Table of Contents

Optic radiation

upload.wikimedia.org_wikipedia_commons_d_d0_erp_-_optic_cabling.jpg

The optic radiation (OR) is a white matter bundle with a very complex anatomy. Its anterior component bends sharply around the tip of the temporal horn, forming the Meyers Loop 1).

Definition

The optic radiation (also known as the geniculocalcarine tract, the geniculostriate pathway, and posterior thalamic radiation) are axons from the neurons in the lateral geniculate nucleus to the primary visual cortex.

Blood supply

The optic radiation receives blood through deep branches of the middle cerebral artery and posterior cerebral artery.

They carry visual information through two divisions (called Upper and Lower division) to the visual cortex (also called striate cortex) along the calcarine fissure. There is one such tract on each side of the brain. If a lesion only exists in one optic radiation, the consequence is called quadrantanopia.

The optic radiation can be accurately delineated by tractography and propagated onto postoperative images. The technique is fast enough to propagate accurate preoperative tractography onto intraoperative scans acquired during neurosurgery, with the potential to reduce the risk of visual field deficit (VFD) 2).

Importance

Visual field defects (VFDs) due to optic radiation (OR) injury are a common complication of temporal lobe surgery.

Sparing optic radiations can be of paramount importance during epilepsy surgery of the temporal lobe. The anatomical heterogeneity of the Meyers loop of the optic radiations could be assessed by means of diffusion tensor tractography.

The posterior interhemispheric transprecuneus gyrus approach is one of the surgical routes that has been suggested to reach the atrium of the lateral ventricle. It has the advantage of avoiding the disruption of the optic radiations; however, it has a narrow working area that at times makes the execution of this approach rather challenging.

A modification of the approach that might create a better surgical angle and a wider corridor by accessing the atrium from the contralateral side after transection of the falx, named this new approach the “posterior interhemispheric transfalx transprecuneus approach.” 3).

Dorsal loop of the optic radiation

Dorsal loop of the optic radiation.

1)
Bertani GA, Bertulli L, Scola E, Cristofori AD, Zavanone M, Triulzi F, Rampini PM, Carrabba GG. Optic Radiation Diffusion Tensor Imaging Tractography: an Alternative and Simple Technique for the Accurate Detection of Meyer's Loop. World Neurosurg. 2018 May 29. pii: S1878-8750(18)31084-2. doi: 10.1016/j.wneu.2018.05.131. [Epub ahead of print] PubMed PMID: 29857218.
2)
Winston GP, Daga P, Stretton J, Modat M, Symms MR, McEvoy AW, Ourselin S, Duncan JS. Optic radiation tractography and vision in anterior temporal lobe resection. Ann Neurol. 2012 Mar;71(3):334-41. doi: 10.1002/ana.22619. PubMed PMID: 22451201; PubMed Central PMCID: PMC3698700.
3)
Wang S, Salma A, Ammirati M. Posterior interhemispheric transfalx transprecuneus approach to the atrium of the lateral ventricle: a cadaveric study. J Neurosurg. 2010 Nov;113(5):949-54. doi: 10.3171/2010.1.JNS091169. Epub 2010 Feb 12. PubMed PMID: 20151777.