Intersubject variability in the anterior extent of the optic radiation assessed by tractography

INTRODUCTION Temporal lobe resection for epilepsy involves a risk of damaging the anterior part of the optic radiation, Meyer's loop, causing a contralateral upper quadrant visual field defect. This study aims to assess the intersubject variability in the course of Meyer's loop in vivo by diffusion tensor imaging and tractography. METHODS Seven healthy volunteers and two patients with previous temporal lobe resection were recruited. Diffusion tensor imaging and tractography were used to visualize the optic radiation. The distances from the anterior edge of Meyer's loop to landmarks in the temporal lobe were calculated. RESULTS In the healthy subjects, the mean distance between the most anterior part of Meyer's loop and the temporal pole was 44 mm (range 34-51 mm). Meyer's loop did not reach the tip of the temporal horn in any subject. A disruption in Meyer's loop could be demonstrated in the patient with quadrantanopia after temporal lobe resection. CONCLUSIONS Meyer's loop has a considerable variability in its anterior extent. Tractography may be a useful method to visualize Meyer's loop, and assess the risk of a visual field defect, prior to temporal lobe resection.

[1]  Toshiaki Taoka,et al.  Diffusion tensor imaging in cases with visual field defect after anterior temporal lobectomy. , 2005, AJNR. American journal of neuroradiology.

[2]  J. Isnard,et al.  MRI Assessment of the Anatomy of Optic Radiations after Temporal Lobe Epilepsy Surgery , 2000, Stereotactic and Functional Neurosurgery.

[3]  H. Lüders,et al.  Extent of Resection in Temporal Lobectomy for Epilepsy. II. Memory Changes and Neurologic Complications , 1989, Epilepsia.

[4]  M. Kraut,et al.  Diffusion tensor MR imaging of the brain and white matter tractography. , 2002, AJR. American journal of roentgenology.

[5]  Ugur Türe,et al.  Impact of temporal lobe surgery. , 2004, Journal of neurosurgery.

[6]  J. Voogd,et al.  The human central nervous system , 1978 .

[7]  G. Pearlson,et al.  Diffusion Tensor Imaging and Axonal Tracking in the Human Brainstem , 2001, NeuroImage.

[8]  A. Schleicher,et al.  Mapping of Histologically Identified Long Fiber Tracts in Human Cerebral Hemispheres to the MRI Volume of a Reference Brain: Position and Spatial Variability of the Optic Radiation , 1999, NeuroImage.

[9]  J. S. Duncan,et al.  MR tractography predicts visual field defects following temporal lobe resection , 2005, Neurology.

[10]  K. Malmgren,et al.  Visual field defects after temporal lobectomy – comparing methods and analysing resection size , 2004, Acta neurologica Scandinavica.

[11]  E. Ludwig,et al.  Atlas cerebri humani , 1956 .

[12]  B. Abou-Khalil,et al.  Visual field defects after temporal lobe resection , 1999, Neurology.

[13]  Jan Goffin,et al.  Anatomy of the Anterior Temporal Lobe and the Frontotemporal Region Demonstrated by Fiber Dissection , 2004, Neurosurgery.

[14]  Susumu Mori,et al.  Fiber tracking: principles and strategies – a technical review , 2002, NMR in biomedicine.

[15]  T. Rasmussen,et al.  Visual field changes after temporal lobectomy in man , 1968, Neurology.

[16]  C. Wilson,et al.  Asymmetry and ventral course of the human geniculostriate pathway as determined by hippocampal visual evoked potentials and subsequent visual field defects after temporal lobectomy , 2004, Experimental Brain Research.

[17]  Derek K. Jones,et al.  Occipito-temporal connections in the human brain. , 2003, Brain : a journal of neurology.

[18]  I. Jensen,et al.  TEMPORAL LOBE EPILEPSY AND NEURO‐OPHTHALMOLOGY , 1976, Acta ophthalmologica.

[19]  H. Moser,et al.  Imaging cortical association tracts in the human brain using diffusion‐tensor‐based axonal tracking , 2002, Magnetic resonance in medicine.

[20]  P. Basser.  Inferring microstructural features and the physiological state of tissues from diffusion‐weighted images , 1995, NMR in biomedicine.

[21]  Tsunehiko Nishimura,et al.  Tractography to depict three layers of visual field trajectories to the calcarine gyri. , 2005, American journal of ophthalmology.

[22]  U. Ebeling,et al.  Neurosurgical topography of the optic radiation in the temporal lobe , 2005, Acta Neurochirurgica.

[23]  W. T. Shults,et al.  Visual field deficits in conventional anterior temporal lobectomy versus amygdalohippocampectomy , 2000, Neurology.

[24]  B. Rydenhag,et al.  Complications of Epilepsy Surgery after 654 Procedures in Sweden, September 1990–1995: A Multicenter Study Based on the Swedish National Epilepsy Surgery Register , 2001, Neurosurgery.

[25]  Akira Yamaura,et al.  MR demonstration of partial lesions of the lateral geniculate body and its functional intra-nuclear topography , 2003, Clinical Neurology and Neurosurgery.

[26]  W T Blume,et al.  A randomized, controlled trial of surgery for temporal-lobe epilepsy. , 2001, The New England journal of medicine.

[27]  Kensuke Kawai,et al.  Functional Monitoring for Visual Pathway Using Real-time Visual Evoked Potentials and Optic-radiation Tractography , 2005, Neurosurgery.

[28]  J. L. Wilson,et al.  Visual field changes following anterior temporal lobectomy: their significance in relation to Meyer's loop of the optic radiation. , 1958, Brain : a journal of neurology.

[29]  F. Drislane,et al.  The field defects of anterior temporal lobectomy: a quantitative reassessment of Meyer's loop. , 2005, Brain : a journal of neurology.