A 28-year-old woman presents to the ED for sudden-onset double vision and gait instability that began 2 hours ago. Neurologic exam shows impaired adduction of the left eye on rightward gaze with abducting nystagmus of the right eye. Convergence is intact. She also has left-sided limb ataxia on finger-to-nose and heel-to-shin testing. Facial sensation to pinprick and temperature is normal bilaterally. Pain and temperature sensation in the trunk and extremities is normal. Which of the following additional findings is most likely if the lesion extends to involve a nearby midline brainstem structure per the “Rules of 4” organization of the brainstem (ventral view)?