1) VASCULAR LESIONS - LATERAL MEDULLARY SYNDROME (OF WALLENBERG)
A Sample Case: A 50 year old woman had a sudden onset of dizziness and vomiting. Her family noticed that her left eyelid appeared to be drooping and she was taken to see a doctor.
The neurologic exam demonstrated loss of pain and temperature sensation from her right side of the body but there was numbness on the left side of her face. Though there was normal proprioception and vibratory sensation bilaterally she still had an ataxic gait with falling toward the left side. There was no indication of spastic paralysis or Babinski signs. When she spoke her voice had a hoarse quality and she had a diminished gag reflex.
Dizziness and vomiting suggest a lesion above the spinal cord. Spinothalamic tract involvement on the left side is indicated by the loss of pain and temperature sensation from the right side of the body. Numbness of the face on the right is consistent with injury to the nucleus and tract of spinal V on the right side (which lies near the spinothalamic tracts). Hoarseness and an abnormal gag reflex indicates that the level of the lesion is that of CN IX and X. Normal proprioception and motor strength indicates intact medial lemniscus and pyramidal tracts; the ataxic gait is probably a "cerebellar" sign attributable to injury of the inferior cerebellar peduncle (which lies near the tract of spinal V and the spinothalamics).
Dizziness and vomiting may be due to involvement of the vestibular nuclei and/or CN X. Drooping of the right eyelid is part of the Horner's syndrome; at this level it is due to injury of the descending autonomics in the reticular formation.
The anatomic distribution of the involved structures indicates that the injury has occurred within the area of distribution of the posterior inferior cerebellar artery. Due to infarction, this is the most common medullary syndrome.