mass extending through the cribriform plate and into the anterior skull base. Postoperative coronal (c) CT image shows extensive para-

nasal sinus and skull base resections. There are no residual ethmoid cells. A split calvarial bone graft harvested from the frontal bone was used to close the skull base defect. Postoperative coronal post-contrast T1-weighted (d) MRI also shows the extensive anterior craniofacial resection. The low-signal-intensity anterior skull base bone graft lies superior to the pericranial flap. There is mucosal thickening, but no evidence of residual or recurrent tumor

a

b

Fig. 7.7  Intraparenchymal abscess with fistula. The patient presented with fever after esthesioneuroblastoma resection. Axial T2 FLAIR (a) and sagittal (b) post­ -­contrast T1-weighted MR images show a large left anterior frontal lobe rim-enhancing cavity containing an air-fluid level. There is extensive signal abnormality surrounding the abscess, which represents cerebritis

Fig. 7.8  Squamous cell carcinoma recurrence after anterior cranial fossa resection. Coronal post-contrast T1-weighted MRI shows a large heterogeneously enhancing craniofacial mass that extends across the craniotomy into the intracranial compartment and right orbit

Fig. 7.9  Radiation necrosis. Axial T2 FLAIR (a) and coronal (b) contrast-enhanced T1-weighted MR images show extensive bifrontal edema and heterogeneous

peripherally enhancing lesions, which are in the distribution of the radiation field after anterior cranial resection

Fig. 7.10  Encephalocele after anterior cranial resection. Coronal T2-weighted MRI demonstrates a large encephalocele (arrow) through the anterior cranial fossa defect

Fig. 7.11  Rectus muscle injury. The patient presented with right restrictive esotropia following anterior cranial resection and radiation treatment of a squamous cell carcinoma. Coronal post-contrast T1-weighted MR image shows enhancing, amorphous soft tissue material in the right posterior ethmoid air cells that represents scar, which retracts the medial rectus muscle (arrow) through a defect in the lamina papyracea