The role of transcranial Doppler in nonarteritic ischemic optic neuropathy

To investigate through the use of cerebral Doppler technology whether emboli are a more common cause of nonarteritic anterior ischemic optic neuropathy (NAION) than previously recognized.

Eleven patients with a recent (<121 days) history of nonarteritic anterior ischemic optic neuropathy and 10 age-matched controls (event > 121 days) were examined using a Nicolet Pioneer 2020 transcranial Doppler (TCD) unit with a 2-MHz bilateral continuous monitoring capability. The right and left middle cerebral arteries were evaluated simultaneously for 30 minutes at a depth of 50 to 55 mm, and the number of emboli, blood flow velocities, and pulsatility indices were recorded. Data were stored by computer, and hard-copy color recordings were made.

None of 11 patients with a recent history of NAION demonstrated microemboli by TCD examination. One patient in the control group who had a remote history of NAION had a microembolic event rate of 12 per hour (six over 30 minutes). This patient had a history of prosthetic cardiac valve replacement and was taking anticoagulation medication at the time of the examination.

Our study did not reveal an increased incidence of embolic events in patients with NAION when they were examined in a transcranial Doppler study of the middle cerebral arteries. This study does not support embolism as a frequent cause of NAION.