A tardy tongue palsy

Abstract

A 76-year-old man presented with insidious onset of slurred speech and difficulty swallowing over 1 year. Initial symptoms were episodic imprecise articulation, tongue swelling, tongue deviation, and mild right-sided headache. Progressive deterioration of speech and swallowing function had occurred; at the time of presentation, the patient was struggling to swallow food and saliva. He had undergone C1-C5 posterior fusion following a C2 fracture 50 years prior. There was no relevant medical history and the patient was systemically well. Examination found hemiatrophy of the right side of the tongue with visible fasciculations. The tongue protruded to the right and there was associated dysarthria. There was no evidence of other cranial nerve involvement, cervical myelopathy, or a diffuse motor neuron disorder.Imaging of the head found evidence of right atlanto-occipital arthritis with an osteophyte impinging upon the right exiting hypoglossal nerve at the hypoglossal canal. The right genioglossus was denervated and atrophic (figure). Vascular imaging excluded dissection of cervical or intracranial vessels. Needle EMG of the tongue found fibrillations and small, polyphasic varying motor units with markedly reduced recruitment in the right genioglossus, suggesting active denervation and reinnervation. EMG of left genioglossus and upper and lower limbs was unremarkable.Extension of the cervical fusion was considered, but the patient elected to pursue conservative treatment and underwent a course of speech therapy. DISCUSSIONThe twelfth cranial nerve is a pure motor nerve primarily responsible for innervation of the intrinsic and extrinsic muscles of the tongue. Nerve injury causes speech and swallowing dysfunction, ipsilateral tongue paresis, and deviation to the side of the lesion. Hypoglossal nerve lesions are rare and result from diverse etiologies, most commonly benign or malignant tumors, trauma, stroke, vascular dissection, brainstem demyelination, infection, and iatrogenic injury. 1In this case, the hypoglossal neuropathy most likely resulted from mechanical compromise of the nerve by an osteophyte arising from the right atlanto-occipital joint. There is heterotopic ossification outside of the hypoglossal canal; therefore direct nerve impingement is likely responsible for ongoing denervation. Arthritis of this joint typically presents with unilateral unremitting occipital-cervical pain exacerbated by neck movement and neurologic complications are rare. However, dynamic motion between the occipital cervical junction may also contribute to nerve injury. The history of trauma is relevant, since post-traumatic arthritis of the joint, or arthritis secondary to cervical spine fixation (i.e., adjacent segment disease), may be contributory. The long delay between the original neck injury and the onset of tongue weakness Practical ImplicationsHypoglossal neuropathy is a rare complication of neck trauma and degenerative spine disease. Atlanto-occipital arthritis should be considered as a possible cause for isolated hypog...