Anatomic Study on Neuroendoportal Transcortical Approach to Lateral Ventricles

Microsurgical endoportal MRI/US-navigated approach for the resection of large intraventricular tumours: a 20-consecutive patients case series

OBJECTIVES

Deep lesions located in lateral and third ventricles can be accessed thorough interhemispheric transcallosal or transcortical trans-ventricular approaches. Traditional brain retractors are made by 'non-cerebral engineered' spatulas, which do not equally distribute pressure on surrounding structures damaging brain. In this paper, we present a series of 20 intraventricular tumours resected through a MRI/US-navigated microscopic transcortical endoportal approach.

PATIENTS AND METHODS

Between January 2014 and December 2017, 20 patients underwent US-MRI neuronavigated (Esaote^®, Genova, Italy) transcortical endoportal (Vycor^® Viewsite Brain Access System TC Model, Vycor^® Medical Inc., Boca Raton, FL) surgery for intraventricular deep-seated lesions with the intent to reach maximal safe resection.

RESULTS

Gross total removal was achieved in 14 patients (70%). The only prognostic factor that resulted in statistical significance related to surgical radicality from multivariate analysis was white matter infiltration (p = 0.043), regardless of other tumour (dimensions, origin and location inside ventricular system, histopathology) and patient (age, gender, clinical presentation) characteristics. The mean duration of surgery was 225.9 min (± 59). Neither critical events, nor major bleedings, nor intraoperative deaths occurred during surgery. One case of postoperative CSF infection (5%) was registered. Six patients (30%) required permanent CSF drainage system (Ommaya reservoir, VP shunt) in the postoperative period. The mean Functional Independence Measure (FIM) score at last follow-up was 105 (range: 65-124).

CONCLUSIONS

Transcortical transventricular endoportal surgery seems to be a valuable alternative to transcallosal surgery, although further prospective multicentre studies with larger number of patients, evaluation of pre- and post-operative neuropsychological outcomes and achievement of postoperative DTI and f-MRI are needed to confirm our results.

Impact of C-shaped skin incision on surgical operability in the retrosigmoid approach: when a good start is half of the job

BACKGROUND

The retrosigmoid approach (RSA) is one of the routes of choice to approach tumors and vascular lesions of the cerebellopontine angle. Among different types of skin incisions and soft tissue dissection techniques, the most widely used variants comprise the straight/lazy S-shaped and the C-shaped incisions. Several reports discuss advantages in terms of functional and clinical outcomes of the C-shaped incision, but scientific considerations about the critical impact of this kind of incision on surgical operability are still extremely limited.

OBJECT

Authors comparatively analyze the advantage provided by C-shaped incision in RSA in terms of anatomic exposure and surgical operability, compared with straight/lazy S-shaped one.

METHODS

A comparative microanatomical laboratory investigation was conducted. The operability score (OS) was applied for quantitative analysis of surgical operability.

RESULTS

C-shaped incision, providing a significant reduction of the overall working distance (-13%) together with an overall increase of the maneuverability area (+ 204.9%), did improve the conizing effect on the surgical corridor. It optimized overall maneuverability of surgical instruments, in terms of angle of attack (+ 27.7%), as well as maneuverability arc (+ 122%), on the entire surgical field. C-shaped incision ensured good operability on all surgical targets (OS ranging from 2 to 3), most significantly improving surgical maneuverability at the porus trigeminus and internal acoustic meatus.

CONCLUSION

C-shaped incision in the RSA significantly improves anatomic exposure and surgical operability as compared with straight/lazy S-shaped incision.

Endoscope-Assisted Neuroportal Transcerebellar Approach to the Fourth Ventricle: An Anatomical Study

BACKGROUND AND STUDY AIMS

 Minimally invasive approaches to deep-seated lesions still represent a fundamental issue in modern neurosurgery. Tubular retractors allow to enhance the operability of intraventricular lesions, minimizing the risk of damages to brain parenchyma. Increasing interest for portal devices has been mainly focused on supratentorial pathologies, while transportal approaches in the posterior cranial fossa have been rarely described. In the present study, the authors aimed to investigate the surgical exposure and operability obtained with a microsurgical neuroportal transcerebellar approach targeting the fourth ventricle, assisted by endoscopic exploration.

MATERIAL AND METHODS

 Six cadaveric specimens were provided for anatomical microsurgical dissection and Vycor ViewSite Brain Access System was used as tubular retractor. Surgical feasibility of the neuroportal transcerebellar approach was demonstrated through a definable and measurable parameter, the operability score.

RESULTS

 The neuroport provided a surgical corridor away from eloquent structures to target the whole fourth ventricle cavity, preventing injury to cerebellar nuclei and white matter pathways and, potentially, minimizing the risk of surgical morbidity. Maximal operability was reached in the pontomedullary junction and medullary area of the ventricular floor. Transportal endoscopic assistance contributed to a further extension of surgical exposure in blind spots, corresponding to the ipsilateral lateral recess, the uppermost part of the fourth ventricle, and the obex.

CONCLUSION

 The neuroportal transcerebellar approach represents a viable alternative route to the fourth ventricle, avoiding vermian splitting or subarachnoid dissection of the cerebellomedullary cistern. Endoscopic assistance enhances the exposure of the surgical field and accomplishes a valid instrument for intraventricular orientation to ease microsurgical procedures.