CLINICAL CASE | Lateral Medullary Syndrome and Horner Syndrome
A 69-year-old hypertensive man suddenly developed vertigo and left facial numbness. He is unable to stand unassisted.
His sensory and motor functions were tested at the emergency room. Pain and temperature sensations are markedly decreased on the left side of his face, including the left side of his oral cavity. Tactile sensation is preserved bilaterally on his face. Pain and temperature sensations are diminished on the right side of the scalp, neck, limbs, and trunk. Touch and limb propriosensation were normal bilaterally. There is a loss of the gag reflex on the left.
On finger-nose-finger testing of the left arm and heel-to-shin testing of the left leg, his movements are ataxic. He has difficulty making rapidly alternating movements (dysdiadochokinesia) with the left arm. Corresponding right limb functions are normal. He has difficulty standing, and the limited walking he is able to accomplish is associated with a broad-based gait. His voice sounds hoarse. He is able to extend his tongue along the midline.
On further examination, the patient also is noted to have mild ptosis on the left. His pupils were reactive to light, but his left pupil was smaller than the right. Finally, the left side of his face feels dry and warm to touch.
Figure 15–1A is an MRI of the medulla, and Figure 15–1B, a nearby myelin-stained section. The bright dorsolateral region in part A is the site of an infarction.
Answer the following questions on the basis of your reading of this chapter and prior chapters on sensory and motor functions of the dorsolateral medulla.
1. Occlusion of which artery would infarct the medullary region shown on the MRI?
2. Indicate the particular nucleus or tract that, after damage by infarction, produces: (1) ipsilateral facial pain loss, (2) contralateral loss of limb and trunk pain, (3) ataxia, (4) hoarse voice, and (5) ipsilateral ptosis.
Key neurological signs and corresponding damaged brain structures Distribution of the posterior inferior cerebellar artery The site of lesion corresponds to the distribution of the posterior inferior cerebellar artery. The territory supplied by this artery receives little collateral circulation (see Chapter 3). This means that blood flow from a functioning neighboring artery does not take over, as in many regions of the brain. Remaining areas of the medulla at this level are supplied by small, direct branches from the vertebral artery.
Alternating loss of pain and temperature on the left side of the face and right limbs and trunk with preservation of touch The lesion produced a classical sign. Ipsilateral loss of facial pain and temperature sensation is due to interruption of the spinal trigeminal tract, as well as part of the spinal trigeminal nucleus (caudal nucleus). Contralateral loss of pain and temperature sensation on the neck, limbs, and trunk is due to interruption of the anterolateral system, which decussates in the spinal cord (Figure 15–1C). This pattern was considered ...