Vertebral-Basilar Case 3: Brisk Reflexes
The patient had a pure motor hemiplegia involving the arm and leg of one side of the body. Reflexes in the paralyzed arm and leg were brisk and the Babinski sign was dorsiflexor. There were no accompanying abnormal sensory or visual findings, or cognitive deficits such as aphasia or neglect.
Diagrams
Note
Expert Note Case 3.
Brisk Reflexes
The patient had suffered a lacunar stroke in the base of the pons caused by occlusion of a small medial penetrating branch of the basilar artery. The damage interrupted the corticospinal tract (located in the base of the pons) which produced contralateral upper motor neuron paralysis of the arm and leg. The same clinical findings may be seen after a lacunar stroke in the internal capsule due to occlusion of a lenticulostriate artery. However, in pontine lesions, the face is usually spared because the corticobulbar fibers have separated from the corticospinal tract at this level and are located much farther dorsal. By contrast, the corticobulbar and corticospinal tracts run close to each other in the posterior limb of the internal capsule and therefore can be damaged together, producing contralateral paralysis that involves the lower face as well.
If the pontine lesion had been less severe, producing a milder motor problem (e.g., hemiparesis instead of hemiplegia), then there may have been ataxia of the weakened limbs. Ataxia cannot be seen if there is complete limb paralysis--to detect the presence of ataxia (incoordination of voluntary limb movements), the patient must be able to move the limb! Ataxia, indicative of a problem with cerebellar function, presumably reflects damage to the pontine nuclei (griseum pontis) that project their axons to the cerebellum via the middle cerebellar peduncle.