A 72-year-old woman is found unconscious at home by her daughter. The daughter last spoke to her mother 1 day previously, at which time her mother seemed fine. The patient has diabetes, hypertension, atrial fibrillation, and chronic back pain. Her medications include metformin, lisinopril, warfarin, and oxycodone. On examination her blood pressure is 167/70, pulse 48 beats/minute, respiratory rate 12 breaths/minute and irregular, and temperature 37.2°C (98.9°F). There are no signs of trauma. Neck issupple. The patient does not respond to verbal stimuli. Pupils are equally reactive to light. The oculocephalic reflex (doll’s eye maneuver) is normal. On applying firm pressure to the orbital rim, the patient flexes her right arm, but does not move her left arm.
Which of the following is the most likely cause of her condition?
A. HypoglycemiaThis woman presents with coma that requires rapid and careful evaluation. The most common causes of coma are central nervous system infections (meningitis and encephalitis), structural central nervous system lesions, which produce compression of the brain-stem, metabolic abnormalities, and drug overdose. The neurologic examination is very helpful in the evaluation of comatose patients, and should focus on specific maneuvers: (1) testing for nuchal rigidity, (2) pupillary response to light, (3) patient response to painful stimulus (typically by applying firm pressure to the sternum or orbital rim), and (4) the oculocephalic reflex (doll’s eye maneuver). Neck stiffness and fever in the comatose patient would suggest meningitis or subarachnoid hemorrhage. Pupillary response to light is preserved in metabolic derangements, drug overdose, and early in space occupying lesions. Preserved pupillary light reflex in the absence of an oculocephalic reflex is seen almost exclusively in drug overdose. In space-occupying lesions with early brainstem compression (the so-called diencephalic stage) the pupillary response to light and the oculocephalic reflex are preserved. As brainstem compression progresses to midbrain and then pons compression, pupillary response to light and the oculocephalic reflex are lost. When unilateral arm flexion with painful stimulation occurs in the comatose patient, this suggests a hemispheric mass with mild brainstem compression. As brainstem compression progresses to involve the midbrain, the comatose patient will respond to painful stimulation with arm flexion and leg extension (decorticate posturing). When brainstem compression progresses further to involve the pons, painful stimulation results in extension of both arms and legs (decerebrate posturing). This comatose patient has preserved pupillary and oculocephalic reflexes, and right arm flexion with painful stimulation. This suggests a left hemispheric space-occupying lesion with early brainstem compression. The widened pulse pressure, bradycardia, and irregular breathing (Cushing reflex) also suggest increased intracranial pressure. In this patient on warfarin, these findings are likely due to an acute subdural hematoma, which may occur spontaneously or with trauma (such as falling). Hypoglycemia is uncommon with metformin. Neither hypoglycemia nor drug overdose would cause unilateral arm flexion with painful stimulation. In the absence of fever and neck stiffness, meningitis is unlikely. A lacunar infarct will cause a pure motor or pure sensory stroke but not global brain dysfunction. Anterior cerebral artery occlusion causes motor and sensory deficits of the contralateral leg and foot but does not impair global brain function.