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Skull Base CSF Leak


KEY FACTS

Imaging

  • Best clue

    • Anterior or central skull base ( SB ) defect on bone CT with positive β2-transferrin test on nasal secretions

  • Anterior SB bone CT findings

    • Bone defect in cribriform plate, lateral lamella of middle turbinate or ethmoid roof

    • Other evidence for fracture, functional endoscopic sinus surgery (FESS), congenital cephalocele

  • Central SB bone CT findings

    • Bone defect in sella floor (transnasal pituitary surgery, craniopharyngeal canal persistence), lateral wall sphenoid (arachnoid granulation)

Top Differential Diagnoses

  • Vasomotor rhinitis

  • SB defect without cerebrospinal fluid (CSF) leak

Pathology

  • Can be congenital or acquired (post trauma, surgery)

  • Congenital CSF leak

    • Cribriform plate defect, congenital cephalocele, persistent craniopharyngeal canal

  • Acquired leak: From arachnoid granulation (pit, osteodural defect) or “spontaneous”

    • Lateral roof of sphenoid sinus

  • Posttraumatic leak: Can occur with any sinonasal fracture

    • Roof or lateral wall of sphenoid sinus or cribriform plate/ethmoid roof

  • Postoperative defect: Can occur after any sinonasal or anterior or central SB surgery

Clinical Issues

  • Rhinorrhea with Valsalva or head-down maneuvers

  • β2-transferrin is single best test to confirm fluid from nose is CSF

  • Persistent CSF leaks endoscopically repaired

Coronal bone CT shows large bony defect
in left ethmoid roof, lateral to insertion of middle turbinate. Because there is complete opacification of the ethmoid cells, an MR was performed that showed meningoencephalocele.

Coronal bone CT after intrathecal contrast placement shows CSF
in left sphenoid chamber, bone defect
, and contrast extending through defect
. CT-cisternography is rarely necessary when high-resolution bone CT and MR are performed 1st for CSF leak.

Coronal T2WI MR reveals lateral wing of sphenoid sinus filled with CSF
. Osseous defect is in roof of lateral sphenoid roof
, and brain herniates through defect
. This woman had a “spontaneous” CSF leak. Many such leaks are caused by large arachnoid granulations.

Coronal T1WI C+ MR in the same patient shows peripheral enhancement
on the margin of the sphenoid meningoencephalocele. Note diffuse thin dural enhancement
, including at the defect site, secondary to leak.

IMAGING

General Features

  • Best diagnostic clue

    • Anterior or central skull base (SB) defect on bone CT, ± fluid level or opacified sinus with positive β2-transferrin test on nasal secretions

  • Location

    • Anterior SB: Cribriform plate, lateral lamella, ethmoid roof (fovea ethmoidalis)

    • Central SB: Sella floor, lateral sphenoid sinus wall in pneumatized inferolateral recess

  • Size

    • Depends on etiology but ranges from 2-3 mm to ≥ 10 mm

  • Morphology

    • Depends on etiology

      • –

        Smallest 3 mm, especially following closed head injury

      • –

        Larger defects postoperative (especially trans-sphenoidal approach to pituitary macroadenoma)

Imaging Recommendations

  • Best imaging tool

    • Bone CT with multiplanar reformations

      • –

        Large defects easily visualized on multiplanar CT obviating need for CT-cisternography

      • –

        Small, < 4 mm defects difficult to see, especially if present in bone that is normally thin

        • □

          May require CT-cisternography

    • MR used if cephalocele suspected

      • –

        Coronal sequences key: Estimate defect size & presence or absence of cephalocele

    • CT-cisternogram indicated if > 1 potential site of leak or CSF leak with no site seen on bone CT

      • –

        Positive study much more likely if patient leaking day of study

      • –

        Be sure to scan SB base prior to intrathecal nonionic contrast as osteoneogenesis can mimic contrast in sinus cavity

      • –

        After LP & intrathecal contrast placed, have patient do maneuvers that ↑ rhinorrhea

      • –

        Be sure to do CT scan prone after cisternogram portion to best see contrast column extending from subarachnoid space into sinus cavity

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