Spontaneous cerebroespinal fluid fistula associated with sphenoid meningoencephalocele

Clinical History

The patient presented with dizziness and vertigo, temporo-occipital oppression and abundant rhinorrhea of the left nostril of 12 hours of evolution. Normal neurological examination. Nasal liquid analysis: glucose cell count and total protein were normal. β2-transferrin assay: positive. Liquorrhoea was confirmed. Cranial CT and MRI were performed.

Imaging Findings

Cranial and sinus CT showed an expansive bone injury on the left sphenoid area (40 mm) with a continuity solution (12 mm) in the superior wall of the sphenoid bone and communication with the left coana. There was a heterogeneous soft tissue component within the damaged area, with calcifications and thin septums without significant post-contrast enhancement (Fig. 1).
To differentiate between primary brain injury and bone injury, MRI study was performed.
Skull base MRI identified an extension of intracranial meningeal tissue with cerebrospinal fluid (CSF) and part of the left medial temporal gyrus herniated through the large bone defect into the body of the left sphenoid bone. Secondarily, it communicated with the sphenoid sinus and with the coana. (Fig. 2)

Discussion

CSF fistulas may be congenital or acquired. Acquired fistulas can be classified as spontaneous, traumatic/iatrogenic and secondary. Traumatic/iatrogenic fistulas are the most common type (80-90%). In these cases, the clinical history associated with intermittent rhinorrhoea may suggest an osteodural defect with communication between intracranial structures and sinuses. Spontaneous fistulas frequency is increasing and its detection is much more complex currently. [1, 2, 3, 5]
Classically, they are described in middle-aged obese women with clinical symptoms and radiological signs of intracranial hypertension. It requires an initial clinical suspicion followed by laboratory confirmation of CSF leak and the subsequent use of imaging techniques (MDCT and MRI).
MDCT is usually the first test and shows the bone defect in the skull base associated with an air-fluid level or an opacification in the next cavity (Fig. 1d). But CT has its own limitations. There can be unnoticed small bone defects that are invisible with this technique and these only emerge if we use intrathecal contrast. In addition, CT cannot characterize the soft tissue component. [4, 6]
In our case, MRI demonstrates the existence of a myelomeningocele in an expanded sphenoidal sinus and can exclude other causes such as a primary bone neoplasm (Fig. 2).

MR cisternography is an alternative imaging technique in cases in which liquorrhoea exists and fistula is not demonstrated. It is able to depict CSF fistulas by enhancing the fistulous tract. [4]
Imaging findings of both techniques (MDCT and MRI) can confirm the location of the focal bone defect, provide information about the contents of meninges and/or brain tissue and can provide an optimal anatomical study to set the most appropriate surgical treatment in each case. [7]

Surgical repair of spontaneous CSF fistulas is recommended to prevent meningitis, intracranial abscess, pneumoencephalus, and refractory seizures.
The surgical approach and grafting materials used are selected based on several factors: location and size of the bone defect, volume of herniated brain matter, presence of a recurrent leak, patient’s general medical condition, expectations of the patient and surgeon’s preference. Traditionally, a transcranial or open approach has been the definitive method for treating a CSF fistula. Nowadays, endoscopic surgery has become the standard approach for most patients because it has comparable to superior success rates and lower morbidity than intracranial procedures. [8, 9]
Imaging findings are not only useful in the diagnosis, but also greatly help the surgeon to plan the surgery and decide the most appropriate surgical technique in each case. [9]

Differential Diagnosis List

Final Diagnosis

Spontaneous sphenoid meningoencepahlocele with CSF fistula.

URL:	https://www.eurorad.org/case/12526
DOI:	10.1594/EURORAD/CASE.12526
ISSN:	1563-4086