Tailored temporal lobectomy for mesial temporal lobe epilepsy: Can we minimize visual field defect? Result of a prospective study

behalf of the Epilepsy Surgery Group

Background: Traditional anterior temporal lobectomy for mesial temporal epilepsy is associated with high chance of visual field (VF) defect ranged from 50% to 100%.[1] [2] [3] [4] [5] [6] A review in 2008 of our own series showed 68% upper quadrant VF defect contralateral to the side of operation (unpublished). Our further study on the distance between the anterior tip of Myer's lobe and the temporal lobe pole using Diffusion Tensor Tractography (DTT) among the Southern Chinese population showed significant individual variations ranged from 15 to 17 mm.[7] We hypothesized that tailored anterior temporal lobectomy could minimize the VF defect. We have carried out a prospective study comparing with the historical series.

Materials and methods: A prospective study for all epilepsy surgery cases requiring resection of mesial temporal structure from 2009 till 2015. The Myer's loop was delineated using DTT. Navigation was used to guide the anterior temporal lobectomy. All cases had pre-operative and post-operative VF perimetry done.

Results: The prospective cohort (study group) composed of 25 cases. 3 cases were excluded from VF analysis because pre-existing VF defect. Among the 23 cases, new VF defect was found in 8 cases (32%). Comparing with the historical group, the reduction of VF defect was very close to significance (P = 0.052). Seizure outcome of Engel classification I were 73% and 69% for the study and historical group respectively.

Conclusion: Using DTT to delineate the Myer's loop and to operate under navigation guidance, tailored temporal lobectomy for mesial temporal resection may reduce the chance of VF defect significantly post-operatively without compromise seizure free outcome.

• References

• 1 Marino P, Rasmussen T. Visual field changes after temporal lobectomy in man. Neurology 1968; 18: 825-835
• 2 Katz A, Awad I, Kong AK. et al. Extent of resection in temporal lobectomy for epilepsy. II. Memory changes and neurologic complications. Epilepsia 1989; 30: 763-771
• 3 Tecoma E, Laxer K, Barbaro N. et al. Frequency and characteristics of visual field deficits after surgery for mesial temporal sclerosis. Neurology 1993; 43: 1235-1238
• 4 Bjork A, Kugelberg E. Visual field defects after temporal lobectomy. Acta Ophthalmol 1957; 35: 210-216
• 5 Falconer M, Wilson J. Visual field changes following anterior temporal lobectomy: their significance in relation to Meyer's loop. Brain 1958; 81: 1-14
• 6 Hughes T, Abou-Khalil B, Lavin P. et al. Visual field defects after temporal lobe resection. A prospective quantitative analysis. Neurology 1999; 53: 167-172
• 7 Wang YX, Zhu XL, Siu D. et al. The use of diffusion tensor tractography to measure the distance between the anterior tip of the Meyer loop and the temporal pole in a cohort from Southern China. J Neurosurg 2010; 113: 1144-1151