Medial medullary syndrome

Medial medullary syndrome (also known as Dejerine syndrome, after Joseph Jules Dejerine) is a set of clinical features resulting from an infarction in the brainstem. The vessel usually involved is the anterior spinal artery which supplies the medial part of the medulla oblongata.

It is also known as "inferior alternating syndrome", or "hypoglossal alternating hemiplegia".

It should not be confused with alexia without agraphia, an unrelated condition which is also sometimes called "Dejerine syndrome".

Presentation
The condition usually consists of:
 * a weakened tongue on the affected side of the brainstem (due to involvement of the hypoglossal nerve root).
 * weakness of the limbs on the contralateral (opposite) side (caused by pyramidal tract damage).
 * a loss discriminative sensation on the contralateral side (from medial lemniscus involvement).

Sensation of pain and temperature from the body is preserved, as this travels up the spinothalamic tract which is more lateral in this part of the brainstem, and supplied by the vertebral or the posterior inferior cerebellar artery. Sensation on the face is usually intact, as this travels mostly by the trigeminal nucleus; most of this nucleus is higher up in the pons, and the spinal part (responsible for pain sensation) is lateral to the infarct. It is in the corticospinal tract.