Medial medullary syndrome, also known as inferior alternating syndrome, hypoglossal alternating hemiplegia, lower alternating hemiplegia, or Dejerine syndrome, is a type of alternating hemiplegia characterized by a set of clinical features resulting from occlusion of the

anterior spinal artery In human anatomy, the anterior spinal artery is the artery that supplies the anterior portion of the spinal cord. It arises from branches of the vertebral arteries and courses along the anterior aspect of the spinal cord. It is reinforced by sever ...

. This results in the infarction of medial part of the

medulla oblongata The medulla oblongata or simply medulla is a long stem-like structure which makes up the lower part of the brainstem. It is anterior and partially inferior to the cerebellum. It is a cone-shaped neuronal mass responsible for autonomic (invol ...

Presentation

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 The spinothalamic tract is a part of the anterolateral system or the ventrolateral system, a sensory pathway to the thalamus. From the ventral posterolateral nucleus in the thalamus, sensory information is relayed upward to the somatosensory co ...

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).

Pathophysiology

The anterior spinal artery arises bilaterally as two small branches near the termination of the vertebral arteries which descend anterior to the medulla and unite at the level of the foramen magnum. The infarction (which arises in the paramedian branches of the anterior spinal artery and/or the vertebral arteries) leads to death of the ipsilateral medullary pyramid, the

medial lemniscus In neuroanatomy, the medial lemniscus, also known as Reil's band or Reil's ribbon (for German anatomist Johann Christian Reil), is a large ascending bundle of heavily myelinated axons that decussate (cross) in the brainstem, specifically in the ...

, and the

hypoglossal nerve The hypoglossal nerve, also known as the twelfth cranial nerve, cranial nerve XII, or simply CN XII, is a cranial nerve that innervates all the extrinsic and intrinsic muscles of the tongue except for the palatoglossus, which is innervated ...

fibers that pass through the medulla. The

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 The vertebral column, also known as the backbone or spine, is part of the axial skeleton. The vertebral column is the defining characteristic of a vertebrate in which the notochord (a flexible rod of uniform composition) found in all chordates ...

and posterior inferior cerebellar arteries. The trigeminal nucleus is also spared, since most of it is higher up in the

pons The pons (from Latin , "bridge") is part of the brainstem that in humans and other bipeds lies inferior to the midbrain, superior to the medulla oblongata and anterior to the cerebellum. The pons is also called the pons Varolii ("bridge of Va ...

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

Diagnosis

Ipsilateral signs and symptoms - flaccid paralysis (lmn) paralysis and atrophy of one half of tongue (hypoglossal nerve) Contralateral signs and symptoms-spastic (umn) paralysis of trunk and limbs (contralateral corticospinal tract) Impaired tactile, proprioceptive and vibration sense of trunk and limbs (contralateral medial lemniscus)

Management

References

External links