Cerebrospinal fluid (CSF) leak diagnosed by computed tomography (CT) cisternography: accuracy is the key

A 63-year-old man with previous history of head trauma 20 years ago, started with 2-month left rhinoliquorrhea, getting worse when leaning forward. In addition, he presented postnasal drip, with throat irritation and cough.

The CT facial bones demonstrated multiple bone defects located in the right side of the frontal sinus, in the olfactory fossa towards ethmoid cells and in the left side of the sphenoid sinus both in the roof of this sinus and towards the sella turcica (Figure 1).

For the CT cisternography, lumbar puncture with intrathecal contrast administration was performed (Figure 2). The patient was then positioned in prone Trendelenburg position to facilitate the arrival of the contrast to the frontal region.

The CT cisternography showed CSF contrast leak in the left slope of the roof of the sphenoid sinus. The findings were evaluated with the patient in both prone and supine position (Figure 3). Our patient underwent transsphenoidal surgery which confirmed the CSF leak (figure 4) and it was repaired with a small sheet of resorbable material and two sheets of nasal cartilage. A complete resolution of symptoms was observed in the immediate postoperative period.

A cranial CSF leak or fistula consists in loss of CSF from the intracranial cavity secondary an osseous defect in the skull base. It is related to a disruption of the dura mater and adherent arachnoid mater, ending in a communication between the intracranial cavity and the nasal or ear cavity [1]. They are classified in three groups: traumatic, nontraumatic and spontaneous [1, 2]. Traumas which fracture the frontoethmoidal complex or the middle cranial fossa are the most common cause of CSF leaks. On the other hand, tumours from the pituitary gland are the most frequent cause of nontraumatic CSF leak. Finally, spontaneous CSF leak is more commonly found in obese middle-aged women [1, 2]. 

In the posttraumatic CSF leaks, 80% occur within the first 48 hours after injury [1]. Only a small part of patients will present rhinorrhoea decades after the trauma. However, persistent CSF leaks represent an increased risk of meningitis or encephalitis for the patient, requiring an early diagnose [1, 2].

The main goal of imaging is to precisely localize and characterize the defect, for correct surgical intervention. The CT facial bones are usually enough when a single leakage is the cause; nevertheless, multiple defects could represent a diagnose problem and a surgical challenge [1]. CT cisternography could help identify the exact site of leakage in patients with nonbone defect or multiple fractures or postoperative defects [3, 4].

The CT cisternography technique consists in two parts [1]. In the first one, a lumbar puncture is made for the administration of 3-10 ml of an iodinated non-ionic low-osmolar contrast agent. Afterwards, the patient is placed in a Trendelenburg position to opacify the basal cisterns. A prone position is recommended. The cranial flow of contrast material is confirmed with fluoroscopy.

The second part is the CT scan, obtaining images in both prone and supine positions through the region of interest. A positive result involves the presence of a skull base defect and contrast opacification within the sinus or nasal cavity [1, 2].

However, the usefulness of the CT cisternography is limited to actively leaking of CSF and its sensitivity is variable in intermittent CSF leaks [1, 3]. Also, low-osmolarity contrast agents have the possibility of side effects like headache, meningeal irritation, and seizures, although they have an exceptionally low incidence [1].

Take home message: CT cisternography could precisely identify the CSF leak in misdiagnosed patients, helping surgical management.