Focal pseudohypertrophy of the left hemi-tongue

Abstract

A 72 year-old man with a history of diabetes mellitus noticed that his tongue deviated to the left when it was stuck out. He consulted our hospital since this feature persisted for 9 months. The diabetes mellitus was well controlled by voglibose (0.6 mg/day) and gliclazide (80 mg/day), and serum levels of glucose and glycated hemoglobin were 104 mg/dl and 6.1%, respectively. The patient had no signs of neurologic involvement attributable to diabetes mellitus. The left side of the tongue was hypertrophic and the tongue deviated to left (Fig. 1). Left hemi-tongue weakness was evident. There was no fasciculation, and deep tendon reflexes were normal, with no pathological reflexes. The results of other neurological examinations including swallowing, speaking and tasting were negative. Electromyography of the left side of the tongue showed neuropathic motor unit action potentials, polyphasic motor unit potentials, positive sharp wave and fibrillation potentials. The number of motor units per second was decreased. The right side of the tongue showed none of these findings. All other muscles examined (deltoid, biceps, triceps, adductor of thumb, quadriceps, gastrocnemius, and tibialis anterior) showed no evidence of neuropathic or myopathic motor unit action potentials. Magnetic resonance imaging (MRI) of the tongue revealed markedly increased signal intensity in the left side of the tongue on T1-weighted images (Fig. 1a, c) and T2weighted images (Fig. 1b). The left side of the tongue was enlarged. Contrast-enhanced, T1-weighted MRI images obtained with the use of a bolus of gadoliniumdiethylenetriamine pentaacetic acid showed a circular lesion with ringed enhancement in the root of the left side of the tongue (Fig. 1d, white arrow). Intracranial abnormal signals including the brainstem were not evident on MRI. Anti-IL2 receptor antibody (303 U/ml), antinuclear antibody, and M-protein on immunoelectrophoresis were negative. Hypertrophy of the root of the left side of the tongue was evident on laryngoscopy. A biopsy of the root of the tongue showed lymphocyte infiltration with no malignant cells. Monoclonality was absent on immunohistochemical studies. One year later, short inversion time inversion recovery (STIR) images on repeated MRI showed the decreased signal intensity in the left hemitongue with increased signal intensity on T1-weighted images and T2-weighted images. The size of the circular lesion with ringed enhancement was unchanged. On the basis of the ringed enhancement on MRI and the presence of lymphocyte infiltration with no malignancy on histopathological examination, the lesion was diagnosed to be an inflammatory cystic lesion ‘‘abscess’’. On 20 months after consultation to our hospital, the left hemi-tongue weakness was static. These findings could be explained by denervation and reinnervation or by increasing frequencies of motor unit firing from the left hypoglossal nerve and adjacent motor fibers, which were impaired by the cystic lesion in the left side of the tongue. Neuralgic muscle hypertrophy of the limbs has been reported in several types of lower motor neuron disease, such as multifocal motor neuropathy [1], Guillain-Barre syndrome [1], and radiculopathy [3, 4], but such hypertrophy involving cranial nerves has not been reported previously to our knowledge. Prior studies suggest that continuous, spontaneous electrical activity of a muscle associated with disease conditions can cause neuralgic H. Kataoka (&) S. Ueno Department of Neurology, Nara Medical University, 840 Shijo-cho, Kashihara, Nara 634-8522, Japan e-mail: hk55@naramed-u.ac.jp