CLINICAL CASE | Dissociated Somatic Sensory Loss, Ataxia, and Unilateral Pupillary Constriction, Eyelid Droop and Facial Redness
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 were markedly decreased on the left side of his face, including the left side of his oral cavity. Tactile sensation was preserved bilaterally on his face. Pain and temperature sensations were diminished on the right side of the scalp, neck, limbs, and trunk. Touch and limb proprioception were normal bilaterally. There was a loss of the gag reflex on the left.
His movements were ataxic on the left side, on finger-nose-finger and heel-to-shin testing. He had difficulty making rapidly alternating movements (dysdiadochokinesia) with the left arm. Corresponding right limb functions were normal. He had difficulty standing, and the limited walking he is able to accomplish was associated with a broad-based gait. He was not weak at the hip, knee, and ankle. His voice sounded hoarse. He was able to extend his tongue along the midline. On further examination, the patient also was noted to have mild ptosis on the left. His pupils were reactive to light, but his left pupil was constricted, compared with the right. Finally, the left side of his face was reddish in color, and felt 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. Through what region of the brain stem do descending hypothalamic fibers descend?
3. What is a major function of the descending hypothalamic projection?
4. What ascending pathways transmit pain, temperature sense, and tactile information from the limbs and trunk?
5. What cranial nerves transmit facial pain information and laryngeal muscle control?
6. Is ataxia a sign of an acute lesion of the pyramidal system, cerebellum, or basal ganglia? 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 ...