Fangxiang Chen and Peter Nakaji
An optimal entry point for endoscopic third ventriculostomy (ETV) helps protect critical structures from undue manipulation. A commonly accepted ideal entry point is 3 cm from the midline and 1 cm anterior to the coronal suture. The authors of this study reexamine this ideal entry point.
Trajectory views from MR images or CT scans used for cranial image guidance in 53 patients (age range 3–85 years) who had undergone ETV were retrospectively evaluated. The trajectory from the tuber cinereum back through the center of the foramen of Monro was projected to the surface of the head. The relation of the entry point to the midline and the coronal suture was established.
The mean perpendicular distance from the ideal entry point to the midline was 30.1 ± 7 mm (median 31.9 mm, range 12.5–42.2 mm). The mean perpendicular distance to the coronal suture was 8.9 ± 14.1 mm posterior (median 10.4 mm), ranging from 30.6 mm anterior to 35.8 mm posterior. The entry point tended to be located more posteriorly in women and adults: 5.8 ± 15.4 mm posterior in males versus 13.1 ± 13.2 mm posterior in females (p = 0.08) and 9.1 ± 14.8 mm posterior in adults versus 8.2 ± 11.7 mm posterior in children (p = 0.84).
While the entry point may need to be modified from the ideal trajectory for other anatomical reasons, such as a trajectory through the motor cortex, in general, the authors found that the optimal entry point for ETV was more posterior than previously published and highly variable. Using image guidance or a customized trajectory based on analysis of a patient's own imaging is highly preferable to using an empirical ideal trajectory.
Fangxiang Chen, Tsinsue Chen, and Peter Nakaji
The coronal suture is often used as an empirical landmark for the entry point for endoscopic third ventriculostomy. The trajectory for the approach is often drawn based on midsagittal MRI findings. However, because the coronal suture is not perpendicular to the midline, this method may be inaccurate.
The junction of the coronal and sagittal sutures was exposed at the outer table of the cranium of 15 cadavers. An ideal coronal line was established perpendicular to the sagittal suture at the junction of the sagittal and coronal sutures. The distance from this ideal coronal line at the level of the coronal-sagittal junction to the actual coronal suture was measured at 1-cm intervals. The measured distance between the 2 planes was termed the distance to the coronal suture.
The coronal suture bows forward as it moves from medial to lateral. From 1–6 cm lateral to the sagittal suture, the distance to the coronal suture was 0.1, 0.3, 0.5, 0.8, 1.0, and 1.4 cm, respectively. There was no significant difference between the right and left sides.
The position of a bur hole for endoscopic third ventriculostomy should be moved posteriorly with respect to the coronal suture the more laterally it is placed. Although the adjustment is small, it may be crucial. Failure to make this adjustment may result in suboptimal bur hole placement and increase the risk of morbidity.
Robert F. Spetzler, Felipe C. Albuquerque, Joseph M. Zabramski, and Peter Nakaji
M. Yashar S. Kalani, Nikolay L. Martirosyan, Peter Nakaji, and Robert F. Spetzler
The supracerebellar infratentorial approach provides access to the dorsal midbrain, pineal region, and tentorial incisura. This approach can be used with the patient in a sitting, prone, park-bench, or supine position. For a patient with a supple neck and favorable anatomy, we prefer the supine position. The ipsilateral shoulder is elevated, the head turned to the contralateral side, the chin is tucked, and the neck extended toward the floor to open the craniocervical angle for added working room. Care must be taken to place the craniotomy laterally to make use of the ascending angle of the tentorium for ease of access to deep-seated lesions.
The video can be found here: https://youtu.be/BZh6ljmE23k.
Paul Larson, Peter Nakaji, Walter Stummer, and John Pollina
Nikolay L. Martirosyan, M. Yashar S. Kalani, Peter Nakaji, and Robert F. Spetzler
The anterior interhemispheric approach is a workhorse for treatment of lesions in the third ventricle. In this case, we demonstrate the utility of this approach for resecting a complex third ventricular cavernous malformation. We discuss patient positioning, optimal location of the craniotomy, and surgical resection techniques for safe removal of these lesions. We also demonstrate the importance of gravity retraction using the falx to prevent injury to the dominant frontal lobe.
The video can be found here: https://youtu.be/38woc28er7M.
Harjot Thind, Douglas A. Hardesty, Joseph M. Zabramski, Robert F. Spetzler, and Peter Nakaji
The successful treatment of an intracranial dural arteriovenous fistula (dAVF) requires complete obliteration of blood flow through the fistulous point. Surgical ligation is often used along with endovascular techniques. Digital subtraction angiography (DSA) can be used to confirm fistula obliteration; however, this technique can be cumbersome intraoperatively and difficult to correlate anatomically with the surgical field. Near-infrared indocyanine green (ICG) videoangiography has been described as a complementary tool for this purpose.
The authors examined intracranial dAVF cases in which microscope-integrated intraoperative ICG videoangiography was used to identify and/or confirm obliteration of the dAVF during surgery. Retrospective evaluation of all intracranial dAVF cases treated with surgical ligation over a 10-year period at the Barrow Neurological Institute (n = 47) revealed 28 cases in which ICG videoangiography was used. The results were compared with findings on preoperative and intraoperative or postoperative DSA.
ICG videoangiography successfully confirmed the fistulous point intraoperatively in 96% (22/23) of the cases. It also revealed complete obliteration of fistulas, comparable to intraoperative or postoperative DSA, in 91% (21/23) of the cases. The false-negative rate of ICG was 8.7% (2/23), which is similar to the false-negative rate of intraoperative DSA alone (10.5% [2/19]).
Microscope-based ICG videoangiography provides real-time information about the intraoperative anatomy of dAVFs. In addition, it can confirm complete obliteration of a fistula. This technique may be useful during dAVF surgery as an independent form of angiography or as an adjunct to intraoperative or postoperative DSA.
Scott D. Wait, Adib A. Abla, Brendan D. Killory, Peter Nakaji, and Harold L. Rekate
Hypothalamic hamartomas (HHs) are devastating lesions causing refractory epilepsy, rage attacks, social ineptitude, and precocious puberty. Microsurgical and/or endoscopic resection offers an excellent risk/benefit profile for cure or improvement of epilepsy.
The authors reviewed a prospective database maintained during the first 7 years of the Barrow Hypothalamic Hamartoma program. They describe and illustrate their surgical methods, and they review data from several previous publications regarding surgical outcome.
To date, the authors have performed surgery in 165 patients for symptomatic HHs. Patients underwent an endoscopic, transcallosal, or skull base approach, or multiple approaches. Twenty-six patients (15.8%) required more than 1 treatment for their HH.
Microsurgical and endoscopic resection of symptomatic HHs are technically demanding but can be performed safely with excellent results and an acceptable risk profile. Meticulous attention to the subtleties of surgical management helps optimize outcomes.