Ipsilateral Facial Tactile Hypesthesia in a Patient with Lateral Medullary Syndrome

Background: Various sensory impairments have been reported in patients with lateral medullary syndrome, also known as Wallenberg syndrome. The typical sensory impairments experienced by patients with this condition are ipsilateral facial and contralateral trunk and limb thermal hypesthesia and hypoalgesia. Tactile (light touch) sensation is not generally diminished. Here we report the case of a 35-year-old man with lateral medullary infarction who had atypical sensory impairment. Methods: We examined the results from the neurological examination of the patient as well as findings from computed tomography of the head and magnetic resonance imaging. Results: Magnetic resonance imaging showed left lateral medullary infarction caused by left posterior inferior cerebellar artery dissection. Neurological examination revealed both tactile and thermal/pain hypesthesia on the left side of the patient's face, and thermal/pain hypesthesia on his right upper and lower limbs. Conclusion: There are two types of tactile sensation: epicritic and protopathic. Facial tactile sensation is usually thought to be associated with epicritic tactile sensation, which travels through principal sensory nuclei of the trigeminal nerve. The protopathic pathway travels down through the spinal tract via the trigeminal nerve and is not considered a primary pathway. However, in this case the protopathic tactile sensation pathway might be involved, and it caused facial tactile hypesthesia. Because most of previous case reports and literature reviews focused only on thermal/pain hypesthesia, we believe that this case provides critical information on the brainstem neuroanatomy, especially for the protopathic tactile sensation pathway in patients with stroke.