Arteries of Posterior Cranial Fossa


Lateral Medullary Syndrome


Atherosclerosis of the intracranial vertebral arteries is most severe in the distal portion of the arteries, often at the vertebral-basilar artery junction, sometimes extending into the proximal basilar artery. Stenosis is also common just after dural penetration. Most often, patients with proximal intracranial vertebral artery occlusive disease present with features of the lateral medullary syndrome. The findings are understood best by reviewing the structures in the lateral medullary tegmentum that are specifically involved.


1. Nucleus and descending spinal tract of V. Sharp jabs of pain are found in the ipsilateral eye and face, and numbness of the face; examination confirms decreased pinprick and temperature sensations on the ipsilateral face.


2. Vestibular nuclei and their connections. Feelings of dizziness or instability of the environment may be present; examination shows nystagmus with coarse rotatory eye movements when looking to the ipsilateral side and small-amplitude faster nystagmus when looking contralaterally.


3. Spinothalamic tract. There is decreased pinprick and temperature sensation in the contralateral limbs and body; a sensory level may be present on the contralateral trunk with pain and temperature loss on the trunk below that level and in the lower extremity. The pinprick and temperature loss can extend to the contralateral face when the crossed quintothalamic tract that appends itself medially to the spinothalamic tract is involved. Rarely, the loss of pain and temperature sensation is totally contralateral and involves the face, arm, trunk, and leg.


4. Inferior cerebellar peduncle. There is veering or leaning toward the side of the lesion and clumsiness of the ipsilateral limbs; examination shows hypotonia and exaggerated rebound of the ipsilateral arm. On standing or sitting, patients often lean or tilt to the side of the lesion.


5. Autonomic nervous system nuclei and tracts. Descending sympathetic system axons traverse the lateral medulla in the lateral reticular formation; dysfunction causes an ipsilateral Horner syndrome. The dorsal motor nucleus of the vagus is sometimes affected, leading to tachycardia and a labile increased blood pressure.


6. Nucleus ambiguus. When the infarct extends medially, it often affects this nucleus, causing hoarseness and dysphagia. The pharynx and palate are weak on the side of the lesion, sometimes causing patients to retain food within the piriform recess of the pharynx. A crowlike cough represents an attempt to extricate food from this area.


7. At times, there is also ipsilateral facial weakness, perhaps related to ischemia of the caudal part of the seventh nerve nucleus, just rostral to the nucleus ambiguus, or involvement of corticobulbar fibers going toward the seventh nerve nucleus.


8. Abnormal respiratory control may also be found, especially in bilateral lateral medullary lesions. Hypoventilation is probably related to involvement of the nucleus of the solitary tract, nucleus ambiguus, nucleus retroambiguus, and nuclei parvocellularis and gigantocellularis.


Only gold members can continue reading. Log In or Register to continue

Stay updated, free articles. Join our Telegram channel

Sep 2, 2016 | Posted by in NEUROLOGY | Comments Off on Arteries of Posterior Cranial Fossa

Full access? Get Clinical Tree

Get Clinical Tree app for offline access