Case Report: Tongue deviation due to supranuclear injury with a rare semiological feature

Introduction

Understanding the diverse causes of hypoglossal nerve palsy, which can range from tumors and trauma to ischemia and demyelinating lesions, is crucial. These lesions can be categorized based on their location as infranuclear, nuclear, and supranuclear, providing a fundamental framework for further study and clinical practice.^1,2

Infranuclear lesions, a rare occurrence, directly affect the hypoglossal nerve before it exits the medulla oblongata. On the other hand, nuclear lesions involve the motor nuclei of the hypoglossal nerve in the medulla oblongata. Isolated lesions at the nuclear level are uncommon and usually accompanied by lesions in other nearby cranial nerves due to their position in the brainstem and posterior course. These lesions cause a deviation of the tongue towards the opposite side of the affected one due to the predominant contraction of the healthy half of the tongue.^3,4 Furthermore, they are usually associated with lower motor neuron signs such as atrophy and fasciculations.¹

Supranuclear lesions, which occur in higher areas such as the cerebral cortex, corticobulbar tract, cerebellar peduncles, and pons, are a distinct category. In the case of tongue control, the lower and lateral part of the precentral gyrus, in the primary motor area, plays a significant role. Corticobulbar fibers originate from this area and provide bilateral innervation to the hypoglossal nuclei, except for the nuclei portion that innervates the genioglossus muscle, which only receives innervation from the contralateral cortex. This characteristic explains why supranuclear lesions are often silent, as the cortical hypoglossal fibers of the contralateral cortex to the lesion remain intact. The body's remarkable ability to adapt and compensate for such lesions results in a mild weakness of the tongue muscles, which, in most cases, may not be evident.^5–7

Case report

We present the case of a 43-year-old male patient from Cartagena, Colombia, a right-handed motorcycle driver with a history of left distal radius fracture that required surgical management. The patient has no known cardiovascular history. He was referred from a primary care center due to a 6-hour clinical picture, which began upon awakening, consisting of dysarthria and deviation of the labial commissure to the left side. On admission, an electrocardiogram was performed, showing atrial fibrillation and elevated blood glucose levels.

On physical examination, he was found to be tachycardic, with normal oxygen saturation and blood pressure. The auscultation showed arrhythmic heart sounds, and the rest of the general physical examination was without significant alterations. On neurological examination, the patient was alert and dysarthric; however, fluent, understood, named, and repeated, with preserved orientation. There was evidence of left central facial paralysis (Figure 1) and tongue deviation to the left (Figure 2). Left upper limb mono paresis 4/5 on muscle strength scale, with distal predominance at regional evaluation. Reflexes were symmetrical with normal gait and coordination. Complementary studies showed average blood cell count, moderate hypokalemia, persistently elevated blood glucose levels, and urinalysis with glycosuria and preserved renal function. Atrial fibrillation on electrocardiogram. Based on these findings, it was considered an acute stroke of probable cardioembolic etiology, which is confirmed with brain MRI that evidenced right frontal cortico subcortical lacunar image with gliosis in T2 and FLAIR sequence and that restrings in diffusion (Figure 3).

Figure 1. Centra facial palsy on the left side of the face.

Figure 2. The left side of the tongue shows an important paralysis.

Figure 3. MRI axial brain T2 FLAIR (a) and Diffusion (b) shows an ischemic lesion with hemorrhagic changes.

The echocardiogram reported mitral valve prolapse, mild insufficiency, and normal biventricular systolic diastolic function with preserved ejection fraction. Carotid ultrasound reported no alterations and 24-hour holter monitoring with basal atrial fibrillation rhythm with variable ventricular response throughout the study. Diagnosis of ischemic stroke of cardioembolic etiology was made, first-diagnosis atrial fibrillation o with rapid ventricular response CHA2DS2-VASc 1 and HAS-BLED 1 and de novo type 2 diabetes mellitus. At discharge, he continued antiarrhythmic treatment and insulin therapy with oral antidiabetic and direct oral anticoagulant.

Discussion

The hypoglossal nerve nucleus is located in the tegmentum of the medulla oblongata, located between the midline and the dorsal motor nucleus of the vagus nerve. This thin-structured nucleus receives innervation from the precentral gyrus and is fed information from the inferior frontal cortex and the premotor cortex.⁶ This information is transmitted through corticobulbar tracts and distributed bilaterally to the hypoglossal nerve nuclei, resulting in unilateral lesions with a clinically insignificant effect.

A study involving 300 patients with unilateral cerebral infarctions showed that 29% of them had tongue deviation towards the side of the motor deficit. Most of these cases were associated with ipsilateral face and arm weakness. It was found that a lesion in the precentral gyrus in the tongue area could cause a contralateral palsy of the hypoglossal nerve, a phenomenon known as “pseudoperipheral tongue palsy.” In this type of situation, the tongue deviated towards the opposite side of the lesion, but atrophy or fasciculations were not observed, as took place in the present case.⁸

Disruption of the cortical lingual pathway plays a crucial role in developing dysarthria after cerebrovascular events due to the presence of a central mono paresis of the tongue.^9,10

Supranuclear paralyzes of the hypoglossal nerve of vascular origin, which cause tongue deviation, tend to be accompanied by other signs such as hemiparesis or, less frequently, weakness in the facial, pharyngeal, or masticatory musculature of the same side. These presentations set up an opercular syndrome on the affected side.¹¹ However, in our case, the presentation was atypical since a tongue deviation and facial weakness were observed, without marked hemiparesis, in the context of a unilateral supranuclear lesion.

Consent

We obtained written informed consent for publication of their clinical details and clinical images from the participants.