The patient in this case was diagnosed with a lateral medullary stroke on the right with Wallenberg syndrome.
Neurons relaying pain and temperature sensation from the right side of the face synapse in the descending spinal nucleus of the trigeminal nerve, which lies in the dorsolateral aspect of the brainstem (Figure 2).
Thereafter, the pathway crosses (as the quintothalamic tracts) and ascends to the thalamus. For the limbs and trunk, the neurons of the spinothalamic tract from the left side of the body pass into the spinal cord, where they ascend for 1 or 2 levels (via Lissauer's tract) and then synapse. The second-order neurons then cross to the right side of the spinal cord (via the anterior commissure, just anterior to the central canal of the cord) and then ascend in the anterolateral aspect of the spinal cord up into the right side of the brainstem. In the brainstem, the spinothalamic tract lies laterally.
This patient had impairment of pain and temperature (ie, spinothalamic) sensation on the right side of the face and the left side of the body. These contralateral findings are characteristic of a right lateral medullary lesion. The patient also had reduced palatal movements and gag reflex on the right side indicative of involvement of the right IX (glossopharyngeal) and X (vagus) cranial nerves. These cranial nerves, as well as the descending sympathetic fibers (patient had a right-sided Horner sign), are also found in the dorsolateral aspect of the right side of the medulla (Figure 3).
The presence of vertigo and right-sided ataxia was due to involvement of the vestibular nucleus and cerebellar pathways (as they pass into the cerebellum through the inferior cerebellar peduncle), respectively, on the right side. The nucleus and the fascicles of the hypoglossal nerve lie medially within the medulla, and the pyramidal pathways lie anteromedially as they pass through the medulla. The joint position and vibration sense modalities pass up the spinal cord on the ipsilateral side and then synapse at the gracile and cuneate nuclei in the lower part of the medulla. The dorsal column pathways then cross (as the internal arcuate fibres) at the level of the lower medulla and pass up the medial aspect of the brainstem as the medial lemnisci. The normal tongue movements and the preserved pyramidal and dorsal column function in this patient indicated that there was sparing of the medial medulla; therefore, this patient had a right-sided lateral medullary syndrome (ie, Wallenberg syndrome), which was determined by brain MRI to be a stroke. The T2-weighted coronal scan showed a high signal abnormality in the right side of the medulla (black arrow, Figure 1).
The presence of prominent right ear pain for 3 days prior to developing neurologic deficits was suggestive of a vertebral artery dissection. In fact, stroke preceded by headache or neck pain should always raise suspicion for cervical arterial dissection. The patient performed vigorous aerobic exercises on an almost daily basis, and these exercises included repetitive high-energy lateral neck flexions. This is likely to have been the cause of an arterial dissection. The diagnosis made was of a dissection of the right vertebral artery and a subsequent infarction of the dorsolateral aspect of the right medulla.
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