CSF Rhinorrhoea
Precise confirmation and localization ofCSF leakage is often difficult and challenging problem. Pin pointing the exact anatomical site is important in deciding the surgical approach and on success of the procedure. Although the present day radiological diagnosis of CSF rhinorrhoea is based on CT and MRI a battery of other modalities like Plain X-ray, tomogram and Radioisotope studies are used:
Plain X-ray: May demonstrate fluid level in sphenoid sinus, enlarged sella.pneumoencephalus, bony defects and fractures. Pluridirectional tomography : Delineate bony defects better and is of particular value in traumatic leaks and in high pressure leaks and non traumatic leaks.
Pneumo-encephalography : Introduction of air into subarachnoid space either through lumbar puncture or into ventricles show a dilated intrasellar subarachnoid pockets or anterior leaks commonly with the ventricles.
.Radioisotope study : Radioactive dyes introduced into CSF and its detection in nasal cavity was used to detect the site of leak and confirm the leak. 99mTC labeled, chelated 169Y6 labeled diphosphothiamine
radioactive sodium have been used in the past.
CT cisternography and HRCT: are new standard imaging modalities. CTC identifies the contrast medium either within the sinuses or passing through the bony defects. Its sensitivity varies from 36 - 60%. Usual
contrast used now is Omnipaque. Metrizamide causes many side effects like headache, vomiting and is not preferred now, HRCT has sensitivity of 50-60%. It's draw back is high radiation dose especially to the lens.
MR Cisternography: Is recently being increasingly used to diagnose the CSF leak site. CSF gives a high signal on a T2 weighted image. The demonstration of high signal through cribriform plate and paranasal
sinuses which is continuous with and similar to that of CSF in basal cistern is diagnostic of fistula. MRI also may show presence ofherniated brain parenchyma through the bony defect. Mucosal inflammatory thickening may be mistaken for CSF and can be differentiated using Gadolinium contrast which enhances the inflammatory tissue. This investigation is fast, non-invasive and causes no radiation related risks.
Fig. : Coronal section: Anterior skull base defect resulting in CSF Rhinorrhoea.
Fig. : Coronal section: Anterior skull base defect resulting in CSF Rhinorrhoea.
Fig. : Coronal section: Anterior skull base defect resulting in CSF Rhinorrhoea. |
