Thomas Menovsky

Endoscope-assisted Supraorbital Craniotomy for Lesions of the Interpeduncular Fossa

OBJECTIVE The supraorbital approach is well accepted for lesions in the anterior fossa, the sellar region, and the anterior circle of Willis. However, the usefulness of this approach has not yet been elucidated for lesions in the interpeduncular fossa. The technique of an endoscope-assisted, ipsi- and contralateral supraorbital approach to lesions within the interpeduncular fossa is described, and the initial results are reported. METHODS A small supraorbital craniotomy, using an eyebrow incision, was performed in each of seven patients who were operated on for different types of lesions in the interpeduncular fossa, including a neuromuscular choristoma of the oculomotor nerve, a retrosellar epidermoid tumor, and five aneurysms (two of the basilar artery tip, two at the offspring of the superior cerebellar artery, and one fusiform arterial widening of the basilar artery apex). The surgical approach, its indications and limitations, and the additional value of an endoscope are outlined. RESULTS All lesions could be easily reached and well visualized through this approach by using an endoscope as an adjunct to the operating microscope. The saccular aneurysms all could be clipped successfully, the fusiform widening was wrapped, the epidermoid tumor was removed completely, and the choristoma was removed only partially because of brain stem invasion. The patient with the neuromuscular choristoma had persistent diabetes insipidus postoperatively, most probably caused by stretching the pituitary stalk with the endoscope. The patient with the epidermoid tumor showed a postoperative transient partial oculomotor nerve paresis at the side of the approach. The cosmetic results of the eyebrow incisions for this approach were excellent in all patients. CONCLUSION Lesions in the interpeduncular fossa can be effectively treated using a supraorbital approach, which can be ipsi- or contralateral to the side of the lesion, depending on the exact location of the lesion. The use of an endoscope is essential to visualize these lesions that lie in the shadow of the sellar and parasellar anatomic structures. The major advantage over other approaches are a nearly perpendicular surgical route (although the distance is longer, which is, on the other hand, not a disadvantage), a minimized amount of dissection and brain retraction by using an endoscope through anatomic gateways, and a small surgical incision with excellent cosmetic results.

Cerebral arteriovenous malformations in childhood: state of the art with special reference to treatment

Abstract In this state of the art paper, the clinical and diagnostic features of cerebral arteriovenous malformation (AVM) in childhood are outlined and special attention is paid to the treatment. Several options exists for the treatment of an AVM, consisting of surgery, endovascular embolization, stereotactic radiosurgery, or a combination of these treatments.

Interstitial laser thermotherapy in neurosurgery : A review

SummaryOne of the most recent laser treatment modalities in neurosurgery is interstitial laser thermotherapy (ILTT). In this review, experimental and clinical studies concerning intracranial ILTT are discussed. Two methods for intra-operative control of the laser induced lesions are described; i.e., computer-controlled power delivery, using a thermocouple that is positioned interstitially at the periphery of the tumour to maintain the desired temperature at that point, and MRI, to visualise the extent of the thermal lesions induced by ILTT. The results show that ILTT using a Nd:YAG laser is easy and relatively effective in the treatment of small deepseated brain tumours with minimal risk and complications. This review is concluded with suggestions for further improvement of this treatment modality.

Laser tissue welding of dura mater and peripheral nerves : A scanning electron microscopy study

In order to elucidate the mechanism of tissue welding, scanning electron microscopy (SEM) was used to investigate the ultrastructural changes on the surface of dura mater and peripheral nerves after CO2 laser welding.

Light Propagation in the Brain Depends on Nerve Fiber Orientation

In this study, the penetration of red laser light (632.8 nm) in fresh bovine brain was measured parallel, oblique, and perpendicular to the axis of white matter tracts. The measurements were performed in eight samples with an isotropic light source and detector and were obtained by advancing the detector tip toward the light source in the tissue. A statistically significant difference in the effective attenuation coefficient of the light (mueff) was found between the parallel and perpendicular directions, 0.47 +/- 0.06 mm -1 and 0.63 +/- 0.13 mm-1, respectively (P = 0.005). The measurements taken at an angle of 45 degrees in the same sample resulted in an intermediate mueff of 0.58 +/- 0.09 mm-1. These results suggest a preferential guidance of light along the axis of the white matter tracts of the brain.

Laser(-assisted) nerve repair. A review

Over the last decade low power laser irradiation has been used to repair nerves by photothermal welding. Nineteen animal and clinical experimental studies of laser tissue welding of nerves are reviewed. Possible mechanisms of tissue welding are presented, together with the benefits, limitations, and possible future implications of several techniques used in laser nerve repair. The consensus of these studies is that nerve welding has some advantages over standard suture repair. These advantages include less neuroma- und scar formation and shorter repair time. The major disadvantage of laser nerve repair is the initial inferior tensile strength. In the future, use of dyes or proteins could enhance the welding process by reinforcing the union strength, thus may improve the results of this promising technique.

