Hypoglossal Nerve Palsy Misdiagnosed as Tongue Tumor: A Rare Case of Calcified Hypoglossal Schwannoma

Abstract

The authors hereby present a case of a calcified schwannoma of the hypoglossal nerve, which led to hypoglossal nerve palsy initially misinterpreted as a tongue tumor. This paper reviews the presentation of schwannoma of the hypoglossal nerve and offers a novel perspective on this rare condition. Diagnostic pitfalls and the diagnostic-therapeutic value are also discussed.

Introduction

Hypoglossal nerve palsy(HNP) is a relatively uncommon condition that can present with a range of symptoms, including dysphagia, dysarthria, and tongue deviation. HNP can be caused by a variety of underlying conditions, like tumors, trauma, infection, and vascular lesions [1–3]. In some cases, hypoglossal nerve palsy may cause clinical signs, which can be misinterpreted as a primary tumor of the tongue. Thus leading to unnecessary investigations and interventions. This report describes the first documented case of calcified schwannomas of the HN missed and misinterpreted as a tongue tumor.

Case Report

A 60-year-old male presented to our Department with a 5 years-history of dysphagia, dysarthria, and tongue deviation to the left with tongue discolorations. The patient reported no history of trauma or recent illness. Clinically, the tongue appeared atrophic and swollen on the left side, with a non-painful likely ulcer lesion on the left middle dorsal surface of the tongue. It was approximately 1 cm in diameter with sloping edges and averted margins. The surrounding mucosa exhibited irregularly shaped erythematous areas, interspersed with pale regions(Fig. 1). No submucosal infiltrative lesions were revealed on palpation. The patient was found to have left-sided HNP, with weakness of the tongue on the left side and tongue deviation to the left on the protrusion. The upper aero-digestive tract endoscopic examination was negative for other lesions.

Fig. 1.

On admission, clinical examination showed the patient’s tongue atrophic and swollen on the left side with non-painful alteration on the dorsal tongue surface

A computed tomography(CT) scan revealed an extensive hypodense lesion, which affects the left hemitongue with no evidence of abnormal lymph nodes(Fig. 2). The magnetic resonance imaging(MRI) confirmed an area of T2 hyperintensity on the left side of the tongue.

Fig. 2.

CT (A) axial and (B) sagittal scan revealed an extended hypodense mass, which affects the left tongue with enlargement of the left tongue base (asterisk) and a calcified schwannoma in the proximity of the hypoglossal canal (arrow)

In both imaging, it results in an enlargement of the left tongue, with a demarcation of the signal alteration near its midline, which was suspicious for a neoplasm.

Due to the suspicion raised by the clinical and imaging findings, we conducted two biopsies: one on the ulcer-like lesion of the left tongue lateral margin and another on the left tongue base. However, the biopsies were negative for malignancy. Electromyography and nerve conduction studies confirmed the left-sided HNP diagnosis.

Then, both diagnostic imaging were re-evaluated and the radiologist noticed a small mass(1.97 mm) that appears as a dense area of increased radiopacity within the bone tissue, suspicious for schwannoma of the HN with massive calcification. It resulted in a small, oval-shaped mass growth not noticed before on instrumental imaging(Fig. 2). Therefore, the patient was clinically diagnosed as isolated HNP, likely resulting from calcified schwannoma of HN. Thus, the decision treatment involved a multidisciplinary team of specialists, including maxillofacial surgeons, neurosurgeons, and radiologists. Considering the tumor size, location, patient’s anamnestic history, overall health status, and potential risks and benefits of surgery, conservative management was considered.

Discussion

HN palsy can result and be related to various clinical conditions [1–3]. When suspected, CT or MRI may be performed to pinpoint its cause. In certain cases, HNP can mimic a tumor, as in our patient who was initially suspected of having a tongue tumor based on CT and MRI results. There are several possible explanations for why HNP can mimic a tumor. Nerve compression or injury can cause edema or inflammation in the surrounding tissue, which may appear as a mass on imaging studies. Additionally, the presence of HNP alters the tongue tropism, leading to volume loss of the affected muscles, fatty replacement, and tongue prolapse to the oropharynx, contributing to the appearance of a mass. Furthermore, the imaging findings on MRI of chronic HNP can lead to errors in diagnosis [4, 5]. The high signal intensity on T2 and abnormal enhancement can mimic a tumor [5].

Radiologists, especially if biased by a previous positive patient history of cancer and unfamiliar with tongue denervation imaging findings, may misinterpret them as a primary base of a tongue tumor [5]. This can lead to failure in identifying the underlying cause of tongue paralysis, prompting unnecessary investigations and interventions. An exhaustive workup is essential to prevent this. Thompson and Smoker [6] described an anatomical scheme for the imaging assessment of HN dysfunction based on the different pathological processes that may occur at different segments of this nerve. The course of the HN from the dorsal medulla along the skull base through the hypoglossal canal, in the carotid sheath to the sublingual space must be interrogated [5].

While hypoglossal schwannomas are a rare potential cause of HP, calcification and ossification in these tumors are even rarer [7]. Such findings can lead to diagnostic confusion with other mesenchymal tumors, which more frequently harbor these features. The role of the radiologist is paramount in accurately diagnosing tongue paralysis and its underlying causes. In our case, a failure to identify HPS led to extensive workups, including endoscopy and mucosal biopsies. The careful analysis of a CT scan of the affected tongue for the presence of fatty infiltration, and an abrupt linear demarcation of signal alterations could have oriented us for an HNP [5]. After the correct diagnosis of tongue denervation, an orderly search for pathologies that may account for HNP can follow.

Careful scrutiny of the entire HN course for pathology is mandatory; however, overlooked lesions are not uncommon. The intricate anatomy of the skull base and its position at the edge of radiological images often lead to the overlooking of skull base pathologies [5, 8]. In our case, imaging revealed an unusual very small solid cystic tumor with massive calcification proximally to the HN canal initially overlooked.

The treatment of schwannoma typically involves surgical resection, with the goal of preserving nerve function and achieving complete removal of the lesion [9]. However, the size and location of the tumor, the degree of nerve involvement, the patient’s age and overall health status, and the potential risks and benefits of surgery can influence decision-making. In some cases, conservative management may be considered. Indeed, HN schwannomas are typically slow-growing and benign tumors. Low-grade tumors may be managed with observation and periodic imaging [9]. In conclusion, calcified schwannoma is a rare cause of HNP. Clinicians should remain open-minded about atypical clinical presentations. Swelling and hemitongue weakness can indicate HN pathology. Vigilant search for skull base masses facilitates expedited diagnosis, even for rare calcified schwannomas.

AuthorContribution

Conceptualization:; Methodology: Paolo Gennaro, Valerio Ramieri, Lisa Catarzi, Formal analysis and investigation: Paolo Gennaro, Valerio Ramieri, Lisa Catarzi, Guido Gabriele; Writing - original draft preparation: Paolo Gennaro, Lisa Catarzi,; Writing - review and editing: Paolo Gennaro, Lisa Catarzi, Valerio Ramieri, Guido Gabriele; Supervision: Paolo Gennaro, Valerio Ramieri, Guido Gabriele, Lisa Catarzi.

Declarations

All procedures performed in studies involving human participants were in accordance with the ethical standards of the institutional and/or national research committee and with the 1964 Helsinki Declaration and its later amendments or comparable ethical standards.

Competing Interest and Funding

The authors have no competing interests to declare that are relevant to the content of this article. The authors did not receive support from any organization for the submitted work. The authors declare they have no financial interests.