Physiological Localization of the Facial Colliculus during Direct Surgery on an Intrinsic Brain Stem Lesion

Minimally invasive neurosurgery

BACKGROUND

The philosophy and practice of minimally invasive surgery have fundamentally altered the practice of general and gynaecological surgery, and are currently transforming the practice of neurosurgery. The goal of minimally invasive surgery is to reduce tissue disruption and thus morbidity. This is a review of the development, applications, and benefits of minimally invasive neurosurgery, and its wider surgical implications.

METHODS

A synthesis of the literature is presented.

RESULTS

Interactive computer imaging with frame-based and frameless stereotaxy, ultrasonographic and endoscopic techniques are increasingly being used independently and in combination in order to execute minimally invasive approaches and to navigate a safe path within the cranium or spine. Interaction using an interlinking stereotactic instrument or robot between the surgeon, a graphic interface (such as a computer workstation) and the patient, enables precise planning and execution of surgery with exact correspondence of imaging data and the living pathology. The direct influence of virtual reality, cybernetics, robotics, and telepresence will further revolutionize the practice of neurosurgery and will impact increasingly on other surgical disciplines. Safety and precision are further enhanced by intra-operative physiological monitoring techniques. Interventional neuroradiology and stereotactic radiosurgery add further dimensions to the minimally invasive approach and may not only diminish the need for open surgery, but in selected cases obviate the need altogether.

CONCLUSIONS

Minimally invasive neurosurgery is a major force in contemporary neurosurgery and many of the current neurosurgical applications will have far-reaching effects on the practice of surgery in general.

Continuous intraoperative electromyographic monitoring of cranial nerves during resection of fourth ventricular tumors in children

The authors reviewed the results of continuous intraoperative electromyographic (EMG) monitoring of muscles innervated by cranial nerves in 17 children whose preoperative imaging studies showed compression or infiltration of the fourth ventricular floor by tumor to determine how intraoperative EMG activity correlated with postoperative cranial nerve morbidity. Bilateral lateral rectus (sixth) and facial (seventh) nerve musculature were monitored in all children. Cranial nerve function was documented immediately postoperatively and at 1 year.

Of the 68 nerves monitored, nine new neuropathies occurred in six children (sixth nerve in four children and seventh nerve in five). In five new neuropathies, intraoperative EMG activity could be correlated in one of four sixth nerve injuries and four of five seventh nerve injuries. Electromyographic activity could not be correlated in four children with new neuropathies. Of 59 cranial nerves monitored that remained unchanged, 47 had no EMG activity. Twelve cranial nerves (three sixth nerves and nine seventh nerves) had EMG activity but no deficit. Of four children with lateral rectus EMG activity, three had new seventh nerve injuries.

Lateral rectus EMG activity did not predict postoperative abducens injury. The absence of lateral rectus EMG activity did not assure preserved abducens function postoperatively. Likely because of the close apposition of the intrapontine facial nerve to the abducens nucleus, lateral rectus EMG activity was highly predictive of seventh nerve injury. Although facial muscle EMG activity was not an absolute predictor of postoperative facial nerve dysfunction, the presence of facial muscle EMG activity was associated statistically with postoperative facial paresis. The absence of facial muscle EMG activity was rarely associated with facial nerve injury. The authors speculate that EMG activity in the facial muscles may have provided important intraoperative information to the surgeon so as to avoid facial nerve injury.