Large Cystic Hypoglossal Schwannoma with Fluid-Fluid Level: A Case Report

Abstract

Hypoglossal schwannomas are rare skull base tumors. Furthermore, cystic hypoglossal schwannomas are extremely uncommon. We report the first case of a large cystic hypoglossal schwannoma with a fluid-fluid level. A 36-year-old woman presented with increased intracranial pressure and cerebellar signs without hypoglossal nerve palsy. Magnetic resonance imaging showed a predominantly cystic mass with a fluid-fluid level in the foramen magnum region extending into the hypoglossal canal. The intracranial tumor was largely removed via a midline suboccipital subtonsillar approach, leaving only a tiny residue in the hypoglossal canal. Histology confirmed a schwannoma with relative hypervascularity. Twenty months later, the tumor recurred and presented as a multicystic dumbbell-shaped lesion, extending intra-and extracranially through the enlarged hypoglossal canal. A complete resection of the intracranial and intracanalicular parts of the tumor was achieved with a small extracranial remnant treated by radiosurgery. Histology revealed a focal increased K i 67 proliferative index. In this report, we discuss the possible reasons for the absence of hypoglossal nerve palsy and the potential mechanism of the formation of the fluid-fluid level, and we consider the treatment of this lesion.KEYWORDS: Hypoglossal schwannoma, cystic, fluid-fluid level, schwannoma Schwannomas are benign, slow-growing neoplasms of the myelin-producing Schwann cells in the peripheral sensorimotor nervous system. In more than 90% of cases, these present as vestibular schwannomas. 1Schwannomas that arise from the hypoglossal nerve, a pure motor nerve, are very rare, accounting for only 5% of all nonacoustic intracranial schwannomas. 2 To date, around 100 cases of hypoglossal schwannoma have been reported in the English literature. Hypoglossal schwannoma usually originates intracranially but can also extend extracranially through the hypoglossal canal in a so-called ''dumbbell'' fashion or can arise purely from the extracranial portion of the XII nerve. According to Kaye et al's 4 classification of the jugular foramen neurinomas, the hypoglossal schwannomas documented in the literature are divided into three types: type A, intracranial in 31.5%; type B, dumbbellshaped or extra-and intracranial in 50%; type C, extracranial in 18.5%. 5Schwannomas are frequently solid masses, and cystic patterns are uncommon. A fluid-fluid level has been observed in a few intracranial cystic schwannomas on magnetic resonance image (MRI), such as schwannomas that originate from the V, VIII, and IX nerves. 6-8Here we describe a unique case of a monocystic hypoglossal schwannoma with fluid-fluid level. To our

Schwannoma of the hypoglossal nerve: Review of the literature based on an illustrative case

“…In almost all cases, there are varying degrees of paresis of the HyN, which appear as ipsilateral deviation, hemiatrophy and fasciculations of the tongue. These symptoms may be accompanied by hoarseness, intermittent-to-persistent headaches, dysarthria, slurred speech, swallowing difficulties and throat cramps (2,4,(9)(10)(11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21)(22)(23)(24)(25)(26)(27)(28). Whereas the effects on the specific functions of the nerve may be attributable to the local damage of the tumour on the nerve, these types of lesions, particularly when they increase in volume, may determine mass effects on surrounding or adjacent structures; for example, Mariniello et al (19) reported on the case of a patient who exhibited signs of cerebellar ataxia, right-sided hypotonia and increased intracranial pressure.…”

Multicystic vestibular schwannomas with fluid-fluid levels: A report of three cases

“…The second proposed mechanism is hemorrhage, typically of unclotted blood. The red blood cells or the products of red blood cell breakdown constitute the inferior fluid layer, while serous blood constitutes the superior fluid layer based upon sedimentation (2, 4,6,8,14). The present authors consider the second mechanism to be more accurate, since unclotted blood was observed in all the cases reported in the current study.…”

“…Therefore, surgery is the optimal treatment strategy for such patients. Although cystic VSs with fluid-fluid levels indicate greater adhesiveness, it is essential that total resection is performed during the initial surgical procedure due to the tendency for accelerated regrowth of residual cystic schwannoma (8,18).…”

“…Fluid-fluid levels in tumors display a radiological appearance of two fluid levels in the cystic section of tumors (4)(5)(6)(7)(8)(9)(10). This level is apparent on computed tomography (CT) and magnetic resonance imaging (MRI) scans, particularly on T2-weighted MRI scans (4)(5)(6)(7)(8)(9)(10)(11).…”

“…This level is apparent on computed tomography (CT) and magnetic resonance imaging (MRI) scans, particularly on T2-weighted MRI scans (4)(5)(6)(7)(8)(9)(10)(11). Previous studies have reported fluid-fluid levels in non-neurogenic tumors (4,5), as well as a small number of cranial nerve schwannomas, including trigeminal, glossopharyngeal and hypoglossal schwannomas (6)(7)(8). However, cystic VSs with fluid-fluid levels are fairly rare (3,6,9,10).…”