A 22-year-old Caucasian female is brought to your office by her boyfriend after he found her unconscious on the bed. He says that he is unaware of her past medical history, but remembers one similar episode that resolved completely. Her temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, pulse is 90/min, and respirations are 18/min. The patient is unresponsive to verbal and tactile stimuli. Physical examination reveals a symmetric decrease in muscular tone and normal deep tendon reflexes. Pupils are symmetric, 5mm, and reactive to light. Irrigation of the right external auditory canal with cold water reveals a transient, conjugate, slow deviation of gaze to the right, followed by saccadic correction to the midline. Which of the following is the most likely cause of this patient's condition?

Question

A 22-year-old Caucasian female is brought to your office by her boyfriend after he found her unconscious on the bed.  He says that he is unaware of her past medical history, but remembers one similar episode that resolved completely.  Her temperature is 36.7 C (98 F), blood pressure is 130/80 mm Hg, pulse is 90/min, and respirations are 18/min.  The patient is unresponsive to verbal and tactile stimuli.  Physical examination reveals a symmetric decrease in muscular tone and normal deep tendon reflexes.  Pupils are symmetric, 5mm, and reactive to light.  Irrigation of the right external auditory canal with cold water reveals a transient, conjugate, slow deviation of gaze to the right, followed by saccadic correction to the midline.  Which of the following is the most likely cause of this patient's condition?

Quizplus · Accepted Answer

Explanation: The clinical scenario described above illustrates the importance of oculovestibular testing in the differential diagnosis of coma. Caloric stimulation of the vestibular apparatus is performed by irrigation of the external auditory canal with cold water. A normal response is characterized by a transient, conjugate, slow deviation of gaze to the side of the stimulus (brainstem-mediated), followed by saccadic correction to the midline (cortical correction). A caloric response cannot be voluntarily suppressed; therefore, the normal oculovestibular reaction strongly suggests psychogenic coma. (Choices A and D)Metabolic or supratentorial/infratentorial causes of coma usually disrupt brainstem-mediated or cortical components of the caloric response. (Choices B and C)Botulism and Guillain-Barre syndrome lead to the paralysis of skeletal muscles, but rarely result in a true coma. Educational Objective: A normal reaction to caloric stimulation of the external auditory canal strongly suggests psychogenic coma.

A 22-Year-Old Caucasian Female Is Brought to Your Office by Her