Small spheno-ethmoidal meningoencephalocele versus ethmoidal mucocele in spontaneous intracranial hypotension

Abstract

Background: Meningoencephalocele is defined as an abnormal sac of brain tissue and meninges extending beyond natural skull margins, often leading to cerebrospinal fluid (CSF) leakage. When this condition arises in the spheno-ethmoidal region, the diagnosis becomes more challenging as it can be mistaken for other nasal pathologies, such as mucocele.

Research question: We show in this case report a non-congenital sphenoethmoidal meningoencephalocele causing rhinoliquoral fistula and spontaneous intracranial hypotension.

Results: this 65-year-old woman presented with sporadic rhinoliquorrhoea associated with orthostatic headache, nausea and dizziness. Brain MRI revealed a small lesion of an ethmoidal sinus, which was successfully treated with endoscopic endonasal surgery. Histology confirmed the presence of meningoencephalic tissue positive for S100 protein on immunohistochemistry.

Conclusions: When dealing with lesions of the paranasal sinuses in contact with the anterior skull base, rhinoliquorrhoea presence suggests meningoencephalocele. In dubious cases, a proper workup, including a thorough clinical history and neurological examination, specific imaging, and a direct search of CSF-like markers, is essential to support the differential diagnosis. In such cases, a transnasal endoscopic surgical approach is recommended to obtain a final histological diagnosis and to perform eventual dural plastic surgery.

Keywords: Cerebrospinal fluid leak; Meningoencephalocele; Mucocele; Orthostatic headache; Rhinoliquorrhoea; Spontaneous intracranial hypotension.

Fig. 1

A) Volumetric T1-weighted post-contrast (gadolinium) brain 1.5T MRI showing very subtle marks of intracranial hypotension in the sagittal plane, such as redundant pituitary enhancement (arrow) and slight reduction in ponto-mesencephalic angle (arrowhead). B) Volumetric T1-weighted 1.5T MRI with fat saturation without contrast showing on the axial plane a small cystic lesion close to the medial wall of the left orbit (arrow). C), D), E) Volumetric T2-weigthed 1.5T MRI images and F) volumetric computed tomography (CT) scan with bone reconstruction algorithm showing both on the sagittal and coronal plane a focal bone thinning with possible interruption (arrowhead) just above the small lesion (arrow). G), H) Phase-Sensitive Inversion Recovery (PSIR) and post-contrast T1-weighted 3T MRI images on the coronal plane showing that the cystic lesion (arrow) was associated with focal dural thinning or possibly interruption along the spheno-ethmoidal planum (arrowhead). I) Microscope view (Pentero Microscope with YELLOW 560 filter) demonstrating the fluorescence of the freshly excised lesion on the roof of an ethmoidal sinus after intrathecal fluorescein administration. J) Postoperative volumetric CT scan with bone reconstruction algorithm showing on the sagittal plane the surgical repair of the ostodural cleft. (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)

Fig. 2

Volumetric T1-weighted post-contrast (gadolinium) brain 1.5T MRI showing signs of intracranial hypotension: pituitary hyperemia (arrow) (A), pachymeningeal enhancement (A, B, C), venous distention sign with convexity of inferior contour of dominant transverse sinus (arrow) (C), abnormal pontomesencephalic (D) and lateral ventricular (T2-weighted) (F) angles, mamillopontine distance (E).