Crossed paresis is mainly seen in injuries to one side of the brainstem, such as brainstem infarction, brainstem hemorrhage, brainstem trauma, or brainstem tumors. Injury to the descending pyramidal tract fibers in one side of the brainstem may result in symptoms such as contralateral limb paresis and contralateral tongue paresis. Injury to the motor nucleus fibers of the locomotor nerve, talocrural nerve, adductor nerve, facial nerve and trigeminal nerve on the ipsilateral side of the brainstem may result in symptoms such as ipsilateral eye movement disorder, ipsilateral peripheral facial palsy and ipsilateral masticatory muscle weakness. In addition, if the suspected nucleus is damaged, ipsilateral pharyngeal muscle paralysis may also occur, manifesting symptoms such as dysphagia and choking on water, which is called crossed paralysis.