Microvascular decompression of the optic chiasm. Case report.

Elongation of the anterior cerebral artery (ACA) and subsequent compression of the chiasm rarely have been reported as causes of a visual field deficit. Neither has microvascular decompression of the chiasm been described in this circumstance. The authors report on a case of progressive visual deficits caused by compression of the optic apparatus by a right elongated ACA as documented on MR imaging. Microvascular decompression was proposed as treatment. The right A(1) segment was larger than usual and tortuous, transmitting its pulsations into the chiasm. A piece of Teflon was inserted between the A(1) segment and the chiasm. Following surgery, the visual field deficit progressively improved. At 4 months after surgery, the patient's visual fields were normal. Therefore, an elongated ACA can compress the chiasm and result in a visual field deficit. In such circumstances when facing a progressive visual field deficit, microvascular decompression may improve vision.