IMAGING PATTERNS OF SKULL BASE ENCEPHALOCELES WITH CTMR

IMAGING PATTERNS OF SKULL BASE ENCEPHALOCELES WITH CT/MR FUSION Mina L. Labib, M. D. Bradley N. Delman, M. D. Icahn School of Medicine at Mount Sinai New York, NY 10029 Session ID: 2354 session ID: e. P-2 Control #: 2739 Sub Poster #: e. P-133

DISCLOSURES • M. L. Labib, M. D. • No disclosures • B. N. Delman, M. D. • Bayer Healthcare • Consultancy • Advisory Board

PURPOSE

SKULL-BASED DEFECTS • Skull-based defects are frequently encountered in the hospital setting. • These may develop as the result of • Trauma • Skull base surgery • Infections • Tumors • Congenital deformities. • Spontaneous development, especially in setting of idiopathic intracranial hypertension (IIH) or impaired CSF drainage

MANIFESTATION • These skull-based defects can manifest as: • Encephaloceles • Meningoencephaloceles • Cerebrospinal fluid (CSF) leak

CLINICAL IMPORTANCE • Complications of skull-based defects • A persistent CSF leak can lead to headache of varying, sometimes debilitating, intensity. • CSF leaks are associated with an increased risk of meningitis. • Skull-based defects that may become symptomatic or predispose to meningitis should be promptly diagnosed and corrected. • Determining the precise location of these defects is essential for surgical correction. • Understanding pattern and typical appearance of skull-based defects is of great import to the neuroradiology community

MATERIALS AND METHODS

MATERIALS AND METHODS • A retrospective review of patients evaluated for skull base CSF leaks at our institution over the past 6 years was performed. • Patients were evaluated with either • Routine MRI • MR/CT fusion

MOUNT SINAI MR/CT FUSION PROTOCOL • • CT Sinuses • Non-contrast Helical acquisition • Minimum collimation: 0. 625 mm with recon overlapof 30% • Coverage: Paranasal sinuses and mastoids through the vertex MRI Sinuses • With and without contrast • 3 Tesla magnet • Extended echo train T 2 coronal at beginning of scan (early) • Extended echo train T 2 coronal at conclusion of scan (after ~45 min) THEN • Fusion on GE AW Server • 3 Series are typically returned to PACS for analysis: • Fused CT/MR (T 2 MR in color over grayscale CT) • Pure CT as grayscale • Pure T 2 MR as grayscale

IMAGING FEATURES • The imaging features of 80 patients were evaluated with particular attention to characteristics that may aid in both diagnosis and localization.

RESULTS

MENINGOCOELE THROUGH CRIBRIFORM DEFECT Fusion CT MRI

MENINGOENCEPHALOCELE

DEVELOPING ENCEPHALOCELE

CSF LEAK WITHOUT ENCEPHALOCELE Fusion CT MRI

POINTED SULCUS SIGN The gathered sulci (thin orange arrow) aids in localizing the site of skull-based defect. In this case it “points” to the location of the defect. Beyond the defect, an encephalocele has formed within the frontal sinus (yellow arrow).

SPONTANEOUS CSF LEAK IN IIH • These patients may develop spontaneous CSF leaks • Identification of associated imaging manifestations may aid in the diagnosis • These associated findings include: • Expanded empty sella • Enlarged Meckel’s cave • Enlarged arachnoid granulations • Arachnoid pitting • Dural ectasia • Optic sheath dilatation

EMPTY SELLA Note the small tuberculum meningioma (arrow)

ARACHNOID PITTING

OPTIC SHEATH ECTASIA AND LARGE MECKEL’S CAVE

PITFALLS • Use of a magnet with a lower field strength significantly limits accurate diagnosis 1. 5 T 3. 0 T

CONCLUSION

SKULL-BASED DEFECT ASSESSMENT • • • Clear gap/defect in osseous density in skull base, esp. : • Cribriform • Planum sphenoidale • Sellar floor • Petrous apex • Pterygoid recess of sphenoid Meningocele, encephalocele, or meningoencephalocele can be seen • Although patient can have CSF leak in the absence of the above. Fluid channeling through or in close proximity to defect, esp: • Superior olfactory recess • Ethmoid cells • Sphenoid cells (including pterygoid recess) • Petrous apex into mastoid complex Change in fluid over time (between early and late scan) Ancillary findings suggestive of IIH, such as • Arachnoid granulations • Empty sella

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