Medial medullary syndrome, also known as inferior alternating syndrome, hypoglossal alternating hemiplegia, lower alternating hemiplegia, or Dejerine syndrome, is a type of alternating hemiplegia

Alternating hemiplegia

Alternating hemiplegia refers to a form of hemiplegia that has an ipsilateral and contralateral presentation in different parts of the body. The disorder is characterized by recurrent episodes of paralysis on one side of the body. This type of syndrome can result from a unilateral lesion in the...

 characterized by a set of clinical features resulting from occlusion of the anterior spinal artery

Anterior spinal artery

In human anatomy, the anterior spinal artery is the blood vessel that supplies the anterior portion of the spinal cord. It arises from branches of the vertebral arteries and is supplied by the anterior segmental medullary arteries, including the artery of Adamkiewicz, and courses along the anterior...

. This results in the infarction of medial part of the medulla oblongata

Medulla oblongata

The medulla oblongata is the lower half of the brainstem. In discussions of neurology and similar contexts where no ambiguity will result, it is often referred to as simply the medulla...

.

Pathophysiology

The infarction leads to death of the ipsilateral medullary pyramid, the medial leminiscus, and hypoglossal nerve

Hypoglossal nerve

The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal...

 fibers that pass through the medulla. The spinothalamic tract

Spinothalamic tract

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch...

 is spared because it is located more laterally in the brainstem and is not supplied by the anterior spinal artery, but rather by the vertebral

Vertebral artery

The vertebral arteries are major arteries of the neck. They branch from the subclavian arteries and merge to form the single midline basilar artery in a complex called the vertebrobasilar system, which supplies blood to the posterior part of the circle of Willis and thus significant portions of the...

 and posterior inferior cerebellar

Posterior inferior cerebellar artery

The posterior inferior cerebellar artery , the largest branch of the vertebral artery, is one of the three main arterial blood supplies for the cerebellum, part of the brain...

 arteries. The trigeminal nucleus is also spared, since most of it is higher up in the pons

Pons

The pons is a structure located on the brain stem, named after the Latin word for "bridge" or the 16th-century Italian anatomist and surgeon Costanzo Varolio . It is superior to the medulla oblongata, inferior to the midbrain, and ventral to the cerebellum. In humans and other bipeds this means it...

, and the spinal part of it found in the medulla is lateral to the infarct.

Presentation

The condition usually consists of:

Description	Source of damage	Number on diagram
a deviation of the tongue to the ipsilateral side of the infarct on attempted protrusion, caused by muscle weakness on the ipsilateral side	hypoglossal nerve Hypoglossal nerve The hypoglossal nerve is the twelfth cranial nerve , leading to the tongue. The nerve arises from the hypoglossal nucleus and emerges from the medulla oblongata in the preolivary sulcus separating the olive and the pyramid. It then passes through the hypoglossal canal...  fibers	#8
limb weakness (or hemiplegia Hemiplegia Hemiplegia /he.mə.pliː.dʒiə/ is total paralysis of the arm, leg, and trunk on the same side of the body. Hemiplegia is more severe than hemiparesis, wherein one half of the body has less marked weakness.... , depending on severity), on the contralateral side of the infarct	medullary pyramid and hence to the corticospinal fibers of the pyramidal tract	#5
a loss of discriminative touch, conscious proprioception Proprioception Proprioception , from Latin proprius, meaning "one's own" and perception, is the sense of the relative position of neighbouring parts of the body and strength of effort being employed in movement... , and vibration sense on the contralateral side of the infarct	medial leminiscus	#6

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

Spinothalamic tract

The spinothalamic tract is a sensory pathway originating in the spinal cord. It transmits information to the thalamus about pain, temperature, itch and crude touch...

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).

External links

• http://isc.temple.edu/neuroanatomy/lab/lesions/14.htm
• http://www.neuropat.dote.hu/table/kereszt7.htm