Early identification of CSF rhinorrhoea can reduce the risk of meningitis and potentially decrease the length of hospital stay. To determine the exact site of leak, intrathecal fluorescein (IF) is frequently used as a diagnostic tool adjunct to repair surgery in rhinorrhea. Although this is generally considered safe, there is a slight risk of seizures, radicular symptoms such as numbness and transient paraparesis.¹

Miss. AB, a 20 month old child weighing 11.6kg with history of traumatic subdural collections was admitted with episodes of absence seizures, ataxia and unresponsiveness. Initial investigations involved an electroencephalogram which reported a normal background rhythm. A follow up MRI scan reported no definite site of abnormal CSF leak to confirm the working diagnosis. Hence, IF was proposed as a diagnostic tool to identify the location of a possible leak. The pharmacist conducted a therapeutic review with the aim of appraising existing evidence for the use of IF in paediatrics.

A total of 12 articles were identified using Medline and Embase. 5 case series and 1 case report were selected for further review to determine the safety profile, optimal dose and appropriate formulation for the diagnostic procedure. Studies showed at lower concentrations, with doses ranging from 25-100mg the rate of minor complications such as nausea/vomiting, headache and dizziness was negligible.^{1 2} No complications were accounted in using the lowest dose (<25mg).² Another study specifically mentioned no adverse reactions observed in children when 0.1ml/kg of 5% fluorescein was administered.³ The case report presented a paediatric patient (16 months) with CSF leak who was administered 0.125ml (6.25mg) of 5% IT to identify the leak.⁴ The potential dosage for Miss. AB was decided as between 10mg to 25mg balancing the increasing risk of adverse reactions with higher doses and possibility of false-negative result with lower doses.

The neurosurgical team used this evidence to present the patient’s case to the chairman’s board for an off-label use approval at the trust. Upon enquiring various manufactures, the 5% unlicensed injection was unavailable to purchase and the 10% injection is unsuitable for intrathecal use. Therefore, the 20% fluorescence sodium injection which is an unlicensed ‘specials’ product usually used in adults was recommended by pharmacy. The smallest measurable dose of 0.1ml (20mg) of 20% fluorescein sodium, diluted in 10ml CSF with 5ml infused via a 0.2micron filter was recommended. The batch number and pyrogen free certificate was obtained from pharmacy procurement and application was submitted.

Upon receiving the panel approval, IF was used and a CSF leak was identified. This has aided the surgeons to confirm diagnosis and repair the rhinorrhea. With this successful intervention, the use of IF can be an established option to diagnose CSF rhinorrhea prior to surgery in the trust. These findings will be used in submitting a formulary application and drafting trust guidance for extending the use of IF to paediatrics as a diagnostic tool in neurosurgery.

References

1. Javadi S, Samimi H, Naderi F, et al. The use of low- dose intrathecal fluorescein in endoscopic repair of cerebrospinal fluid rhinorrhea. Archives of Iranian Medicine 2013;16:264-266.

2. Rainer K, Wienke A, Wolfgang D, et al. Use of sodium fluorescein solution for detection of cerebrospinal fluid fistulas: an analysis of 420 administrations and reported complications in Europe and the United States. Laryngoscope 2004;114:266-272.

3. Crosara P, Becker C, Stamm A, et al. Chemical and cytological analysis of cerebral spinal fluid after intrathecal injection of hypodense fluorescein. Brazilian Journal of Otorhinolaryngology 2015;81:549-553

4. Lue A, Manolidis S. Intrathecal fluorescein to localize cerebrospinal fluid leakage in Bilateral Mondini Dysplasia. Otology & Neurotology 2004;25:50-52.