Lateral medullary syndrome results from occlusion of the PICA (Figure IV-5-15).
The cranial nerves or nuclei involved in the lesion are the vestibular or the cochlear parts of CN VIII, the glossopharyngeal and the vagus nerves, and die spinal nucleus or tract of V. The long tracts involved are the spinothalamic tract and the descending hypothalamic fibers.
Spinothalamic tract lesions produce a pain and temperature sensation deficit in the contralateral limbs and body.
Lesions of descending hypothalamic fibers produce an ipsOateral Horner syndrome (i.e., miosis, ptosis, and anhidrosis).
Lesions of the vestibular nuclei and pathways may produce nystagmus, vertigo, nausea, and vomiting. If there is a vestibular nystagmus, the fast component will be away from the side of the lesion.
Lesions of the cochlear nucleus or auditory nerve produce an ipsiiateral sensorineural hearing loss.
Lesions of the vagus nerves exiting the medulla may produce dysphagia (difficulty in swallowing) or hoarseness. The palate will droop on the affected side, and the uvula will deviate away from the side of the lesion.
Lesions of the glossopharyngeal nerve result in a diminished or absent gag reflex.
Lesions of the spinal tract and nucleus of the trigeminal nerve produce a loss of just pain and temperature sensations on the ipsiiateral side of half the face. Touch sensations from the face and the corneal blink reflex will be intact. In lateral medullary syndrome, the pain and temperature losses are alternating; these sensations are lost from the face and scalp ipsilateral to the lesion but are lost from the contralateral limbs and trunk.
Taste sensations may be altered if the solitary nucleus is involved.
Nucleus XII Vestibular nucleus VIII Nucleus solitarius - VII & IX Spinal tract V Nucleus V
Nucleus ambiguus - IX & X Spinothalamic tract
Figure IV-5-15. Lateral Medullary Syndrome (Wallenburg Syndrome)
Inferior cerebellar peduncle(ICP) Spinal V
Spinothalamic tract Vestibular nudei Descending hypothalamics Nucleus ambiguus (fibers of IX, X)
Ipsilateral limb ataxia Ipsilateral pain and temperature loss —face Contralateral pain and temperature loss—body Vomiting, vertigo, nystagmus—away from lesion side Horner's syndrome (always ipsilateral)
Ipsilateral paralysis of the vocal cord, dysphagia, palatedroop
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