Idiopathic Temporal Bone Encephalocele

Abstract

Meningoencephaloceles are herniations of brain tissue through dehiscences of the skull base. These skull defects are either acquired (otologic infection, trauma, surgery, neoplasia) or spontaneous. Spontaneous temporal bone meningoencephaloceles are quite rare conditions, usually congenital in origin presenting during childhood, and only occasionally idiopathic presenting during adulthood. We present a case of temporal bone meningoencephalocele of adult onset. The patient was treated with exploratory mastoidectomy, amputation of the herniated cele and closure of the defect with temporalis fascia and an inferiorly based pedicled muscular flap. No reconstruction of the bony defect was performed, as the layered closure was considered adequate. Twelve months' follow-up revealed no relapse of the condition or postoperative complications.KEYWORDS: Temporal bone, meningoencephalocele, brain herniation Meningoencephaloceles (MECs) are herniations of brain tissue, covered by meninges, via openings of the skull base. These bony dehiscences-and the resulting MECs-can be caused by various processes such as otologic infection, trauma, surgery, neoplasia, or may occur spontaneously (Table 1). Chronic otitis media and/or middle ear surgery are considered the main causative factor of MECs; Jackson et al 1 reported a series of 35 brain herniation cases, 88.6% of which were secondary to otologic infection and/or surgery. Spontaneous MECs are quite rare, with an incidence of about 8.6% among MECs. 2 Spontaneous MECs are either congenital in origin or are otherwise considered idiopathic presenting during adulthood. [2][3][4][5][6][7][8][9] In idiopathic cases they are usually located at the tegmen tympani or the tegmen mastoideum. We present an unusual case of tegmen tympani meningoencephalocele, which was occult until adulthood.

Spontaneous Skull Base Meningoencephaloceles and Cerebrospinal Fluid Fistulas

“…Both prominent arachnoid granulations and spontaneous CSF fistulas have a predilection for areas adjacent to substantially pneumatized paranasal sinuses, such as the midline or lateral wall of the sphenoid sinus, along the floor of the middle cranial fossa, the tegmen tympani, the roof of the Eustachian tube, and, rarely, in the jugular foramen and posterior fossa plate of the temporal bone, between the sigmoid sinus and the bone labyrinth (Fig 2). Other sites of inherent structural weakness in the skull base include natural locations, such as perforations in the cribriform plate and the fascia of the sellar diaphragm (1,(4)(5)(6)(13)(14)(15)(16)(17)(18)(19)(20)(21)23,(25)(26)(27)(28)(29). The pathogenesis of spontaneous CSF fistulas may also include other factors, such as osseous anatomic variations, aging, bone remodeling, recurrent infections, and low-grade inflammation, all of which may contribute to the development of multiple CSF fistulas that are either concomitantly or temporally separated (7,17,26).…”

“…The presence of a unilateral mass or opacity in the olfactory recess is rare in patients whose paranasal sinuses are clear and should raise suspicion for a CSF fistula unless it is associated with surgical changes or inflammatory sinus disease (32). A low-lying gyrus rectus has also been reported to be an indirect sign of CSF fistulas (Fig 4) (6,8,27,33). , foramen cecum (white arrow), superior orbital fissure (black arrow), and foramen rotundum (black arrowhead).…”

“…The most common sites of leakage are the tegmen tympani and tegmen mastoideum. Spontaneous CSF fistulas in the temporal bone and middle ear are usually related to prominent arachnoid granulations and are most common in the 7th decade of life (Figs 2, 3) (1,4,5,14,26,27,29,42).…”

“…Whereas traumatic CSF fistulas are usually obvious, spontaneous CSF fistulas are frequently overlooked because of their subtle, intermittent course and lack of external abnormalities, with a subsequent delay in diagnosis. Moreover, they may remain asymptomatic or be incidentally found at preoperative endoscopy or CT of the sinonasal region or temporal bone (1,(4)(5)(6)(10)(11)(12)27,30,41).…”

Transmastoid Cartilage Graft-Meningocele Temporal: Surgical Approach

“…It presented a success rate of 100%. Papanicolaou et al, [12] reported a case of meningocele treated with exploratory mastoidectomy, amputation of the herniated meningocele and closure of the defect with temporalis fascia and an inferiorly based pedunculated muscular flap [12].…”