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. 2000 Aug;84(8):884–889. doi: 10.1136/bjo.84.8.884

Anatomy of optic nerve radiations as assessed by static perimetry and MRI after tailored temporal lobectomy

P Krolak-Salmon 1, M Guenot 1, C Tiliket 1, J Isnard 1, M Sindou 1, F Mauguiere 1, A Vighetto 1
PMCID: PMC1723582  PMID: 10906097

Abstract

AIMS—To determine the course of optic nerve radiations in the temporal lobe, especially their retinotopic organisation and the anterior limit of the Meyer's loop.
METHODS—18 adult patients who had undergone a tailored temporal lobectomy for epilepsy were included in this study between 1994 and 1998. The rostrocaudal extent of the lateral temporal lobe resection assessed intraoperatively by the surgeon and by postoperative MRI was compared with the postoperative visual fields determined by automated static perimetry (ASP).
RESULTS—15 patients (83%) presented a postoperative visual field deficit (VFD) confined to the superior homonymous field contralateral to the side of the resection. All degrees from a minimal upper field loss to a complete quadrantanopia were observed. The VFDs were somewhat stereotyped, predominating along the vertical meridian. The smallest anteroposterior resection resulting in a VFD was limited to 20 mm from the tip of the temporal lobe. A relation was observed between the extent of the lateral resection in front of the second and third convolutions and the occurrence and extent of postoperative VFDs. No patient reported persisting subjective visual impairment.
CONCLUSION—The high frequency of postoperative VFDs appears to be due to the greater sensitivity of ASP. The characteristics of the stereotyped VFDs allow new conclusions about the course and retinotopy of optic nerve radiations. The anterior limit of Meyer's loop is likely to be located more rostrally than previously believed.



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Figure 1  .

Figure 1  

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Examples of postoperative horizontal T1 weighted MRI of each group depending on the rostrocaudal extent of the temporal resection. (A) Group 1 (resection of less than one third). (B) Group 2 (resection between one third and two thirds). (C) Group 3 (resection over two thirds). The levels of the MRI slices are different in order to show the best view of the posterior limit of the temporal resection.

Figure 2  .

Figure 2  

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Examples of each type of quadrantanopia defined by the extent of the visual field defect. (A) Left mild quadrantanopia. (B) Left moderate quadrantanopia. (C) Right total quadrantanopia.

Figure 3  .

Figure 3  

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Distribution of the different types of quadrantanopias in the three groups depending on the anteroposterior extent of the lateral temporal resection in front of second and third convolutions. Columns represent the percentage of patients in each group (ordinate) with, respectively, no visual field deficit, mild, a moderate, or a total quadrantanopia (abscissa).

Figure 4  .

Figure 4  

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The geniculocalcarine radiation as proposed by Harvey Cushing (dotted lines),22 completed by our suggestion of a more rostral anterior limit of optic nerve radiations (OR) in the temporal lobe.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

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