Sodium fluorescein is a dye used as a diagnostic agent in various medical specialties.

Neurosurgical use

In neurosurgery, sodium fluorescein is used for a few different diagnostic applications:

Vascular visualization in vascular neurosurgery[^2]:

Aneurysm clipping, sodium fluorescein — Vascular visualization with sodium fluorescein (right image) and without sodium fluorescein on the left after clipping of an intracerebral aneurysm. Figure adapted from Zhao, Xiaochun, et al. Application of fluorescein fluorescence in vascular neurosurgery. Frontiers in Surgery 6 (2019): 52.

Resection of Brain metastases[^3]:

Sodium fluorescein, brain metastasis — Visualization of the brain surface with a superficial brain metastasis stained by sodium fluorescein, clearly distinguishable from the surrounding brain tissue. Figure adapted from: Kerschbaumer, Johannes, et al. Mind the gap—the use of sodium fluoresceine for resection of brain metastases to improve the resection rate. Acta Neurochirurgica 165.1 (2023): 225–230.

Detection of CSF fistulas[^4]:

Sodium fluorescein, CSF fistula — Use of sodium fluorescein to detect a CSF fistula. Figure adapted from Lozano, P. A., et al. Hypodense sodium fluorescein for diagnosis and skull base cerebrospinal fluid leak repair. J Otolaryng Head Neck Surg 4 (2018): 023.

Figure

Intrathecal administration

In neurosurgery and otolaryngology, diluted sodium fluorescein solutions are used to localize CSF fistulas. It is administered intrathecally. For the detection of intracranial CSF fistulas, the fluorescein is ideally diluted in a fluid that is hypodense relative to CSF, allowing the sodium fluorescein to distribute more effectively[^4] [^5].

Sodium fluorescein diluted in:	Density	Density compared with CSF	Characteristics
10ml double-distilled water	1.001	Hypodense	Appears in the surgical field shortly after administration.
10ml sterile water	1.003	Hypodense	Appears in the surgical field several minutes after administration.
10ml Cerebrospinal fluid	1.005	Hyperdense	Appears in the surgical field after approximately 60-90 minutes while the patient is in the Trendelenburg position.
10ml normal saline	1.006	Hyperdense	Appears in the surgical field after 60-90 minutes while the patient is in the Trendelenburg position, with rapid absorption by the villi of the Choroid plexus.

Intrathecal dosage

For intrathecal administration, the literature predominantly recommends a dose of 0.1 ml of a 5% fluorescein solution per 10 kg of body weight. This is diluted with one of the carrier solutions listed in the table above to a total volume of 10 ml. The maximum dose should not exceed 1 ml of the 5% fluorescein solution, as serious complications following intrathecal administration have been documented at higher doses[^1].