Idiopathic Isolated Unilateral Hypoglossal Nerve Palsy: A Report of 2 Cases and Review of the Literature

Hypoglossal nerve palsy (HNP) is a common finding in neurologic diseases when associated with other cranial nerve palsies or further pathology and exhibits characteristic clinical manifestations, including unilateral atrophy of the musculature of the tongue. It occasionally appears as the initial or solitary sign of an intracranial or extracranial space-occupying lesion, head or neck injury, or vascular abnormality of the internal carotid artery. There are few cases of idiopathic isolated unilateral HNP, which should be diagnosed through exclusion. This report describes 2 patients who had different outcomes and presents a literature review of idiopathic isolated unilateral HNP. Case 1 was a 71-year-old man who was referred with a 1-month history of dysphagia and speech impairment. Intraoral examination disclosed marked left-side hemiatrophy of the tongue and deviation toward the left on protrusion. At coronal Tl-weighted magnetic resonance imaging, left-side hemiatrophy of the tongue was clearly visible through deviation of the median septum to the left. The patient was diagnosed with idiopathic isolated unilateral HNP through exclusion and was treated with steroids and mecobalamin, but he did not recover. Case 2 was a 32-year-old man complaining of tongue weakness for 2 days. On examination, left HNP was evident, with deviation of the tongue to the left on protrusion. He was diagnosed with idiopathic isolated unilateral HNP through exclusion and was treated with steroids. After 3 weeks, the patient had completely recovered. To the best of the authors' knowledge, this is the first detailed literature review on idiopathic isolated unilateral HNP. This condition is very rare but should be considered for diagnosis. It warrants a thorough and stepwise approach for etiologic diagnosis.