A 56-year-old man is brought to the emergency department due to severe dizziness and difficulty walking since this morning. He also reports a sharp, stabbing pain on the left side of his face. The patient has had no tinnitus or hearing loss, and medical history includes type 2 diabetes mellitus and hypertension. Blood pressure is 144/90 mm Hg and pulse is 92/min. On physical examination, there is mild left-sided ptosis, and the left pupil is smaller than the right, but both pupils react briskly to light. Horizontal and rotational nystagmus is present. Sensation to pain and temperature is decreased on the left side of the face and the right trunk and limbs. On standing, the patient has a wide base and falls to the right if unsupported. He is unable to walk without assistance. Which of the following is the most likely location of this patient's brain lesion?

Question

A 56-year-old man is brought to the emergency department due to severe dizziness and difficulty walking since this morning.  He also reports a sharp, stabbing pain on the left side of his face.  The patient has had no tinnitus or hearing loss, and medical history includes type 2 diabetes mellitus and hypertension.  Blood pressure is 144/90 mm Hg and pulse is 92/min.  On physical examination, there is mild left-sided ptosis, and the left pupil is smaller than the right, but both pupils react briskly to light.  Horizontal and rotational nystagmus is present.  Sensation to pain and temperature is decreased on the left side of the face and the right trunk and limbs.  On standing, the patient has a wide base and falls to the right if unsupported.  He is unable to walk without assistance.  Which of the following is the most likely location of this patient's brain lesion?

Quizplus · Accepted Answer

Explanation: 11ec25c8_d5af_fd05_bc81_dbc47af2af47_MD0003_00 This patient's stroke has resulted in vertigo, ataxia, and Horner syndrome, in addition to loss of pain and temperature sensation on the left side of the face and right side of the body (eg, trunk, limbs). Because the brainstem is where most cranial nerves originate and many motor and sensory fibers cross the midline, brainstem strokes characteristically lead to ipsilateral cranial nerve deficits and contralateral deficits of the body (ie, crossed signs). Therefore, this patient's stroke likely impacted the left side of the brainstem. In addition, he has the following: Vertigo without hearing loss, suggesting a lesion impacting the vestibular nucleus rather than the peripheral CN VIII (which would likely result in hearing loss as well). Loss of pain and temperature on the left side (ipsilateral) of the face, with neuropathic pain suggesting involvement of the spinal trigeminal nucleus Loss of sensation on the right (contralateral) side of the body, which suggests dysfunction of the spinothalamic tract Horner syndrome, which may occur due to damage of the descending sympathetic nervous system fibers that travel very close to the spinothalamic tract These areas are all located in the lateral medulla. This constellation of symptoms is consistent with lateral medullary (Wallenberg) syndrome. (Choice A) Although a stroke impacting the cerebellum would present with dizziness and ataxia, it would not usually cause Horner syndrome or loss of pain and temperature sensation. (Choices C and E) Strokes in the midbrain can lead to ataxia due to dysfunction of the red nucleus. However, patients typically have an ipsilateral oculomotor (CN III) palsy and contralateral hemiparesis (corticospinal tract). Such strokes would not cause loss of pain and temperature sensation or Horner syndrome. (Choice D) A lesion in the right medulla would lead to the loss of pain and temperature sensation on the right side of the face and left side of the body; Horner syndrome would be on the right. Educational objective: A lateral medullary infarct (Wallenberg syndrome) leads to vertigo/nystagmus (vestibular nucleus), loss of pain/temperature sensation on the ipsilateral face (trigeminal nucleus) and contralateral body (spinothalamic tract), bulbar weakness (lower cranial nerves), and ipsilateral Horner syndrome (descending sympathetic). References: Traumatic vertebral artery dissection and Wallenberg syndrome after a motorcycle collision. (http://www.ncbi.nlm.nih.gov/pubmed/19041559) Dysphagia caused by a lateral medullary infarction syndrome (Wallenberg's syndrome). (http://www.ncbi.nlm.nih.gov/pubmed/23077713)

A 56-Year-Old Man Is Brought to the Emergency Department Due