Lateral medullary and lateral pontine syndromes

What it is

These are the two lateral brainstem stroke syndromes. The lateral medullary syndrome, also called Wallenberg syndrome, sits in the lateral medulla and follows a stroke in the posterior inferior cerebellar artery, PICA, or in the vertebral artery of the same side. The lateral pontine syndrome sits in the pons and follows a stroke in the anterior inferior cerebellar artery, AICA.

How it presents

Localizing them is done in three steps. First the area, from the cranial nerve signs: the medulla gives cranial nerves 9, 10 and 12, so speech and swallowing problems, dysarthria, dysphagia, and tongue or palate and uvula deviation; the pons gives cranial nerves 6 and 7, so diplopia, loss of eye abduction and facial weakness, weakness and not numbness, since numbness is not localizing. Then the tract, medial or lateral. The lateral tracts are the three S's: spinothalamic for pain and temperature, sympathetic for Horner, and spinocerebellar for ataxia and cerebellar signs. Then the side: all cranial nerve lesions are ipsilateral except palate and uvula deviation, which is contralateral, and all tract lesions are contralateral except the sympathetic and spinocerebellar ones, which are ipsilateral. Wallenberg syndrome therefore gives loss of pain and temperature sensation in the ipsilateral face and the contralateral body, from the spinal trigeminal nucleus and the spinothalamic tract; dysphagia, hoarseness and a decreased gag reflex from the nucleus ambiguus; vertigo with nausea and vomiting from the vestibular nuclei; ataxia and dysmetria from the inferior cerebellar peduncle; and Horner syndrome from the sympathetic fibers. Hiccups are also listed. The palate deviates to the contralateral side. The pages do not agree on one item: the lateral medullary list carries ipsilateral motor impairment, while the localizing approach given on the page before it puts motor, hemiplegia and weakness, with the corticospinal tract and so with the medial syndromes, and holds the lateral syndromes to the three S's. Both are set down here as they stand. The lateral pontine syndrome also gives loss of pain and temperature sensation in the ipsilateral face, vertigo with nausea and vomiting, ataxia and dysmetria, and ipsilateral Horner. What is specific to it is ipsilateral hearing impairment, and the facial nerve, which gives ipsilateral facial paralysis with decreased taste from the anterior 2/3 of the tongue and decreased lacrimation and salivation. Ipsilateral facial numbness with the facial palsy is given for it as well.