Idiopathic intracranial hypertension presenting as bilateral spontaneous lateral intrasphenoidal and transethmoidal meningoceles: a case report and review of the literature

Background Basal meningoceles are rare herniations of the meninges that tend to present unilaterally with cerebrospinal fluid rhinorrhea. Growing evidence suggests that intracranial hypertension contributes considerably to the formation of spontaneous basal meningoceles. Case presentation A 50-year-old man of Middle East ethnicity presented with a 16-week history of cerebrospinal fluid rhinorrhea, short-term memory loss, and slight decline in cognitive function. We present a case of bilateral spontaneous meningoceles with bone defects in the left lateral sphenoid sinus and right anterior cribriform plate, as well as with a remodeled sella. A neuronavigation-assisted expanded endoscopic endonasal surgery was performed to resect the meningoceles. Postoperative imaging demonstrated complete resolution of the bilateral meningoceles. Conclusions This case reports the first bilateral basal spontaneous meningoceles in the literature. Furthermore, based on this case’s imaging results and the literature reviewed, elevated intracranial pressure may be a determining factor behind the development of spontaneous meningoceles.


Background
Basal meningocele is a herniation of the meninges through a defect in the bone of the skull base. This disorder almost invariably presents with cerebrospinal fluid (CSF) rhinorrhea, and the clinical history may also include headache, vertigo, seizures, and meningitis [1]. The etiology behind spontaneous forms of this disorder has been debated; however, recent evidence points to increased intracranial pressure (ICP) as a driving cause [2]. Most spontaneous basal meningoceles present unilaterally with CSF rhinorrhea in adults. We present a case of bilateral spontaneous left lateral intrasphenoidal and right transethmoidal meningoceles in a 50-year-old man. This is a rare finding in which two types of skull base lesions present concurrently in an adult patient with no previous history of nasal surgery or trauma.

Case presentation
A 50-year-old man of Middle East ethnicity presented with a 16-week history of CSF rhinorrhea, short-term memory loss, and slight decline in cognitive function. On physical examination, clear watery rhinorrhea, right-beating nystagmus, tongue deviation to the left side, mild facial asymmetry, multiple lipomas, bradycardia (52 beats/minute), and high blood pressure (194/118 mmHg) were detected. Laboratory tests results revealed presence of beta-2 transferrin in rhinorrhea fluid and hypokalemia (3 mmol/L). There were no other abnormalities in his hematology (for example, blood count) and chemistry test results (for example, liver function and CSF analysis). His past medical history was significant for: hypertension; Dercum's disease; right internal carotid dissection with pseudoaneurysm formation which was stable and conservatively treated, and followed with imaging; chronic compensated noncommunicating hydrocephalus secondary to obstruction at aqueduct of Sylvius, and a one-time seizure episode.
Computed tomography (CT) showed bony defects in his left lateral sphenoid sinus and right anterior cribriform plate (Fig. 1). CT cisternography revealed adjacent meningocele to the aforementioned defects with pooling of intrathecal contrast, confirming herniation into the left lateral sphenoid and right anterior ethmoid air cells.
Magnetic resonance imaging (MRI) demonstrated a 2.9 × 1.8 × 1.8 cm right anterior meningocele traversing the anterior cribriform plate inferiorly into anterior ethmoid air cells and nasopharynx with extension into the right maxillary sinus (Fig. 2a). Another contrast extension from the left middle cranial fossa along its most anterior aspect into the most lateral aspect of the sphenoid sinus was identified suggesting a second meningocele measuring 1 × 1 × 0.9 cm (Fig. 2b). Both lesions were enhanced with gadolinium but no brain parenchyma could be identified within the sacs. Other findings on MRI included a significantly flattened pituitary gland within a remodeled sella and a slightly dilated ventricular system.
He underwent neuronavigation-assisted expanded endoscopic endonasal surgery with resection of the anterior skull base meningoceles. The first lesion was right ethmoidal and the second lesion was left sphenoidal. Repair of the dura was carried out with two layers of dural matrix. Insertion of a lumbar drain was done to drain CSF and for injection of fluorescein to help confirm dural seal. Opening pressure upon insertion of the lumbar drain at the time of surgery was 20 mmHg. Septal and anterior ethmoidal flaps were used to support the repair of the sphenoid and anterior ethmoidal lesions, respectively. He recovered uneventfully and postoperative imaging showed complete resolution of the meningoceles bilaterally (Fig. 3).
Four weeks after the surgery, he presented to our clinic with CSF leak and headache. MRI revealed evidence of CSF leak noted within the left sphenoid sinus. He underwent an endoscopic repair of the CSF leak and insertion of a ventriculoperitoneal shunt. Postoperation, he recovered well and presented no symptoms. He had 3-year follow up with no recurrence of the meningoceles.

