Isolated hemifacial sensory impairment with onion skin distribution caused by small pontine hemorrhage.

minute and regular. Neurological examinations revealed an alert and well-oriented woman with isolated tactile sensory impairment over the right trigeminal distribution including the oral cavity. Pain and temperature sensations were not impaired. The hypesthesia showed so-called onion skin distribution and was least intense in the perioral and perinasal areas and most prominent in the most peripheral parts of the face, such as the forehead and chin. Corneal sensation and corneal reflex were well preserved. No weakness of the masseteric muscle or jaw deviation was observed. Taste sensation was normal. There was no abnormality in cranial nerves, coordination or body sensation, except for the face. Brain CT performed on admission and 1.5 h after onset demonstrated a small, high-density area at the right pontine tegmentum ( fig. 1 ). The diameter of the hematoma was less than 1 cm and did not enlarge on a second CT performed 6 h after onset. T 1 -weighted MRI on the seventh day showed a column-shaped hematoma in areas extending from the middle part to the lower portion of the pons and accompanied by a smaller sublesion ( fig. 2 A–C). The hematoma did not reach the medulla oblongata, as confirmed by coronal MRI. MR angiography on the seventh day disclosed no abnormality suggestive of arteriovenous malformation, aneurysm or Dear Sir, Isolated trigeminal sensory neuropathy due to pontine hemorrhage has only been found in a few previous cases [1–4] . In these, the hemorrhage affected either the principal sensory nucleus [1, 2] or the trigeminal nerve roots [3, 4] and produced facial sensory impairments along the ophthalmic (V1), maxillary (V2) and/or mandibular (V3) nerve dermatome. We report a patient with a small pontine hemorrhage that affected the upper part of the spinal trigeminal nuclei, mainly the nucleus oralis and interpolaris. She developed isolated facial tactile sensory impairment with ‘onion skin’ distribution in the absence of other neurological deficits. Onion skin type facial sensory impairment caused by these upper spinal trigeminal nuclei due to stroke has never been previously reported.