Teaching Case

The patient was admitted to hospital because of intense headache, obnubilation without fever and vomiting, developed over 5-6 hours.

The patient’s symptoms were intense headache, vomiting and general unwellness with obnubilation. No relevant medical history except for arterial hypertension under medical treatment. Following examination, the patient reported a stiff neck and watery rhinorrhoea through the right nostril, occurring now for a week, with no history of trauma. This suggested the need for an MR (Fig. 1) as the CT was out of order at the time. The patient underwent subsequent lumbar puncture with a diagnosis of bacterial meningitis, probably pneumococcal, for which antibiotic treatment was started with a good clinical development. During hospitalization, the patient showed persistent, abundant rhinorrhoea with high glucose levels in the nasal fluid, testing positive for beta-2 transferrin protein, implying the presence of cerebrospinal fluid (CSF). A high resolution CT was carried out in the axial (Fig. 2) and coronal (Fig. 3) planes, showing a bone defect on the side wall of the right sphenoid sinus. Good ongoing clinical development with persistent rhinorrhoea, culminating in surgical closure of the fistula, confirmed to be located at the side wall level of the right sphenoid sinus. The fistula closure was performed three weeks after admittance by nasal endoscopy, using a nasal septum cartilage graft with a mucoperichondrial flap, showing good post-surgical development, with the fistula closing after the first attempt. The patient now shows no rhinorrhoea or any other symptoms, more than 1 year after surgery.

Cerebrospinal fluid (CSF) fistulas with rhinorrhoea can be associated with meningitis, as in the present case, for which the surgical closure of the causative fistula is advisable following the exact anatomic localisation of the osseous/dural defect. The determination of beta-2 transferrin protein in the nasal fluid is a simple and very specific test for the presence of cerebrospinal fluid, for which in uncertain clinical cases, negativity can prevent unnecessary image studies. The most common site of CSF leakage is through the floor of the anterior cranial fossa, connecting the ethmoidal or frontal sinus with the nasal cavities. Spontaneous fistulas of the sphenoid sinuses (frequently associated with the empty sella turcica) are rare, and occur mainly at the junction between the lateral wall and the floor of the middle cranial fossa. This is more frequent in cases of large lateral sphenoid recess with point erosions (arachnoid pits), although, as in our case, these can appear in the mid-area of the side wall or in other locations such as, in exceptional cases, through the clivus. The best imaging method to visualize bone defect is the high resolution CT, although diagnosis also requires thickened adjacent mucosa and/or partial or total occupation of the sinus. The study protocol for the CT of fistulas with rhinorrhoea should include all paranasal sinuses (3- mm -thick) in the coronal plane, from frontal to sphenoid sinuses in prone position, and sometimes 1-1.5 mm thick in one or more planes in the area in question, with a bone reconstruction algorithm and a 120 mm field of view (FOV). The MR cisternography, as well as having a multiplanar capacity and being free from ionizing radiations, is another non-invasive imaging method useful in the localisation of active fistulas, which can supplement the CT through its capacity to show the presence of extracranial cerebrospinal fluid and the occurrence of possible cerebral herniation (encephalocele) through the fistula. The development of different minimally invasive surgical techniques (nasal endoscopic approach), with a limited field of visualization, makes an accurate localisation necessary.