Isolated Hypoglossal Nerve Palsy as an Early Symptom of a Granular Cell Tumor

Background: Hypoglossal nerve palsy (HNP) is rather common as a neurological disease. However, as an isolated nerve palsy it is an exceedingly rare phenomenon and points at local pathologies along the peripheral course of the nerve. In this communication we report a granular cell tumor (GCT) arising in the submandibular segment of the hypoglossal nerve. Case-Report: Spontaneous isolated HNP was recognized in a female patient. First line MR-imaging identified a clivus-chordoma. However, involvement of the hypoglossal nerve was highly unlikely according to MR-findings. Finally, ultrasonographic investigation revealed a small submandibular mass which, at histological examination, turned out to be a granular cell tumor arising within the hypoglossal nerve. Conclusions: This is the report of an extremely rare GCT originating within the 12th cranial nerve. The case illustrates that isolated motoric cranial nerve palsy may result from this rare tumor entity. This report also points out the diagnostic value of a simple ultrasonographic investigation to depict pathologic lesions of the submandibular space.