Effect of CO2 milliwatt laser on peripheral nerves: Part I. A dose-response study.

In order to explore further the role of laser for microneural repair, the effect of CO2 laser irradiation on intact rat sciatic nerves was investigated. In total 40 rat sciatic nerves were exposed to 12 different combinations of laser power (50, 100, and 150 mW) and pulse duration (0.1 to 3 s) normally used for CO2 laser‐assisted nerve repair. The results were evaluated 24 hr after surgery with functional toe‐spreading test and light microscopy. Irradiations of 50 and 100 mW for up to 1 s exposure time per pulse resulted in almost no deficit in motor function, while 100 mW power with prolonged exposure times and 150 mW power resulted in a significant decrease in motor function. Light microscopy showed significant focal injury to the epi/perineurium and the subepineunal nerve fibres proportional to the laser energy applied to the nerve, consisting of Wallerian degeneration and thrombosis of blood vessels. In conclusion, a power of 50–100 mW in combination with a pulse duration of 0.1–1 s produced no or minimal thermal damage with no or a negligible loss of motor function. Therefore, combinations of power and pulse duration above these thresholds are considered less suitable for CO2 laser nerve repair. MICROSURGERY 17:562–567 1996

Intraoperative values of S-100 protein, myelin basic protein,lactate, and albumin in the CSF and serum of neurosurgical patients

OBJECTIVES To assess the concentrations of S-100 protein, myelin basic protein (MBP), and lactate, and the (CSF)/serum albumin ratio (Qalb) during intracranial neurosurgical procedures. METHODS Samples of CSF from 91 patients with various CNS diseases were obtained by aspiration of cisternal CSF at the beginning of surgery (before starting surgical manipulation of the brain) and concentrations of S-100 protein, MBP, and lactate, and Qalb were determined. At the same time blood was sampled for determination of serum S-100 protein concentration. Patients were divided into three groups according to the aetiology of their CNS disease (intracranial haemorrhage, n=11; benign intracranial mass lesion, n=52; malignant neoplastic disease, n=28). Radiological and intraoperative characteristics were documented. RESULTS In each of these three groups median values of all four CSF variables measured were raised. The occurrence of brain oedema and a midline shift correlated significantly with raised concentrations of MBP and Qalb. Breaching of the arachnoid layer, documented at surgery for benign lesions, correlated with higher concentrations of MBP, lactate, CSF S-100 protein, and Qalb. CONCLUSIONS Intraoperative values of S-100 protein, MBP, lactate, and Qalb are increased in patients with intracranial haemorrhage, benign intracranial mass lesion, and malignant neoplastic disease. Breaching of the arachnoid layer and oedema is associated with higher concentrations of some of the aforementioned proteins. These biochemical data can serve as a basis for further research into CSF specific proteins.

Effect of CO2-milliwatt laser on peripheral nerves: Part II. A histological and functional study †

In order to further explore the role of laser for microneural repair, the early and late effects of CO2 laser irradiation on intact rat sciatic nerves were investigated. A total of 48 rat sciatic nerves were exposed to 100‐mW laser power with a pulse duration of 1.0 s and a spot size of 320 μm. In one‐half of the nerves, albumin solder was applied to the nerve followed by laser irradiation. The results were evaluated up to 94 days after surgery with functional toe‐spreading test, and light and transmission electron microscopy. Irradiation of the nerve resulted in almost no deficit in the motor function. A subperineurial degeneration of myelinated and unmyelinated axons is observed in the first 2 weeks after laser irradiation, while the central part of the nerve remains undamaged. The degeneration is followed by axonal regeneration with subsequent maturation of nerve fibres in time. No excessive intraneural or extraneural scarring was seen. In the soldered nerves, the solder elicits an inflammatory reaction upon the epineurium in the first week after irradiation. By week 1, the solder is completely absorbed. After 2 weeks, the inflammatory reaction ceases and by week 4, no residual reaction is seen. At 12 weeks, only minimally disarranged epineurium is seen with otherwise normal neural architecture. In conclusion, CO2 laser irradiation at 100 mW with pulses of 1.0 s has no long term negative effects on nerve function and morphology. Therefore, these laser settings can be safely applied for laser‐assisted nerve repair.

Effect of the CO2 milliwatt laser on tensile strength of microsutures

Laser‐assisted tissue repair is often accompanied by a high dehiscence rate, which may be due to alterations in suture material after laser exposure. The goal of this study was to investigate the effect of CO2 laser irradiation on the tensile strength of microsurgical suture material.