Nasal Meningocele

Diagnosis

Physicians can be faced with two main different scenarios: patients with persistent or intermittent watery rhinorrhea highly suggestive for CSF leak and patients who had one or more bouts of meningitis apparently without any specific cause. In the first situation, which is the most frequent, diagnosis should include first chemical methods to analyze the nasal discharge in order to obtain confirmation of its nature, while in the second an immediate imaging examination and fluorescein test are indicated (Fig. 7.2).

Csf Test For Leak

Fig. 7.2. Work-up in the case of suspected spontaneous or traumatic CSF leak. High resolution CT (HRCT)

Fig. 7.1. Meningocele of the left nasal fossa. Endoscopic evaluation with a 0°-angled rigid endoscope: an isolated bluish polypoid mass (P) projecting from the left olfactory fossa is visible. Nasal septum, NS; middle turbinate, MT

Fig. 7.2. Work-up in the case of suspected spontaneous or traumatic CSF leak. High resolution CT (HRCT)

Chemical methods for glucose, protein, or chloride have been used for many years to confirm CSF leak. However, they are nowadays considered highly nonspecific (Oberascher and Arrer 1986) and beta-2 transferrin (B2T) assay has taken their place in the confirmation of CSF rhinorrhea diagnosis. B2T is a polypeptide involved in ferrous ion transport: while beta-1 transferrin is present in serum, nasal secretions, tears, and saliva, B2T has been demonstrated in CSF, perilymph, and aqueous humor only. The reported sensitivity and specificity for B2T test in the diagnosis of CSF rhinorrhea is 100% and 95%, respectively (Nandapalan et al. 1996; Skedros et al. 1993). Furthermore, the procedure is absolutely non-invasive, the amount of fluid necessary for analysis is very small (0.5 ml), detection of B2T can be achieved within 3 h, and contamination by other body fluids does not invalidate the method. Beta-trace protein (BTP) is another brain specific protein that is produced mainly in the leptomeninges and the choroid plexus; it is the second most abundant protein in CSF after albumin. This protein has also been detected in other body fluids such as serum and perilymph at much lower concentrations than in CSF. Recently, a BTP nephelometric assay for the quantification and detection of CSF in nasal fluid has shown sensitivity of 91.17% and specificity of 100% (Bachmann et al. 2000). Compared with B2T assay, BTP assay is less time-consuming . Therefore, B2T and BTP assays are nowadays considered the first line test in confirming the diagnosis of CSF rhinorrhea.

The recommended fluorescein test protocol is based on the employment of 1 ml of 5% sodium fluorescein solution diluted with 10 ml of patient's CSF. The patient is put in Trendelenburg position and the solution is slowly injected intrathecally through a lumbar puncture (Stammberger 1991). Rare adverse effects of intrathecal injection of fluorescein have been reported (temporary paresthesias of the lower limbs, weakness of the extremities, dizziness, dyspha-sia, hemiparesis and status epilepticus) (Moseley et al. 1978); however, the occurrence of these symptoms seems to be related to the use of higher concentrated solutions of the dye (Senior et al. 2001).

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