Discussion
We presented a rare case of a 50-year-old man with bilateral spontaneous lateral intrasphenoidal and transethmoidal meningoceles with nasal herniation and CSF rhinorrhea, associated with a significantly flattened pituitary gland within a remodeled sella.
Nasal meningoceles are herniations of the meninges into the nasal cavity [3]. Similar complications include encephaloceles (only the brain tissue is herniated) and meningoencephaloceles (both brain and meningeal tissues herniate). The location of the bone defect in the skull defines whether a meningocele is frontal, occipital, parietal, or basal [4].
Our case reports a finding of bilateral meningoceles in an adult male involving both transethmoidal and lateral recess intrasphenoidal lesions. The bilateral nature of this lesion is a rare finding. As far as we know, no cases of bilateral, basal spontaneous meningoceles have been reported in the literature. However, seven cases of spontaneous bilateral meningoencephaloceles have been reported [2,9,28]. Of these, five patients had bilateral lateral recess intrasphenoidal meningoencephaloceles [2,9,28] (Table 1). No cases involved both transethmoidal and intrasphenoidal lesions. Thus, as far as we know, our case reports the first finding of bilateral basal spontaneous meningoceles in the literature. Furthermore, it depicts the first case of bilateral intrasphenoidal and transethmoidal defects with nasal herniation of any kind in the literature.
The etiology of basal meningoceles has historically been classed into congenital, iatrogenic, traumatic, and spontaneous causes [9]. Spontaneous cases almost invariably present as CSF rhinorrhea in adult patients [2, 6, 8-14, 16-24, 26, 28, 29]. The mean age of the 15 spontaneous transethmoidal reported cases was 46 at presentation [10][11][12][13][14]29]. Only one of these patient's histories did not include CSF rhinorrhea [29]. Similarly, the mean age of the 28 spontaneous intrasphenoidal reported cases was 51 with 15 showing signs of CSF rhinorrhea [5,6,8,[15][16][17][18][19][20][21][22][23][24][25][26][27] (Table 1). Traditionally, the spontaneous category was synonymous with idiopathic as it was reserved for CSF leaks that did not have a discernable cause [30]. However, recent literature strongly suggests that many spontaneous causes are the result of increased ICP [2]. One common sign of elevated ICP is empty sella syndrome. This is manifested radiologically as an empty sella due to compression of the pituitary gland as CSF replaces normal pituitary space [31]. Schlosser and Bolger found that all four of their patients with bilateral meningoencephaloceles had positive empty sella syndrome on radiography [9]. On MRI, we found a significantly flattened pituitary gland within a remodeled sella, indicative of empty sella syndrome as well. This finding, in the absence of congenital, tumor, or traumatic etiology, may strengthen the argument that elevated ICP is implicated in the formation of a spontaneous meningocele.

Conclusion
Our case reports the first spontaneous bilateral left lateral intrasphenoidal and right transethmoidal meningoceles in an adult male. This case highlights evidence that elevated ICP may be a determining factor behind spontaneous meningoceles.