Unilateral Tongue Atrophy and Fasciculation

An otherwise healthy 42-year-old woman was involved in a minor motor vehicle crash and taken to a local hospital. On examination, she had right-sided tongue atrophy with visible fasciculations (Figure, A; video). On protrusion, the tongue deviated toward the right. There was no facial weakness, facial sensory impairment, or dysarthria, and the palate elevated symmetrically. There was no weakness of the sternocleidomastoid or trapezius muscles.

Magnetic resonance imaging of the head demonstrated an extra-axial homogeneously enhancing mass compressing the medulla and pons (Figure, B). The tumor was partially resected. Histological examination revealed a meningotheliomatous pattern with numerous psammoma bodies (Figure, C). Mitoses and necrosis were not present, and the proliferative index was estimated at 2% to 3%. Immunohistochemical staining of the tissue demonstrated expression of epithelial membrane antigen and no expression of S-100 protein. This histopathology is consistent with a meningioma, World Health Organization (WHO) grade I. As the resection was less than total, she also underwent stereotactic radiosurgical treatment with gamma knife.

Isolated unilateral lower motor neuron signs in the tongue include fasciculations, hemiatrophy, and fatty replacement. These signs should raise suspicion for a compressive injury of the hypoglossal nerve. Meningioma causing isolated hypoglossal nerve palsy is exceedingly rare but should be considered in the differential diagnosis.¹

Meningiomas are slowly growing tumors derived from meningoepithelial cells. They are classified according to the WHO system, which is based on morphologic criteria.² Most meningiomas are WHO grade I, which indicates that they enlarge slowly and do not infiltrate the brain parenchyma. Atypical meningiomas (WHO grade II) have increased mitotic figures and cellularity, and anaplastic meningiomas (WHO grade III) have loss of typical tumor architecture and can be infiltrative.

In cases of isolated hypoglossal nerve injury, schwannomas, metastatic tumors, trauma, and vascular causes should also be considered.^{3 - 4} Immunohistochemical staining can be used to differentiate meningiomas from other types of tumors and lesions. Epithelial membrane antigen staining is positive in tissue derived from mesoderm such as meningoepithelium and is relatively specific for meningioma, while S-100 protein stains tissue derived from neuroectoderm such as glial cells.

Neurologic imaging should be performed in all cases of suspected hypoglossal nerve injury to detect otherwise occult intracranial mass lesions. If a tumor is found, biopsy or surgical resection is necessary for definitive diagnosis. In cases of meningioma, determining the grade of the tumor is essential for appropriate treatment and is correlated with prognosis.