Triggered episodic vestibular syndrome and transient loss of consciousness due to a retrostyloidal vagal schwannoma: a case report

Abstract

Background: Various conditions may trigger episodic vertigo or dizziness, with positional changes being the most frequently identified condition. In this study, we describe a rare case of triggered episodic vestibular syndrome (EVS) accompanied by transient loss of consciousness (TLOC) linked to retrostyloidal vagal schwannoma.

Case description: A 27-year woman with known vestibular migraine presented with a 19-month history of nausea, dysphagia, and odynophagia triggered by swallowing food and followed by recurrent TLOC. These symptoms occurred independently of her body position, resulting in a weight loss of 10 kg within 1 year and in an inability to work. An extensive cardiologic diagnostic work-up undertaken before she presented to the neurologic department was normal. On the fiberoptic endoscopic evaluation of swallowing, she showed a decreased sensitivity, a slight bulging of the right lateral pharyngeal wall, and a pathological pharyngeal squeeze maneuver without any further functional deficits. Quantitative vestibular testing revealed an intact peripheral-vestibular function, and electroencephalography was read as normal. On the brain MRI, a 16 x 15 x 12 mm lesion in the right retrostyloidal space suspicious of a vagal schwannoma was detected. Radiosurgery was preferred over surgical resection, as resection of tumors in the retrostyloid space bears the risk of intraoperative complications and may result in significant morbidity. A single radiosurgical procedure (stereotactic CyberKnife radiosurgery, 1 x 13Gy) accompanied by oral steroids was performed. On follow-up, a cessation of (pre)syncopes was noted 6 months after treatment. Only residual infrequent episodes of mild nausea were triggered by swallowing solid food remained. Brain MRI after 6 months demonstrated no progression of the lesion. In contrast, migraine headaches associated with dizziness remained frequent.

Discussion: Distinguishing triggered and spontaneous EVS is important, and identifying specific triggers by structured history-taking is essential. Episodes being elicited by swallowing solid foods and accompanied by (near) TLOC should initiate a thorough search for vagal schwannoma, as symptoms are often disabling, and targeted treatment is available. In the case presented here, cessation of (pre)syncopes and significant reduction of nausea triggered by swallowing was noted with a 6-month delay, illustrating the advantages (no surgical complications) and disadvantages (delayed treatment response) of first-line radiotherapy in vagal schwannoma treatment.

Keywords: case report; dizziness; dysphagia; radiotherapy; transient loss of consciousness.

Figure 1

Illustration of the timeline of events, with reported complaints, diagnostic testing, and treatments is shown separately. CE, contrast-enhancing; CTA, computed tomography angiography EEG, electroencephalography; FEES, fiberoptic endoscopic evaluation of swallowing; Gy, gray; Ga-DOTA, gallium 68 labeled 1,4,7,10-tetraazacyclododecane-tetraacetic acid; MRI, magnetic resonance imaging; PET/CT, positron emission tomography/computed tomography; SSTR2, somatostatin receptor 2; TLOC, transient loss of consciousness.

Figure 2

Illustration of the vagal schwannoma on brain MRI (axial, sagittal, and coronal post-contrast T1 volumetric interpolated breath-hold examination (VIBE) sequences) before treatment (A–C) and on follow-up, 6 months after treatment (D–F). On initial imaging, a contrast-enhancing solid mass (marked with white arrows) in the right retrostyloid space in both the axial (A), sagittal (B), and coronal (C) plane can be seen. On follow-up, the solid mass is unchanged in size and morphology. Courtesy of MRI images (A–C): Bilddiagnostik Basel, Switzerland.