Quantitative anatomical comparison of the ipsilateral and contralateral interhemispheric transcallosal approaches to the lateral ventricle

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OBJECTIVE

The best approach to deep-seated lateral and third ventricle lesions is a function of lesion characteristics, location, and relationship to the ventricles. The authors sought to examine and compare angles of attack and surgical freedom of anterior ipsilateral and contralateral interhemispheric transcallosal approaches to the frontal horn of the lateral ventricle using human cadaveric head dissections. Illustrative clinical experiences with a contralateral interhemispheric transcallosal approach and an anterior interhemispheric transcallosal transchoroidal approach are also related.

METHODS

Five formalin-fixed human cadaveric heads (10 sides) were examined microsurgically. CT and MRI scans obtained before dissection were uploaded and fused into the navigation system. The authors performed contralateral and ipsilateral transcallosal approaches to the lateral ventricle. Using the navigation system, they measured areas of exposure, surgical freedom, angles of attack, and angle of view to the surgical surface. Two clinical cases are described.

RESULTS

The exposed areas of the ipsilateral (mean [± SD] 313.8 ± 85.0 mm2) and contralateral (344 ± 87.73 mm2) interhemispheric approaches were not significantly different (p = 0.12). Surgical freedom and vertical angles of attack were significantly larger for the contralateral approach to the most midsuperior reachable point (p = 0.02 and p = 0.01, respectively) and to the posterosuperior (p = 0.02 and p = 0.04) and central (p = 0.04 and p = 0.02) regions of the lateral wall of the lateral ventricle. Surgical freedom and vertical angles of attack to central and anterior points on the floor of the lateral ventricle did not differ significantly with approach. The angle to the surface of the caudate head region was less steep for the contralateral (135.6° ± 15.6°) than for the ipsilateral (152.0° ± 13.6°) approach (p = 0.02).

CONCLUSIONS

The anterior contralateral interhemispheric transcallosal approach provided a more expansive exposure to the lower two-thirds of the lateral ventricle and striothalamocapsular region. In normal-sized ventricles, the foramen of Monro and the choroidal fissure were better visualized through the lateral ventricle ipsilateral to the craniotomy than through the contralateral approach.

Article Information

Correspondence Mark C. Preul, c/o Neuroscience Publications, Barrow Neurological Institute, St. Joseph’s Hospital and Medical Center, 350 W Thomas Rd., Phoenix, AZ 85013. email: neuropub@dignityhealth.org.

INCLUDE WHEN CITING Published online August 4, 2017; DOI: 10.3171/2017.1.JNS161338.

Disclosures The authors report no conflict of interest concerning the materials or methods used in this study or the findings specified in this paper.

© AANS, except where prohibited by US copyright law.

Headings

Figures

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    Photograph of cadaveric dissection showing the view into the callosotomy through the contralateral interhemispheric approach. aa. = arteries; v. = vein.

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    Photograph of cadaveric dissection showing the lateral wall of the left lateral ventricle. Part of the corpus callosum and the cingulate gyrus were removed and the body of the fornix was resected to expose the lateral ventricle wall. Projection of the 15-mm-long callosotomy is depicted. Approximate positions of the 7 points that define the area of exposure are as follows: A, the uppermost posterior reachable point; B, the uppermost point on the lateral wall at the middle of the callosotomy; C, the uppermost anterior reachable point; D, the lowermost posterior reachable point on the floor of the lateral ventricle; E, the lowermost point on the floor of the lateral ventricle projected at the center of the callosotomy; F, the lowermost anterior reachable point on the floor of the lateral ventricle; and X, the center of the exposed area.

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    Comparison of surgical freedom to the lateral wall of the lateral ventricle through the ipsilateral and contralateral interhemispheric approaches. Surgical freedom is calculated for the 7 points (A, B, C, D, E, F, and X) on the lateral ventricle wall as defined in Fig. 2.

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    Comparison of the surgical freedom to the wall of the lateral ventricle for contralateral (left panel) and ipsilateral (right panel) interhemispheric transcallosal approaches. A gradient color map representing the surgical freedom (A, B, C, D, E, F, and X, as defined in Fig. 2) is imposed on photographs of the anatomical specimen to show anatomical areas allowing different maneuverability of the instruments through the 2 approaches. Green represents greater surgical freedom, red represents less surgical freedom.

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    Comparison of the angles of attack to the selected points (A, B, C, D, E, F, and X, as defined in Fig. 2) on the lateral wall of the lateral ventricle.

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    Comparison of the angle of approach to the surface. An angle close to 90° provides the best visualization of the surface. DXE = lowermost possible angle of view (closer to the hemisphere in the contralateral approach and to the superior sagittal sinus in the ipsilateral approach); UXE = uppermost possible angle of view (closer to the superior sagittal sinus in the contralateral approach and to the hemisphere in the ipsilateral approach).

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    Illustrative Case 1. This 63-year-old man presented with intermittent confusion and left-sided hemiparesis that had slowly evolved over 2 months. He had a history of diabetic peripheral neuropathy and bilateral lower-extremity weakness, and he was wheelchair-bound at baseline. A–C: Axial FLAIR (A) and sagittal (B) and coronal (C) T1-weighted postcontrast MR images showing a hemorrhagic lesion with a large amount of surrounding vasogenic edema in the right basal ganglia region, causing mass effect and midline shift. An anterior contralateral interhemispheric transcallosal approach was performed to remove the tumor. The arrows in panels B and C indicate the trajectory of the approach. D: Schematic illustration showing the positioning and surgical corridor provided by the contralateral interhemispheric transcallosal approach. Panel D: Copyright Barrow Neurological Institute. Published with permission. E–G: Immediate postoperative MR images (E, axial FLAIR; F, axial postcontrast T1-weighted; G, coronal postcontrast T1-weighted) obtained after gross-total resection showing a small area of residual enhancement for which a single Gamma Knife (Leksell; Elekta AB) radiosurgery treatment was administered 3 weeks later. H–J: MR images obtained at the 4-year follow-up visit showing complete resection and absence of tumor recurrence. The patient’s condition was stable. Axial postcontrast T1-weighted image (H), sagittal T2-weighted MR image showing the callosotomy (I), and coronal postcontrast T1-weighted image (J).

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    Cadaveric dissections showing views to the left foramen of Monro through the ipsilateral (left panel) and contralateral (right panel) interhemispheric approaches over the same callosotomy. Insets show position of the head and location of the craniotomy. In normal-size ventricles, the ipsilateral approach provides a straight view through the foramen of Monro to the third ventricle, whereas the view and approach into the third ventricle from the contralateral lateral ventricle is obstructed by the fornix. For illustrative purposes, the callosotomy has intentionally been enlarged more than it would be in normal surgery. Insets: Copyright Barrow Neurological Institute. Published with permission.

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    Illustrative Case 2. This 80-year-old man presented with new-onset facial droop and right-eye ptosis. A–C: Axial (A), sagittal (B), and coronal (C) T1-weighted contrast-enhanced MR images showing a posterolateral mass located within the left wall of the third ventricle. A contralateral anterior interhemispheric transcallosal transchoroidal approach was performed to remove the tumor in the third ventricle. The arrows in panels B and C show the trajectory of the approach. D and E: Postoperative axial (D) and coronal (E) postcontrast T1-weighted MR images showing total resection of the tumor. F: Schematic illustration showing the positioning and surgical corridor provided by the contralateral interhemispheric transcallosal transchoroidal approach. Panel F: Copyright Barrow Neurological Institute. Published with permission.

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