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Spontaneous Temporal Lobe Encephalocele Within the Sphenoid Sinus

Mohammed Dhaha1, Abdelhafidh Sliman2, Nadhir Karmeni2, Sawsen Dhambri, Jalel Kallel2

1 Institut Salah-Azaiz, Tunis, Tunisia.

2 National Institute of Neurology, Tunis, Tunisia.

Correspondence to: Dr. Mohammed Dhaha, Email: dhaha.mohamed87@gmail.com

Received: 18 November 2019; Revised: 22 March 2020; Accepted: 08 May 2020; Available online: 21 June 2020

 

Summary

Encephaloceles are herniation of cranial content arising from a skull defect. Encephaloceles of the lateral wall of the sphenoid sinus (ELWSS) are uncommon events. In most cases, these cranial hernias are secondary to trauma and craniofacial surgery. Spontaneous forms are even rarer and not well understood. The most adopted hypothesis is a persisting Sternberg’s canal, an embryonic remnant connecting the middle cranial fossa and the nasopharynx. ELWSS are usually revealed by cerebrospinal fluid (CSF) leak. Diagnosis of this disease necessitates quick management due to the potential of lethal complications such as meningitis. We report the case of a spontaneous ELWSS in a 53- year-old woman revealed by CSF leak which was successfully managed with a conventional transcranial approach. We focus on the clinical aspect and pathogenesis of the disease, and discuss the main possible surgical approaches.

 

Keywords: Spontaneous encephalocele, Sphenoid sinus, CSF leak, Transcranial approach

Ann Afr Surg. 2021; 18(1):63–66

DOI: http://dx.doi.org/10.4314/aas.v18i1.12

Conflicts of Interest: None

Funding: None

© 2021 Author. This work is licensed under the Creative Commons Attribution 4.0 International License.

Introduction

Cranial encephaloceles are herniation of cranial content arising from a defect of the anterior, posterior or middle cranial fossae. Basal encephaloceles are uncommon events with an incidence almost reaching 1 in 35,000– 40,000 people (1,2). Intra-sphenoidal encephaloceles usually arise from the superior and posterior wall. Lateral localization or parasellar form is even rarer and consists of the protrusion of inferior temporal lobe tissue into the sphenoid sinus. Few scattered case reports have been reported in the literature concerning this rare event (2-5). This lesion is usually secondary to trauma and surgery. Spontaneous cases are still not well understood. One of the most relevant hypotheses proposed was related to a persisting craniopharyngeal canal called Sternberg’s canal (6). It starts from the sphenoid bone body and the lesser wing and goes downwards to the nasopharynx, creating a connection between the middle cranial fossa and the sphenoid sinus. Encephalocele of the lateral wall of the sphenoid sinus (ELWSS) mainly manifests with CSF rhinorrhea. Meningitis and seizures were also reported (7). This clinical diversity made this pathological entity a multidisciplinary topic, uniting otolaryngologists, neurosurgeons and maxillofacial surgeons.

We report an illustrative case of spontaneous ELWSS in a 53-year-old woman revealed by CSF rhinorrhea, which was managed by a classical transcranial approach. In this paper, we describe the clinical aspect of the ELWSS and its possible pathogenesis. We describe the management of the disease using the classical approach and then discuss the different therapeutic approaches.

 

Case report

A 53-year-old post-menopausal woman was referred to the neurosurgery department of Mongi Hmida Institute for spontaneous CSF rhinorrhea evolving for three months. Hypertension and dyslipidemia were noted as associated comorbidities. No history of craniofacial trauma or surgery was reported. The patient was obese with a BMI equal to 33.9. Clinical examination found an isolated right CSF rhinorrhea. The patient had already been examined by a head and neck surgery team. Nasal endoscopy showed a clear liquid leak in the right nasal cavity, which was interpreted as CSF after beta transferrin test. CT scan and CT cysternography showed a lateral bony defect of the right wall of the sphenoid sinus associated with protrusion of temporal lobe tissue in the sphenoid sinus (Figures 1 and 2). The patient underwent transcranial resective surgery with dissection of the temporal lobe. The bony defect was identified and the encephalocele was resected. Autologous abdominal fat was already harvested and prepared after para umbilical incision. The defect was repaired using cranial bone and abdominal fat graft (Figures 3a and b). Postoperative recovery was uneventful. CSF dried up in 2 days. The patient was discharged after 3 days. She is asymptomatic after 1 year of follow-up.

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Discussion

Encephalocele of the lateral wall of the sphenoid sinus, also called parasellar sphenoid encephaloceles, consist of the herniation of meninges and brain tissue through a skull defect in the lateral recess of the sphenoid sinus laterally to the foramen rotundum (8). This herniation is either spontaneous or secondary to trauma and craniofacial surgery. Spontaneous ELWSS are rare conditions and limited in the literature to sporadic cases. The presence of a certain predisposing anatomic structure has been evoked as a probable hypothesis behind the genesis of ELWSS. In fact, the sphenoid bone derives from the fusion of several embryonic portions: presphenoid (anterior sphenoid bone), basisphenoid (posterior sphenoid bone), orbitosphenoid (lesser wings) and alisphenoid (lateral part of the sphenoid process and greater wings) (9). Ossification of some cartilaginous portions corresponding to the future lateral wall of the sphenoid sinus happens after birth. If this fusion fails, a connection is created between the middle cranial fossa and the rhinopharynx. This connection, described in 1888 by Sternberg, corresponds to the craniopharyngeal canal (10). Towards puberty, the sphenoid sinus reaches its final pneumatization. If bone reabsorption reaches the Sternberg canal, this represents a week point where encephaloceles can occur (6).

ELWSS are favored by enlargement of the sphenoid bone (6). Obesity, like in this case, has been also reporte