The condition usually consists of:
Sensation to the face is preserved, due to the sparing of the trigeminal nucleus.

The syndrome is said to be "alternating" because the lesion causes symptoms both contralaterally and ipsilaterally.
Sensation of pain and temperature is preserved, because the spinothalamic tract is located more laterally in the brainstem and is also not supplied by the anterior spinal artery (instead supplied by the posterior inferior cerebellar arteries and the vertebral arteries).
The condition usually consists of:
Sensation to the face is preserved, due to the sparing of the trigeminal nucleus.
The syndrome is said to be "alternating" because the lesion causes symptoms both contralaterally and ipsilaterally. Sensation of pain and temperature is preserved, because the spinothalamic tract is located more laterally in the brainstem and is also not supplied by the anterior spinal artery (instead supplied by the posterior inferior cerebellar arteries and the vertebral arteries).
Medial medullary syndrome