The patient went on to have magnetic resonance imaging (MRI) and computed tomography (CT) scans following intrathecal infusion of metrizamide that are seen in Fig. 69.1 and Fig. 69.2. Ear, nose, and throat (ENT) service demonstrated a mass in the upper nasopharynx using fiberoptic endoscopy of the nasal cavity.

• Spontaneous CSF fistulas may occur remotely following skull-base head trauma in any area of persistent outpouching, or dural defect through a fracture site.
  
• They may occur in the spine as part of a remote trauma or pseudomeningocele or a spontaneous dural sleeve rupture.
  
• Congenital arachnoid cysts, spinal Tarlov or arachnoid cysts, or congenital encephaloceles may also chronically or acutely leak CSF.
  
• CSF leaks have also been reported due to congenital defects in the middle ear.¹

• CSF leak may occur in any area with one of the above pathologies, but obviously occult leaks into the nasal cavity or from the spine into the epidural or lumbar fascial compartments may occur and may be difficult to detect.

• CSF fistula might result in CSF infection as in this case. Any chronic communication between the environment and meningeal space may produce acute, recurrent or chronic meningitis or other central nervous system (CNS) infections.
  
• Low-pressure headache may also be attributable to a chronic CSF leak.²
  
• Finally, superficial hemosiderosis has been reported following chronic CSF fistula into a traumatic pseudomeningocele with neovascularization and repeated hemorrhage. This could obviously present with mental deterioration, hearing, balance loss, and other cranial nerve deficits.^3,4

• In a patient where CSF fistula is suspected, an MRI scan of the complete neuraxis would be imperative. In some instances this may not be diagnostic.²
  
• A CT scan can be helpful to demonstrate bone defects. Cisternal infusion of contrast media followed by a thin-cut CT, might be able to demonstrate extra CNS flow of fluid.²
  
• In rare instances, a nuclear medicine study with lumbar cisternal infusion of radionucleotide tracer may also be used to demonstrate a small or slow communication, though with less anatomic detail.¹

• The coronal T2-weighted MRI scan and the coronal reconstruction of the postcisternal infusion of contrast CT scan both show a defect in the ethmoidal bone of the frontal cranial fossa with herniation of tissue and CSF through the defect into the nasal cavity.

• There are essentially two surgical approaches to this lesion.
  
  
  
  • A bifrontal craniotomy with repair of the defect from above using bone, muscle graft, and a vascularized pericranial flap would be possible. This might be possible entirely with an extradural approach, but an intradural inlay graft might protect better against CSF leak.^1,2
    
  • Alternatively, there is significant experience in some centers with an entirely endoscopic intranasal approach to the repair of this lesion with again vascularized mucosal flap and an inlay graft if possible.⁵