Vertebral-Basilar Case 4: Unresponsive
The patient showed no spontaneous movement of her face, tongue, neck, trunk or limbs. She was intubated to protect her airway. She was considered to be totally unresponsive until a medical student discovered that she could move her eyes vertically on command. Using a code of up for "yes" and down for "no," the student demonstrated that the patient knew what hospital she was in, how long she had been there, her diagnosis, the names of her doctors and nurses and many day-to-day events of her hospital stay. Although she had no other voluntary movements except vertical eye movements and the ability to lift her eyelids, her somatic sensation, vision, hearing and chemical senses were all preserved.
Diagrams
Dx
Occlusion of Basilar Artery in Rostral Pons
Note
Expert Note Case 4.
Unresponsive
In this patient, occlusion of the basilar artery just distal to the superior cerebellar arteries had produced infarction of the base of the rostral pons bilaterally. Interruption of the corticobulbar and corticospinal tracts caused the complete paralysis of all voluntary movements except certain eye movements. This neurologic condition is termed the locked-in state.
Voluntary horizontal eye movements were impossible because they require intact projections from the frontal lobe (via superior colliculus) to structures in the caudal pons. Vertical eye movements were spared since the entire pathway for voluntary vertical eye movements is contained in the midbrain (the location of brainstem vertical gaze centers and the 3rd and 4th nuclei and nerves) and forebrain, both of which were spared because they are located rostral to the lesion.
The reticular formation and other structures located in the midbrain continued to get adequate blood flow, accounting for the patient's alertness, awareness of herself and her surroundings and ability to perceive sensory stimuli. It is likely that the size and arrangement of vessels in her circle of Willis allowed enough blood to flow from the internal carotid arteries through the posterior communicating and into the posterior cerebral arteries to supply these areas.