{{Infobox ICD
| BREITE = 
| 01-CODE = A46.3
| 01-BEZEICHNUNG = '''Hirnstammsyndrom''' </br>Wallenberg-Syndrom
}}
Das '''Wallenberg-Syndrom''' (auch: '''Dorsolaterales Medulla-oblongata-Syndrom''') ist eine besondere Form des Schlaganfalls, bei der ein Infarkt in einem bestimmten Bereich des Hirnstamms stattfindet. Es trägt seinen Namen nach dem deutschen Neurologen Adolf Wallenberg.

thumb|Infarkt in der dorsolateralen Medulla oblongata links, auf dieser diffusionsgewichteten [[Magnetresonanztomographie|MRT-Aufnahme als heller Fleck erkennbar]]
Ursache dieses Infarkts ist ein Verschluss im Bereich der hinteren unteren Kleinhirnarterie (''Arteria cerebelli inferior posterior'', engl. Abkürzung PICA), die Teile des verlängerten Marks (Medulla oblongata) versorgt. Gelegentlich liegt auch ein Verschluss im Bereich der Arteria vertebralis vor.

Durch die Sauerstoffunterversorgung werden Strukturen im hinteren seitlichen (dorsolateralen) Teil der Medulla oblongata geschädigt. Zu diesen gehören im einzelnen:

*Nucleus dorsalis nervi vagi
*Nucleus ambiguus
*Nucleus tractus spinalis nervi trigemini
*Nucleus tractus solitarii
*Nucleus vestibularis inferior
*Tractus spinocerebellaris anterior
*Tractus spinothalamicus lateralis
*Tractus tegmentalis centralis
*Formatio reticularis
*zentrale Sympathicusbahn

{{Infobox_Disease |
  Name           =  |
  Image          = CerebellumArteries.jpg  |
  Caption        = The three major arteries of the cerebellum: the SCA, AICA, and PICA. (Posterior inferior cerebellar artery is PICA.) |
  DiseasesDB     = 10449 |
  ICD10          =  |
  ICD9           = |
  ICDO           = |
  OMIM           = |
  MedlinePlus    = |
  eMedicineSubj  = emerg |
  eMedicineTopic = 834 |
  MeshID         = D014854 |
}}
'''Lateral medullary syndrome''' (also called '''Wallenberg's syndrome''' and '''posterior inferior cerebellar artery syndrome''') is a disease in which the patient has difficulty with swallowing or speaking or both owing to one or more patches of dead tissue (known as an ''infarct'') caused by interrupted blood supply to parts of the brain.

==Cause==
It is the clinical manifestation resulting from occlusion of the posterior inferior cerebellar artery (PICA) or one of its branches or of the vertebral artery, in which the lateral part of the medulla oblongata infarcts, resulting in a typical pattern.

== Clinical features ==

Lateral medullary syndrome presents with the following symptoms:

{| class="wikitable"
| '''Dysfunction''' || '''Effects''' 
 |- 
 | | [[contralateral deficits in pain and temperature sensation from body
 |- 
 | | [[ipsilateral loss of pain and temperature sensation from face
 |- 
 |  vagus X and glossopharyngeal nerves IX) || dysphagia, hoarseness, diminished gag reflex
 |- 
 | | [[vertigo (medical)|vertigo, diplopia, nystagmus, vomiting
 |- 
 | descending | ipsilateral [[Horner's syndrome
 |-
 | | [[palatal myoclonus
|}

An affected person may present with ataxia on the side of lesion. Hiccups are another common sign.

==Presentation==
This syndrome is characterized by sensory deficits affecting the trunk and extremities on the opposite side of the infarct and sensory and motor deficits affecting the face and cranial nerves on the same side with the infarct. Other clinical symptoms and findings are vertigo, nystagmus, Horner's syndrome, diplopia and dysphagia. The cause of this syndrome is usually the occlusion of the posterior inferior cerebellar artery (PICA) at its origin.

The affected persons have difficulty in swallowing (dysphagia) resulting from involvement of the nucleus ambiguus, and slurred speech (dysphonia, dysarthria). Damage to the spinal trigeminal nucleus causes absence of pain on the ipsilateral side of the face, as well as an absent corneal reflex.

The spinothalamic tract is damaged, resulting in loss of pain and temperature sensation to the opposite side of the body. The damage to the cerebellum or the inferior cerebellar peduncle can cause ataxia.

Nystagmus and vertigo, which may result in falling, caused from involvement of the region of Deiters' nucleus and other vestibular nuclei.